TSK-1769: TaskQuery on CustomFields distinguishes between empty / null.

common/taskana-common-data/src/main/resources/sql/test-data/task.sql

@@ -24,7 +24,7 @@ INSERT INTO TASK VALUES('TKI:000000000000000000000000000000000020', 'ETI:0000000
 INSERT INTO TASK VALUES('TKI:000000000000000000000000000000000021', 'ETI:000000000000000000000000000000000021', '2018-01-29 15:55:21', null                 , null                 , '2018-01-29 15:55:21', null                 , '2018-01-29 15:55:00', '2018-01-30 15:55:00', 'Widerruf'                , 'creator_user_id'            , 'Widerruf'                                 , null                                     , 2       , -1             , 'READY'     , 'EXTERN'                 , 'L1050'           , 'CLI:100000000000000000000000000000000003', 'WBI:100000000000000000000000000000000001' , 'GPK_KSC'     , 'DOMAIN_A', 'PI_0000000000021' , 'DOC_0000000000000000021' , null        , '00'        , 'PASystem' , '00'               , 'SDNR'   , '11223344'     , false  , false         , null         , 'NONE'          , null              , ''          , ''          , ''         , ''         , ''         , ''         , ''         , ''         , ''         , ''         , ''          , ''          , ''          , 'abc'    , ''          , ''         , 1           , 2           , 3           , 4           , 5           , 6           , 7           , 8   );
 INSERT INTO TASK VALUES('TKI:000000000000000000000000000000000022', 'ETI:000000000000000000000000000000000022', '2018-01-29 15:55:22', null                 , null                 , '2018-01-29 15:55:22', null                 , '2018-01-29 15:55:00', '2018-01-30 15:55:00', 'Widerruf'                , 'creator_user_id'            , 'Widerruf'                                 , null                                     , 2       , -1             , 'READY'     , 'EXTERN'                 , 'L1050'           , 'CLI:100000000000000000000000000000000003', 'WBI:100000000000000000000000000000000001' , 'GPK_KSC'     , 'DOMAIN_A', 'PI_0000000000022' , 'DOC_0000000000000000022' , null        , '00'        , 'PASystem' , '00'               , 'SDNR'   , '11223344'     , false  , false         , null         , 'NONE'          , null              , ''          , ''          , ''         , ''         , ''         , ''         , ''         , ''         , ''         , ''         , ''          , ''          , ''          , 'abc'    , ''          , ''         , 1           , 2           , 3           , 4           , 5           , 6           , 7           , 8   );
 INSERT INTO TASK VALUES('TKI:000000000000000000000000000000000023', 'ETI:000000000000000000000000000000000023', '2018-01-29 15:55:23', null                 , null                 , '2018-01-29 15:55:23', null                 , '2018-01-29 15:55:00', '2018-01-30 15:55:00', 'Widerruf'                , 'creator_user_id'            , 'Widerruf'                                 , null                                     , 2       , -1             , 'READY'     , 'EXTERN'                 , 'L1050'           , 'CLI:100000000000000000000000000000000003', 'WBI:100000000000000000000000000000000001' , 'GPK_KSC'     , 'DOMAIN_A', 'PI_0000000000023' , 'DOC_0000000000000000023' , null        , '00'        , 'PASystem' , '00'               , 'SDNR'   , '11223344'     , false  , false         , null         , 'NONE'          , null              , ''          , ''          , ''         , ''         , ''         , ''         , ''         , 'lnp'      , ''         , ''         , ''          , ''          , ''          , 'abc'    , ''          , ''         , 1           , 2           , 3           , 4           , 5           , 6           , 7           , 8   );
-INSERT INTO TASK VALUES('TKI:000000000000000000000000000000000024', 'ETI:000000000000000000000000000000000024', '2018-01-29 15:55:24', null                 , null                 , '2018-01-29 15:55:24', null                 , '2018-01-29 15:55:00', '2018-01-30 15:55:00', 'Widerruf'                , 'creator_user_id'            , 'Widerruf'                                 , null                                     , 2       , -1             , 'READY'     , 'EXTERN'                 , 'L1050'           , 'CLI:100000000000000000000000000000000003', 'WBI:100000000000000000000000000000000001' , 'GPK_KSC'     , 'DOMAIN_A', 'PI_0000000000024' , 'DOC_0000000000000000024' , null        , '00'        , 'PASystem' , '00'               , 'SDNR'   , '11223344'     , false  , false         , null         , 'NONE'          , null              , ''          , ''          , ''         , ''         , ''         , ''         , ''         , ''         , ''         , ''         , ''          , ''          , ''          , 'abc'    , ''          , ''         , 1           , 2           , 3           , 4           , 5           , 6           , 7           , 8   );
+INSERT INTO TASK VALUES('TKI:000000000000000000000000000000000024', 'ETI:000000000000000000000000000000000024', '2018-01-29 15:55:24', null                 , null                 , '2018-01-29 15:55:24', null                 , '2018-01-29 15:55:00', '2018-01-30 15:55:00', 'Widerruf'                , 'creator_user_id'            , 'Widerruf'                                 , null                                     , 2       , -1             , 'READY'     , 'EXTERN'                 , 'L1050'           , 'CLI:100000000000000000000000000000000003', 'WBI:100000000000000000000000000000000001' , 'GPK_KSC'     , 'DOMAIN_A', 'PI_0000000000024' , 'DOC_0000000000000000024' , null        , '00'        , 'PASystem' , '00'               , 'SDNR'   , '11223344'     , false  , false         , null         , 'NONE'          , null              , ''          , ''          , ''         , ''         , ''         , ''         , ''         , ''         , null       , ''         , ''          , ''          , ''          , 'abc'    , ''          , ''         , 1           , 2           , 3           , 4           , 5           , 6           , 7           , 8   );
 -- Tasks for WorkOnTaskAccTest
 INSERT INTO TASK VALUES('TKI:000000000000000000000000000000000025', 'ETI:000000000000000000000000000000000025', '2018-01-29 15:55:24', null                 , null                 , '2018-01-29 15:55:24', '2018-01-29 15:55:24', '2018-01-29 15:55:00', '2018-01-30 15:55:00', 'Widerruf'                , 'creator_user_id'            , 'Widerruf'                                 , null                                     , 2       , -1             , 'READY'     , 'EXTERN'                 , 'L1050'           , 'CLI:100000000000000000000000000000000003', 'WBI:100000000000000000000000000000000007' , 'USER-1-2'    , 'DOMAIN_A', 'PI_0000000000025' , 'DOC_0000000000000000025' , null        , 'abcd00'    , 'PASystem' , '00'               , 'SDNR'   , '98765432'     , false  , false         , null         , 'NONE'          , null              , ''          , ''          , ''         , ''         , ''         , ''         , ''         , ''         , ''         , 'ert'      , 'ert'       , 'ert'       , 'ert'       , 'abc'    , 'ert'       , 'ert'      , 1           , 2           , 3           , 4           , 5           , 6           , 7           , 8   );
 INSERT INTO TASK VALUES('TKI:000000000000000000000000000000000026', 'ETI:000000000000000000000000000000000026', '2018-01-29 15:55:24', '2018-01-30 15:55:24', null                 , '2018-01-30 15:55:24', '2018-01-29 15:55:24', '2018-01-29 15:55:00', '2018-01-30 15:55:00', 'Widerruf'                , 'creator_user_id'            , 'Widerruf'                                 , null                                     , 2       , -1             , 'CLAIMED'   , 'EXTERN'                 , 'L1050'           , 'CLI:100000000000000000000000000000000003', 'WBI:100000000000000000000000000000000007' , 'USER-1-2'    , 'DOMAIN_A', 'PI_0000000000026' , 'DOC_0000000000000000026' , 'user-1-1'  , 'bcde00'    , 'PASystem' , '00'               , 'SDNR'   , '98765432'     , true   , false         , null         , 'NONE'          , null              , ''          , ''          , ''         , ''         , ''         , ''         , ''         , ''         , ''         , ''         , ''          , ''          , ''          , 'abc'    , ''          , ''         , 1           , 2           , 3           , 4           , 5           , 6           , 7           , 8   );

common/taskana-common/src/main/java/pro/taskana/common/internal/util/SqlProviderUtil.java

@@ -12,13 +12,22 @@ public class SqlProviderUtil {
   private SqlProviderUtil() {}
 
   public static StringBuilder whereIn(String collection, String column, StringBuilder sb) {
-    return sb.append("<if test='")
+    sb.append("<if test='")
         .append(collection)
-        .append(" != null'>AND ")
+        .append(" != null'>AND (")
+        .append("<choose>")
+        .append("<when test='" + collection + ".length > 0'>")
         .append(column)
         .append(" IN(<foreach item='item' collection='")
         .append(collection)
-        .append("' separator=',' >#{item}</foreach>)</if> ");
+        .append("' separator=',' >#{item}</foreach>)")
+        .append("</when>")
+        .append("<otherwise>0=1</otherwise>")
+        .append("</choose>");
+    if (column.contains("t.CUSTOM_")) {
+      sb.append("<if test='" + collection + "ContainsNull'> OR " + column + " IS NULL </if>");
+    }
+    return sb.append(")</if> ");
   }
 
   public static StringBuilder whereIn(String collection, String column) {
@@ -26,13 +35,24 @@ public class SqlProviderUtil {
   }
 
   public static StringBuilder whereNotIn(String collection, String column, StringBuilder sb) {
-    return sb.append("<if test='")
+    sb.append("<if test='")
         .append(collection)
-        .append(" != null'>AND ")
+        .append(" != null'>AND (")
+        .append("<choose>")
+        .append("<when test='" + collection + ".length > 0'>")
         .append(column)
         .append(" NOT IN(<foreach item='item' collection='")
         .append(collection)
-        .append("' separator=',' >#{item}</foreach>)</if> ");
+        .append("' separator=',' >#{item}</foreach>)")
+        .append("</when>")
+        .append("<otherwise>1=1</otherwise>")
+        .append("</choose>");
+    if (column.contains("t.CUSTOM_")) {
+      sb.append("<if test='" + collection + "ContainsNull'> AND " + column + " IS NOT NULL </if>");
+      sb.append("<if test='!" + collection + "ContainsNull'> OR " + column + " IS NULL </if>");
+    }
+    sb.append(")</if> ");
+    return sb;
   }
 
   public static StringBuilder whereNotIn(String collection, String column) {

lib/taskana-core/src/main/java/pro/taskana/classification/internal/models/ClassificationImpl.java

@@ -83,9 +83,6 @@ public class ClassificationImpl extends ClassificationSummaryImpl implements Cla
 
   @Override
   public void setCustomAttribute(ClassificationCustomField customField, String value) {
-    if (value == null) {
-      value = "";
-    }
     switch (customField) {
       case CUSTOM_1:
         custom1 = value;

lib/taskana-core/src/main/java/pro/taskana/classification/internal/models/ClassificationSummaryImpl.java

@@ -20,14 +20,14 @@ public class ClassificationSummaryImpl implements ClassificationSummary {
   protected int priority;
   protected String serviceLevel; // PddDThhHmmM
   protected String type;
-  protected String custom1 = "";
+  protected String custom1;
-  protected String custom2 = "";
+  protected String custom2;
-  protected String custom3 = "";
+  protected String custom3;
-  protected String custom4 = "";
+  protected String custom4;
-  protected String custom5 = "";
+  protected String custom5;
-  protected String custom6 = "";
+  protected String custom6;
-  protected String custom7 = "";
+  protected String custom7;
-  protected String custom8 = "";
+  protected String custom8;
 
   public ClassificationSummaryImpl() {}
 
@@ -179,11 +179,7 @@ public class ClassificationSummaryImpl implements ClassificationSummary {
   }
 
   public void setCustom1(String custom1) {
-    if (custom1 == null) {
+    this.custom1 = custom1;
-      this.custom1 = "";
-    } else {
-      this.custom1 = custom1;
-    }
   }
 
   public String getCustom2() {
@@ -191,11 +187,7 @@ public class ClassificationSummaryImpl implements ClassificationSummary {
   }
 
   public void setCustom2(String custom2) {
-    if (custom2 == null) {
+    this.custom2 = custom2;
-      this.custom2 = "";
-    } else {
-      this.custom2 = custom2;
-    }
   }
 
   public String getCustom3() {
@@ -203,11 +195,7 @@ public class ClassificationSummaryImpl implements ClassificationSummary {
   }
 
   public void setCustom3(String custom3) {
-    if (custom3 == null) {
+    this.custom3 = custom3;
-      this.custom3 = "";
-    } else {
-      this.custom3 = custom3;
-    }
   }
 
   public String getCustom4() {
@@ -215,11 +203,7 @@ public class ClassificationSummaryImpl implements ClassificationSummary {
   }
 
   public void setCustom4(String custom4) {
-    if (custom4 == null) {
+    this.custom4 = custom4;
-      this.custom4 = "";
-    } else {
-      this.custom4 = custom4;
-    }
   }
 
   public String getCustom5() {
@@ -227,11 +211,7 @@ public class ClassificationSummaryImpl implements ClassificationSummary {
   }
 
   public void setCustom5(String custom5) {
-    if (custom5 == null) {
+    this.custom5 = custom5;
-      this.custom5 = "";
-    } else {
-      this.custom5 = custom5;
-    }
   }
 
   public String getCustom6() {
@@ -239,11 +219,7 @@ public class ClassificationSummaryImpl implements ClassificationSummary {
   }
 
   public void setCustom6(String custom6) {
-    if (custom6 == null) {
+    this.custom6 = custom6;
-      this.custom6 = "";
-    } else {
-      this.custom6 = custom6;
-    }
   }
 
   public String getCustom7() {
@@ -251,11 +227,7 @@ public class ClassificationSummaryImpl implements ClassificationSummary {
   }
 
   public void setCustom7(String custom7) {
-    if (custom7 == null) {
+    this.custom7 = custom7;
-      this.custom7 = "";
-    } else {
-      this.custom7 = custom7;
-    }
   }
 
   public String getCustom8() {
@@ -263,11 +235,7 @@ public class ClassificationSummaryImpl implements ClassificationSummary {
   }
 
   public void setCustom8(String custom8) {
-    if (custom8 == null) {
+    this.custom8 = custom8;
-      this.custom8 = "";
-    } else {
-      this.custom8 = custom8;
-    }
   }
 
   @Override

lib/taskana-core/src/main/java/pro/taskana/monitor/internal/MonitorMapper.java

@@ -89,9 +89,9 @@ public interface MonitorMapper {
   @Result(column = "STATE", property = "state")
   @Result(column = "COUNT", property = "count")
   List<TaskQueryItem> getTasksCountByState(
-      @Param("domains") List<String> domains,
+      @Param("domains") String[] domains,
-      @Param("states") List<TaskState> states,
+      @Param("states") TaskState[] states,
-      @Param("workbasketIds") List<String> workbasketIds,
+      @Param("workbasketIds") String[] workbasketIds,
       @Param("priorityMinimum") Integer priorityMinimum);
 
   @SelectProvider(

lib/taskana-core/src/main/java/pro/taskana/monitor/internal/reports/ClassificationReportBuilderImpl.java

@@ -62,7 +62,7 @@ public class ClassificationReportBuilderImpl
                   report.getRows().isEmpty()
                       ? null
                       : report.getRows().keySet().toArray(new String[0]))
-              .domainIn(domains != null ? domains.toArray(new String[0]) : null)
+              .domainIn(this.domains)
               .list()
               .stream()
               .collect(
@@ -106,7 +106,7 @@ public class ClassificationReportBuilderImpl
           classificationService
               .createClassificationQuery()
               .keyIn(keys.length == 0 ? null : keys)
-              .domainIn(domains != null ? domains.toArray(new String[0]) : null)
+              .domainIn(this.domains)
               .list()
               .stream()
               .collect(

lib/taskana-core/src/main/java/pro/taskana/monitor/internal/reports/TaskStatusReportBuilderImpl.java

@@ -1,5 +1,6 @@
 package pro.taskana.monitor.internal.reports;
 
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
@@ -21,9 +22,9 @@ public class TaskStatusReportBuilderImpl implements TaskStatusReport.Builder {
   private final InternalTaskanaEngine taskanaEngine;
   private final MonitorMapper monitorMapper;
   private final WorkbasketService workbasketService;
-  private List<String> domains;
+  private String[] domains;
-  private List<TaskState> states;
+  private TaskState[] states;
-  private List<String> workbasketIds;
+  private String[] workbasketIds;
   private Integer priorityMinimum;
 
   public TaskStatusReportBuilderImpl(
@@ -41,7 +42,8 @@ public class TaskStatusReportBuilderImpl implements TaskStatusReport.Builder {
       List<TaskQueryItem> tasks =
           this.monitorMapper.getTasksCountByState(
               this.domains, this.states, this.workbasketIds, this.priorityMinimum);
-      TaskStatusReport report = new TaskStatusReport(this.states);
+      TaskStatusReport report =
+          new TaskStatusReport(this.states != null ? Arrays.asList(this.states) : null);
       report.addItems(tasks);
       Map<String, String> displayMap =
           taskanaEngine
@@ -51,7 +53,7 @@ public class TaskStatusReportBuilderImpl implements TaskStatusReport.Builder {
                       workbasketService
                           .createWorkbasketQuery()
                           .keyIn(report.getRows().keySet().toArray(new String[0]))
-                          .domainIn(domains != null ? domains.toArray(new String[0]) : null)
+                          .domainIn(domains)
                           .list()
                           .stream()
                           .collect(
@@ -68,7 +70,9 @@ public class TaskStatusReportBuilderImpl implements TaskStatusReport.Builder {
 
   @Override
   public TaskStatusReportBuilderImpl stateIn(List<TaskState> states) {
-    this.states = states;
+    if (states != null) {
+      this.states = states.toArray(new TaskState[0]);
+    }
     return this;
   }
 
@@ -80,13 +84,17 @@ public class TaskStatusReportBuilderImpl implements TaskStatusReport.Builder {
 
   @Override
   public TaskStatusReportBuilderImpl domainIn(List<String> domains) {
-    this.domains = domains;
+    if (domains != null) {
+      this.domains = domains.toArray(new String[0]);
+    }
     return this;
   }
 
   @Override
   public Builder workbasketIdsIn(List<String> workbasketIds) {
-    this.workbasketIds = workbasketIds;
+    if (workbasketIds != null) {
+      this.workbasketIds = workbasketIds.toArray(new String[0]);
+    }
     return this;
   }
 }

lib/taskana-core/src/main/java/pro/taskana/monitor/internal/reports/TimeIntervalReportBuilderImpl.java

@@ -1,7 +1,6 @@
 package pro.taskana.monitor.internal.reports;
 
 import java.time.Instant;
-import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.stream.Collectors;
@@ -41,12 +40,12 @@ abstract class TimeIntervalReportBuilderImpl<
   protected MonitorMapper monitorMapper;
   protected List<H> columnHeaders;
   protected boolean inWorkingDays;
-  protected List<String> workbasketIds;
+  protected String[] workbasketIds;
-  protected List<TaskState> states;
+  protected TaskState[] states;
-  protected List<String> classificationCategories;
+  protected String[] classificationCategories;
-  protected List<String> domains;
+  protected String[] domains;
-  protected List<String> classificationIds;
+  protected String[] classificationIds;
-  protected List<String> excludedClassificationIds;
+  protected String[] excludedClassificationIds;
   protected WorkingDaysToDaysConverter converter;
   private String[] custom1In;
   private String[] custom1NotIn;
@@ -118,37 +117,49 @@ abstract class TimeIntervalReportBuilderImpl<
 
   @Override
   public B workbasketIdIn(List<String> workbasketIds) {
-    this.workbasketIds = new ArrayList<>(workbasketIds);
+    if (workbasketIds != null) {
+      this.workbasketIds = workbasketIds.toArray(new String[0]);
+    }
     return _this();
   }
 
   @Override
   public B stateIn(List<TaskState> states) {
-    this.states = new ArrayList<>(states);
+    if (states != null) {
+      this.states = states.toArray(new TaskState[0]);
+    }
     return _this();
   }
 
   @Override
   public B classificationCategoryIn(List<String> classificationCategories) {
-    this.classificationCategories = new ArrayList<>(classificationCategories);
+    if (classificationCategories != null) {
+      this.classificationCategories = classificationCategories.toArray(new String[0]);
+    }
     return _this();
   }
 
   @Override
   public B classificationIdIn(List<String> classificationIds) {
-    this.classificationIds = new ArrayList<>(classificationIds);
+    if (classificationIds != null) {
+      this.classificationIds = classificationIds.toArray(new String[0]);
+    }
     return _this();
   }
 
   @Override
   public B excludedClassificationIdIn(List<String> excludedClassificationIds) {
-    this.excludedClassificationIds = new ArrayList<>(excludedClassificationIds);
+    if (excludedClassificationIds != null) {
+      this.excludedClassificationIds = excludedClassificationIds.toArray(new String[0]);
+    }
     return _this();
   }
 
   @Override
   public B domainIn(List<String> domains) {
-    this.domains = new ArrayList<>(domains);
+    if (domains != null) {
+      this.domains = domains.toArray(new String[0]);
+    }
     return _this();
   }
 

lib/taskana-core/src/main/java/pro/taskana/monitor/internal/reports/WorkbasketPriorityReportBuilderImpl.java

@@ -1,6 +1,5 @@
 package pro.taskana.monitor.internal.reports;
 
-import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
@@ -25,12 +24,12 @@ public class WorkbasketPriorityReportBuilderImpl implements WorkbasketPriorityRe
   private final MonitorMapper monitorMapper;
   protected List<PriorityColumnHeader> columnHeaders;
   protected boolean inWorkingDays;
-  protected List<String> workbasketIds;
+  protected String[] workbasketIds;
-  protected List<TaskState> states;
+  protected TaskState[] states;
-  protected List<String> classificationCategories;
+  protected String[] classificationCategories;
-  protected List<String> domains;
+  protected String[] domains;
-  protected List<String> classificationIds;
+  protected String[] classificationIds;
-  protected List<String> excludedClassificationIds;
+  protected String[] excludedClassificationIds;
   protected WorkingDaysToDaysConverter converter;
   private WorkbasketType[] workbasketTypes;
   private String[] custom1In;
@@ -121,37 +120,49 @@ public class WorkbasketPriorityReportBuilderImpl implements WorkbasketPriorityRe
 
   @Override
   public Builder workbasketIdIn(List<String> workbasketIds) {
-    this.workbasketIds = new ArrayList<>(workbasketIds);
+    if (workbasketIds != null) {
+      this.workbasketIds = workbasketIds.toArray(new String[0]);
+    }
     return this;
   }
 
   @Override
   public Builder stateIn(List<TaskState> states) {
-    this.states = new ArrayList<>(states);
+    if (states != null) {
+      this.states = states.toArray(new TaskState[0]);
+    }
     return this;
   }
 
   @Override
   public Builder classificationCategoryIn(List<String> classificationCategories) {
-    this.classificationCategories = new ArrayList<>(classificationCategories);
+    if (classificationCategories != null) {
+      this.classificationCategories = classificationCategories.toArray(new String[0]);
+    }
     return this;
   }
 
   @Override
   public Builder classificationIdIn(List<String> classificationIds) {
-    this.classificationIds = new ArrayList<>(classificationIds);
+    if (classificationIds != null) {
+      this.classificationIds = classificationIds.toArray(new String[0]);
+    }
     return this;
   }
 
   @Override
   public Builder excludedClassificationIdIn(List<String> excludedClassificationIds) {
-    this.excludedClassificationIds = new ArrayList<>(excludedClassificationIds);
+    if (excludedClassificationIds != null) {
+      this.excludedClassificationIds = excludedClassificationIds.toArray(new String[0]);
+    }
     return this;
   }
 
   @Override
   public Builder domainIn(List<String> domains) {
-    this.domains = new ArrayList<>(domains);
+    if (domains != null) {
+      this.domains = domains.toArray(new String[0]);
+    }
     return this;
   }
 

lib/taskana-core/src/main/java/pro/taskana/monitor/internal/reports/WorkbasketReportBuilderImpl.java

@@ -60,7 +60,7 @@ public class WorkbasketReportBuilderImpl
                       workbasketService
                           .createWorkbasketQuery()
                           .keyIn(report.getRows().keySet().toArray(new String[0]))
-                          .domainIn(domains != null ? domains.toArray(new String[0]) : null)
+                          .domainIn(domains)
                           .list()
                           .stream()
                           .collect(

lib/taskana-core/src/main/java/pro/taskana/task/internal/TaskQueryImpl.java

@@ -257,67 +257,99 @@ public class TaskQueryImpl implements TaskQuery {
   // endregion
   // region customAttributes
   private String[] custom1In;
+  private boolean custom1InContainsNull;
   private String[] custom1NotIn;
+  private boolean custom1NotInContainsNull;
   private String[] custom1Like;
   private String[] custom1NotLike;
   private String[] custom2In;
+  private boolean custom2InContainsNull;
   private String[] custom2NotIn;
+  private boolean custom2NotInContainsNull;
   private String[] custom2Like;
   private String[] custom2NotLike;
   private String[] custom3In;
+  private boolean custom3InContainsNull;
   private String[] custom3NotIn;
+  private boolean custom3NotInContainsNull;
   private String[] custom3Like;
   private String[] custom3NotLike;
   private String[] custom4In;
+  private boolean custom4InContainsNull;
   private String[] custom4NotIn;
+  private boolean custom4NotInContainsNull;
   private String[] custom4Like;
   private String[] custom4NotLike;
   private String[] custom5In;
+  private boolean custom5InContainsNull;
   private String[] custom5NotIn;
+  private boolean custom5NotInContainsNull;
   private String[] custom5Like;
   private String[] custom5NotLike;
   private String[] custom6In;
+  private boolean custom6InContainsNull;
   private String[] custom6NotIn;
+  private boolean custom6NotInContainsNull;
   private String[] custom6Like;
   private String[] custom6NotLike;
   private String[] custom7In;
+  private boolean custom7InContainsNull;
   private String[] custom7NotIn;
+  private boolean custom7NotInContainsNull;
   private String[] custom7Like;
   private String[] custom7NotLike;
   private String[] custom8In;
+  private boolean custom8InContainsNull;
   private String[] custom8NotIn;
+  private boolean custom8NotInContainsNull;
   private String[] custom8Like;
   private String[] custom8NotLike;
   private String[] custom9In;
+  private boolean custom9InContainsNull;
   private String[] custom9NotIn;
+  private boolean custom9NotInContainsNull;
   private String[] custom9Like;
   private String[] custom9NotLike;
   private String[] custom10In;
+  private boolean custom10InContainsNull;
   private String[] custom10NotIn;
+  private boolean custom10NotInContainsNull;
   private String[] custom10Like;
   private String[] custom10NotLike;
   private String[] custom11In;
+  private boolean custom11InContainsNull;
   private String[] custom11NotIn;
+  private boolean custom11NotInContainsNull;
   private String[] custom11Like;
   private String[] custom11NotLike;
   private String[] custom12In;
+  private boolean custom12InContainsNull;
   private String[] custom12NotIn;
+  private boolean custom12NotInContainsNull;
   private String[] custom12Like;
   private String[] custom12NotLike;
   private String[] custom13In;
+  private boolean custom13InContainsNull;
   private String[] custom13NotIn;
+  private boolean custom13NotInContainsNull;
   private String[] custom13Like;
   private String[] custom13NotLike;
   private String[] custom14In;
+  private boolean custom14InContainsNull;
   private String[] custom14NotIn;
+  private boolean custom14NotInContainsNull;
   private String[] custom14Like;
   private String[] custom14NotLike;
   private String[] custom15In;
+  private boolean custom15InContainsNull;
   private String[] custom15NotIn;
+  private boolean custom15NotInContainsNull;
   private String[] custom15Like;
   private String[] custom15NotLike;
   private String[] custom16In;
+  private boolean custom16InContainsNull;
   private String[] custom16NotIn;
+  private boolean custom16NotInContainsNull;
   private String[] custom16Like;
   private String[] custom16NotLike;
   // endregion
@@ -1363,54 +1395,109 @@ public class TaskQueryImpl implements TaskQuery {
       throw new InvalidArgumentException(
           "At least one string has to be provided as a search parameter");
     }
+
+    List<String> conditionList = new ArrayList<>(Arrays.asList(strings));
+    boolean containsNull = conditionList.contains(null);
+    if (containsNull) {
+      conditionList.remove(null);
+    }
+
     switch (customField) {
       case CUSTOM_1:
-        this.custom1In = strings;
+        this.custom1In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom1InContainsNull = true;
+        }
         break;
       case CUSTOM_2:
-        this.custom2In = strings;
+        this.custom2In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom2InContainsNull = true;
+        }
         break;
       case CUSTOM_3:
-        this.custom3In = strings;
+        this.custom3In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom3InContainsNull = true;
+        }
         break;
       case CUSTOM_4:
-        this.custom4In = strings;
+        this.custom4In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom4InContainsNull = true;
+        }
         break;
       case CUSTOM_5:
-        this.custom5In = strings;
+        this.custom5In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom5InContainsNull = true;
+        }
         break;
       case CUSTOM_6:
-        this.custom6In = strings;
+        this.custom6In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom6InContainsNull = true;
+        }
         break;
       case CUSTOM_7:
-        this.custom7In = strings;
+        this.custom7In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom7InContainsNull = true;
+        }
         break;
       case CUSTOM_8:
-        this.custom8In = strings;
+        this.custom8In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom8InContainsNull = true;
+        }
         break;
       case CUSTOM_9:
-        this.custom9In = strings;
+        this.custom9In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom9InContainsNull = true;
+        }
         break;
       case CUSTOM_10:
-        this.custom10In = strings;
+        this.custom10In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom10InContainsNull = true;
+        }
         break;
       case CUSTOM_11:
-        this.custom11In = strings;
+        this.custom11In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom11InContainsNull = true;
+        }
         break;
       case CUSTOM_12:
-        this.custom12In = strings;
+        this.custom12In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom12InContainsNull = true;
+        }
         break;
       case CUSTOM_13:
-        this.custom13In = strings;
+        this.custom13In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom13InContainsNull = true;
+        }
         break;
       case CUSTOM_14:
-        this.custom14In = strings;
+        this.custom14In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom14InContainsNull = true;
+        }
         break;
       case CUSTOM_15:
-        this.custom15In = strings;
+        this.custom15In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom15InContainsNull = true;
+        }
         break;
       case CUSTOM_16:
-        this.custom16In = strings;
+        this.custom16In = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom16InContainsNull = true;
+        }
         break;
       default:
         throw new SystemException("Unknown custom attribute '" + customField + "'");
@@ -1426,54 +1513,107 @@ public class TaskQueryImpl implements TaskQuery {
       throw new InvalidArgumentException(
           "At least one string has to be provided as a search parameter");
     }
+    List<String> conditionList = new ArrayList<>(Arrays.asList(strings));
+    boolean containsNull = conditionList.contains(null);
+    if (containsNull) {
+      conditionList.remove(null);
+    }
     switch (customField) {
       case CUSTOM_1:
-        this.custom1NotIn = strings;
+        this.custom1NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom1NotInContainsNull = true;
+        }
         break;
       case CUSTOM_2:
-        this.custom2NotIn = strings;
+        this.custom2NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom2NotInContainsNull = true;
+        }
         break;
       case CUSTOM_3:
-        this.custom3NotIn = strings;
+        this.custom3NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom3NotInContainsNull = true;
+        }
         break;
       case CUSTOM_4:
-        this.custom4NotIn = strings;
+        this.custom4NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom4NotInContainsNull = true;
+        }
         break;
       case CUSTOM_5:
-        this.custom5NotIn = strings;
+        this.custom5NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom5NotInContainsNull = true;
+        }
         break;
       case CUSTOM_6:
-        this.custom6NotIn = strings;
+        this.custom6NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom6NotInContainsNull = true;
+        }
         break;
       case CUSTOM_7:
-        this.custom7NotIn = strings;
+        this.custom7NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom7NotInContainsNull = true;
+        }
         break;
       case CUSTOM_8:
-        this.custom8NotIn = strings;
+        this.custom8NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom8NotInContainsNull = true;
+        }
         break;
       case CUSTOM_9:
-        this.custom9NotIn = strings;
+        this.custom9NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom9NotInContainsNull = true;
+        }
         break;
       case CUSTOM_10:
-        this.custom10NotIn = strings;
+        this.custom10NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom10NotInContainsNull = true;
+        }
         break;
       case CUSTOM_11:
-        this.custom11NotIn = strings;
+        this.custom11NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom11NotInContainsNull = true;
+        }
         break;
       case CUSTOM_12:
-        this.custom12NotIn = strings;
+        this.custom12NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom12NotInContainsNull = true;
+        }
         break;
       case CUSTOM_13:
-        this.custom13NotIn = strings;
+        this.custom13NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom13NotInContainsNull = true;
+        }
         break;
       case CUSTOM_14:
-        this.custom14NotIn = strings;
+        this.custom14NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom14NotInContainsNull = true;
+        }
         break;
       case CUSTOM_15:
-        this.custom15NotIn = strings;
+        this.custom15NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom15NotInContainsNull = true;
+        }
         break;
       case CUSTOM_16:
-        this.custom16NotIn = strings;
+        this.custom16NotIn = conditionList.toArray(new String[0]);
+        if (containsNull) {
+          this.custom16NotInContainsNull = true;
+        }
         break;
       default:
         throw new SystemException("Unknown custom attribute '" + customField + "'");

lib/taskana-core/src/main/java/pro/taskana/task/internal/models/TaskImpl.java

@@ -110,9 +110,6 @@ public class TaskImpl extends TaskSummaryImpl implements Task {
 
   @Override
   public void setCustomAttribute(TaskCustomField customField, String value) {
-    if (value == null) {
-      value = "";
-    }
     switch (customField) {
       case CUSTOM_1:
         custom1 = value;

lib/taskana-core/src/main/java/pro/taskana/task/internal/models/TaskSummaryImpl.java

@@ -46,22 +46,22 @@ public class TaskSummaryImpl implements TaskSummary {
   protected boolean isTransferred;
   // All objects have to be serializable
   protected List<AttachmentSummary> attachmentSummaries = new ArrayList<>();
-  protected String custom1 = "";
+  protected String custom1;
-  protected String custom2 = "";
+  protected String custom2;
-  protected String custom3 = "";
+  protected String custom3;
-  protected String custom4 = "";
+  protected String custom4;
-  protected String custom5 = "";
+  protected String custom5;
-  protected String custom6 = "";
+  protected String custom6;
-  protected String custom7 = "";
+  protected String custom7;
-  protected String custom8 = "";
+  protected String custom8;
-  protected String custom9 = "";
+  protected String custom9;
-  protected String custom10 = "";
+  protected String custom10;
-  protected String custom11 = "";
+  protected String custom11;
-  protected String custom12 = "";
+  protected String custom12;
-  protected String custom13 = "";
+  protected String custom13;
-  protected String custom14 = "";
+  protected String custom14;
-  protected String custom15 = "";
+  protected String custom15;
-  protected String custom16 = "";
+  protected String custom16;
 
   public TaskSummaryImpl() {}
 
@@ -422,11 +422,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom1(String custom1) {
-    if (custom1 == null) {
+    this.custom1 = custom1;
-      this.custom1 = "";
-    } else {
-      this.custom1 = custom1;
-    }
   }
 
   public String getCustom2() {
@@ -435,11 +431,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom2(String custom2) {
-    if (custom2 == null) {
+    this.custom2 = custom2;
-      this.custom2 = "";
-    } else {
-      this.custom2 = custom2;
-    }
   }
 
   public String getCustom3() {
@@ -448,11 +440,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom3(String custom3) {
-    if (custom3 == null) {
+    this.custom3 = custom3;
-      this.custom3 = "";
-    } else {
-      this.custom3 = custom3;
-    }
   }
 
   public String getCustom4() {
@@ -461,11 +449,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom4(String custom4) {
-    if (custom4 == null) {
+    this.custom4 = custom4;
-      this.custom4 = "";
-    } else {
-      this.custom4 = custom4;
-    }
   }
 
   public String getCustom5() {
@@ -474,11 +458,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom5(String custom5) {
-    if (custom5 == null) {
+    this.custom5 = custom5;
-      this.custom5 = "";
-    } else {
-      this.custom5 = custom5;
-    }
   }
 
   public String getCustom6() {
@@ -487,11 +467,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom6(String custom6) {
-    if (custom6 == null) {
+    this.custom6 = custom6;
-      this.custom6 = "";
-    } else {
-      this.custom6 = custom6;
-    }
   }
 
   public String getCustom7() {
@@ -500,11 +476,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom7(String custom7) {
-    if (custom7 == null) {
+    this.custom7 = custom7;
-      this.custom7 = "";
-    } else {
-      this.custom7 = custom7;
-    }
   }
 
   public String getCustom8() {
@@ -513,11 +485,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom8(String custom8) {
-    if (custom8 == null) {
+    this.custom8 = custom8;
-      this.custom8 = "";
-    } else {
-      this.custom8 = custom8;
-    }
   }
 
   public String getCustom9() {
@@ -526,11 +494,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom9(String custom9) {
-    if (custom9 == null) {
+    this.custom9 = custom9;
-      this.custom9 = "";
-    } else {
-      this.custom9 = custom9;
-    }
   }
 
   public String getCustom10() {
@@ -539,11 +503,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom10(String custom10) {
-    if (custom10 == null) {
+    this.custom10 = custom10;
-      this.custom10 = "";
-    } else {
-      this.custom10 = custom10;
-    }
   }
 
   public String getCustom11() {
@@ -552,11 +512,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom11(String custom11) {
-    if (custom11 == null) {
+    this.custom11 = custom11;
-      this.custom11 = "";
-    } else {
-      this.custom11 = custom11;
-    }
   }
 
   public String getCustom12() {
@@ -565,11 +521,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom12(String custom12) {
-    if (custom12 == null) {
+    this.custom12 = custom12;
-      this.custom12 = "";
-    } else {
-      this.custom12 = custom12;
-    }
   }
 
   public String getCustom13() {
@@ -578,11 +530,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom13(String custom13) {
-    if (custom13 == null) {
+    this.custom13 = custom13;
-      this.custom13 = "";
-    } else {
-      this.custom13 = custom13;
-    }
   }
 
   public String getCustom14() {
@@ -591,11 +539,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom14(String custom14) {
-    if (custom14 == null) {
+    this.custom14 = custom14;
-      this.custom14 = "";
-    } else {
-      this.custom14 = custom14;
-    }
   }
 
   public String getCustom15() {
@@ -604,11 +548,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom15(String custom15) {
-    if (custom15 == null) {
+    this.custom15 = custom15;
-      this.custom15 = "";
-    } else {
-      this.custom15 = custom15;
-    }
   }
 
   public String getCustom16() {
@@ -617,11 +557,7 @@ public class TaskSummaryImpl implements TaskSummary {
 
   // auxiliary Method needed by Mybatis
   public void setCustom16(String custom16) {
-    if (custom16 == null) {
+    this.custom16 = custom16;
-      this.custom16 = "";
-    } else {
-      this.custom16 = custom16;
-    }
   }
 
   protected boolean canEqual(Object other) {

lib/taskana-core/src/main/java/pro/taskana/workbasket/internal/models/WorkbasketImpl.java

@@ -26,9 +26,6 @@ public class WorkbasketImpl extends WorkbasketSummaryImpl implements Workbasket
 
   @Override
   public void setCustomAttribute(WorkbasketCustomField customField, String value) {
-    if (value == null) {
-      value = "";
-    }
     switch (customField) {
       case CUSTOM_1:
         custom1 = value;

lib/taskana-core/src/main/java/pro/taskana/workbasket/internal/models/WorkbasketSummaryImpl.java

@@ -17,10 +17,10 @@ public class WorkbasketSummaryImpl implements WorkbasketSummary {
   protected String owner;
   protected String domain;
   protected WorkbasketType type;
-  protected String custom1 = "";
+  protected String custom1;
-  protected String custom2 = "";
+  protected String custom2;
-  protected String custom3 = "";
+  protected String custom3;
-  protected String custom4 = "";
+  protected String custom4;
   protected String orgLevel1;
   protected String orgLevel2;
   protected String orgLevel3;
@@ -130,11 +130,7 @@ public class WorkbasketSummaryImpl implements WorkbasketSummary {
   }
 
   public void setCustom1(String custom1) {
-    if (custom1 == null) {
+    this.custom1 = custom1;
-      this.custom1 = "";
-    } else {
-      this.custom1 = custom1;
-    }
   }
 
   public String getCustom2() {
@@ -142,11 +138,7 @@ public class WorkbasketSummaryImpl implements WorkbasketSummary {
   }
 
   public void setCustom2(String custom2) {
-    if (custom2 == null) {
+    this.custom2 = custom2;
-      this.custom2 = "";
-    } else {
-      this.custom2 = custom2;
-    }
   }
 
   public String getCustom3() {
@@ -154,11 +146,7 @@ public class WorkbasketSummaryImpl implements WorkbasketSummary {
   }
 
   public void setCustom3(String custom3) {
-    if (custom3 == null) {
+    this.custom3 = custom3;
-      this.custom3 = "";
-    } else {
-      this.custom3 = custom3;
-    }
   }
 
   public String getCustom4() {
@@ -166,11 +154,7 @@ public class WorkbasketSummaryImpl implements WorkbasketSummary {
   }
 
   public void setCustom4(String custom4) {
-    if (custom4 == null) {
+    this.custom4 = custom4;
-      this.custom4 = "";
-    } else {
-      this.custom4 = custom4;
-    }
   }
 
   @Override

lib/taskana-core/src/test/java/acceptance/classification/CreateClassificationAccTest.java

@@ -4,14 +4,11 @@ import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import acceptance.AbstractAccTest;
-import java.util.Arrays;
-import org.assertj.core.api.SoftAssertions;
 import org.assertj.core.api.ThrowableAssert.ThrowingCallable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestTemplate;
 import org.junit.jupiter.api.extension.ExtendWith;
 
-import pro.taskana.classification.api.ClassificationCustomField;
 import pro.taskana.classification.api.ClassificationService;
 import pro.taskana.classification.api.exceptions.ClassificationAlreadyExistException;
 import pro.taskana.classification.api.exceptions.MalformedServiceLevelException;
@@ -55,48 +52,6 @@ class CreateClassificationAccTest extends AbstractAccTest {
     assertThat(classification.getId()).startsWith(IdGenerator.ID_PREFIX_CLASSIFICATION);
   }
 
-  @WithAccessId(user = "businessadmin")
-  @Test
-  void should_InitializeCustomFieldsToEmptyString_When_ClassificationIsCreated() throws Exception {
-    Classification classification = CLASSIFICATION_SERVICE.newClassification("Key01", "", "TASK");
-    classification.setIsValidInDomain(true);
-    classification.setServiceLevel("P1D");
-    Classification createdClassification =
-        CLASSIFICATION_SERVICE.createClassification(classification);
-
-    SoftAssertions softly = new SoftAssertions();
-    Arrays.stream(ClassificationCustomField.values())
-        .forEach(
-            customField ->
-                softly
-                    .assertThat(createdClassification.getCustomAttribute(customField))
-                    .describedAs("CustomField was null: " + customField)
-                    .isNotNull());
-    softly.assertAll();
-  }
-
-  @WithAccessId(user = "businessadmin")
-  @Test
-  void should_SetCustomFieldToEmptyString_When_SetToNullByUser() throws Exception {
-    Classification classification = CLASSIFICATION_SERVICE.newClassification("Key02", "", "TASK");
-    classification.setIsValidInDomain(true);
-    classification.setServiceLevel("P1D");
-    Arrays.stream(ClassificationCustomField.values())
-        .forEach(customField -> classification.setCustomAttribute(customField, null));
-    Classification createdClassification =
-        CLASSIFICATION_SERVICE.createClassification(classification);
-
-    SoftAssertions softly = new SoftAssertions();
-    Arrays.stream(ClassificationCustomField.values())
-        .forEach(
-            customField ->
-                softly
-                    .assertThat(createdClassification.getCustomAttribute(customField))
-                    .describedAs("CustomField was null: " + customField)
-                    .isNotNull());
-    softly.assertAll();
-  }
-
   @WithAccessId(user = "businessadmin")
   @Test
   void testCreateClassificationWithMasterCopy() throws Exception {

lib/taskana-core/src/test/java/acceptance/classification/UpdateClassificationAccTest.java

@@ -7,9 +7,7 @@ import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import acceptance.AbstractAccTest;
 import java.time.Duration;
 import java.time.Instant;
-import java.util.Arrays;
 import java.util.List;
-import org.assertj.core.api.SoftAssertions;
 import org.assertj.core.api.ThrowableAssert.ThrowingCallable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestTemplate;
@@ -76,26 +74,6 @@ class UpdateClassificationAccTest extends AbstractAccTest {
     assertThat(modifiedBefore).isBefore(updatedClassification.getModified());
   }
 
-  @WithAccessId(user = "businessadmin")
-  @Test
-  void should_SetCustomAttributeToEmptyString_When_SetToNullDuringUpdate() throws Exception {
-    Classification classification = classificationService.getClassification("T2100", "DOMAIN_A");
-    Arrays.stream(ClassificationCustomField.values())
-        .forEach(customField -> classification.setCustomAttribute(customField, null));
-    Classification updatedClassification =
-        classificationService.updateClassification(classification);
-
-    SoftAssertions softly = new SoftAssertions();
-    Arrays.stream(ClassificationCustomField.values())
-        .forEach(
-            customField ->
-                softly
-                    .assertThat(updatedClassification.getCustomAttribute(customField))
-                    .describedAs("CustomField was null: " + customField)
-                    .isNotNull());
-    softly.assertAll();
-  }
-
   @Test
   void should_ThrowException_When_UserIsNotAuthorized() throws Exception {
     Classification classification = classificationService.getClassification("T2100", "DOMAIN_A");

lib/taskana-core/src/test/java/acceptance/task/CreateTaskAccTest.java

@@ -8,7 +8,6 @@ import acceptance.TaskTestMapper;
 import acceptance.TaskanaEngineProxy;
 import java.time.Duration;
 import java.time.Instant;
-import java.util.Arrays;
 import java.util.Map;
 import java.util.Set;
 import java.util.function.Consumer;
@@ -16,7 +15,6 @@ import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 import org.apache.ibatis.session.Configuration;
 import org.apache.ibatis.session.SqlSession;
-import org.assertj.core.api.SoftAssertions;
 import org.assertj.core.api.ThrowableAssert.ThrowingCallable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestTemplate;
@@ -576,52 +574,6 @@ class CreateTaskAccTest extends AbstractAccTest {
     assertThat(createdTask.getName()).isEqualTo("Test Name");
   }
 
-  @WithAccessId(user = "user-1-1")
-  @Test
-  void should_SetCustomFieldToEmptyString_When_SetToNullByUser() throws Exception {
-
-    Task newTask = taskService.newTask("USER-1-1", "DOMAIN_A");
-    newTask.setClassificationKey("T2100");
-    newTask.setPrimaryObjRef(
-        createObjectReference("COMPANY_A", "SYSTEM_A", "INSTANCE_A", "VNR", "1234567"));
-    newTask.setName("Test Name");
-    Arrays.stream(TaskCustomField.values())
-        .forEach(customField -> newTask.setCustomAttribute(customField, null));
-    Task createdTask = taskService.createTask(newTask);
-
-    SoftAssertions softly = new SoftAssertions();
-    Arrays.stream(TaskCustomField.values())
-        .forEach(
-            customField ->
-                softly
-                    .assertThat(createdTask.getCustomAttribute(customField))
-                    .describedAs("CustomField was null: " + customField)
-                    .isNotNull());
-    softly.assertAll();
-  }
-
-  @WithAccessId(user = "user-1-1")
-  @Test
-  void should_InitializeCustomFieldsToEmptyString_When_TaskIsCreated() throws Exception {
-
-    Task newTask = taskService.newTask("USER-1-1", "DOMAIN_A");
-    newTask.setClassificationKey("T2100");
-    newTask.setPrimaryObjRef(
-        createObjectReference("COMPANY_A", "SYSTEM_A", "INSTANCE_A", "VNR", "1234567"));
-    newTask.setName("Test Name");
-    Task createdTask = taskService.createTask(newTask);
-
-    SoftAssertions softly = new SoftAssertions();
-    Arrays.stream(TaskCustomField.values())
-        .forEach(
-            customField ->
-                softly
-                    .assertThat(createdTask.getCustomAttribute(customField))
-                    .describedAs("CustomField was null: " + customField)
-                    .isNotNull());
-    softly.assertAll();
-  }
-
   @WithAccessId(user = "user-1-1")
   @Test
   void testUseClassificationMetadataFromCorrectDomainForNewTask() throws Exception {

lib/taskana-core/src/test/java/acceptance/task/QueryTasksAccTest.java

@@ -343,6 +343,102 @@ class QueryTasksAccTest extends AbstractAccTest {
       assertThat(results).isEqualTo(expectedCount);
     }
 
+    @WithAccessId(user = "admin")
+    @Test
+    void should_ReturnTasksWithEmptyCustomField_When_QueriedByCustomFieldWhichIsNull()
+        throws InvalidArgumentException {
+      List<TaskSummary> results =
+          taskService
+              .createTaskQuery()
+              .customAttributeIn(TaskCustomField.CUSTOM_9, new String[] {null})
+              .list();
+      assertThat(results).hasSize(1);
+
+      results =
+          taskService
+              .createTaskQuery()
+              .customAttributeIn(TaskCustomField.CUSTOM_9, null, "custom9")
+              .list();
+      assertThat(results).hasSize(2);
+
+      results =
+          taskService
+              .createTaskQuery()
+              .customAttributeIn(TaskCustomField.CUSTOM_9, new String[] {null})
+              .customAttributeIn(TaskCustomField.CUSTOM_14, "abc")
+              .list();
+      assertThat(results).hasSize(1);
+    }
+
+    @WithAccessId(user = "admin")
+    @Test
+    void should_ReturnTasksWithNullCustomField_When_QueriedByCustomFieldWhichIsEmpty()
+        throws InvalidArgumentException {
+      List<TaskSummary> results =
+          taskService.createTaskQuery().customAttributeIn(TaskCustomField.CUSTOM_9, "").list();
+      assertThat(results).hasSize(86);
+    }
+
+    @WithAccessId(user = "admin")
+    @Test
+    void should_AllowToQueryTasksByCustomFieldWithNullAndEmptyInParallel()
+        throws InvalidArgumentException {
+      List<TaskSummary> results =
+          taskService
+              .createTaskQuery()
+              .customAttributeIn(TaskCustomField.CUSTOM_9, "", null)
+              .list();
+      assertThat(results).hasSize(87);
+    }
+
+    @WithAccessId(user = "admin")
+    @Test
+    void should_ReturnTasksWithEmptyCustomField_When_QueriedByCustomFieldWhichIsNotNull()
+        throws InvalidArgumentException {
+      List<TaskSummary> results =
+          taskService
+              .createTaskQuery()
+              .customAttributeNotIn(TaskCustomField.CUSTOM_9, new String[] {null})
+              .list();
+      assertThat(results).hasSize(87);
+
+      results =
+          taskService
+              .createTaskQuery()
+              .customAttributeNotIn(TaskCustomField.CUSTOM_9, null, "custom9")
+              .list();
+      assertThat(results).hasSize(86);
+
+      results =
+          taskService
+              .createTaskQuery()
+              .customAttributeNotIn(TaskCustomField.CUSTOM_9, new String[] {null})
+              .customAttributeNotIn(TaskCustomField.CUSTOM_10, "custom10")
+              .list();
+      assertThat(results).hasSize(86);
+    }
+
+    @WithAccessId(user = "admin")
+    @Test
+    void should_ReturnTasksWithNullCustomField_When_QueriedByCustomFieldWhichIsNotEmpty()
+        throws InvalidArgumentException {
+      List<TaskSummary> results =
+          taskService.createTaskQuery().customAttributeNotIn(TaskCustomField.CUSTOM_9, "").list();
+      assertThat(results).hasSize(2);
+    }
+
+    @WithAccessId(user = "admin")
+    @Test
+    void should_AllowToQueryTasksByCustomFieldWithNeitherNullOrEmptyInParallel()
+        throws InvalidArgumentException {
+      List<TaskSummary> results =
+          taskService
+              .createTaskQuery()
+              .customAttributeNotIn(TaskCustomField.CUSTOM_9, "", null)
+              .list();
+      assertThat(results).hasSize(1);
+    }
+
     @WithAccessId(user = "admin")
     @Test
     void should_ThrowException_When_SearchArgumentInLikeQueryIsNotGiven() {

lib/taskana-core/src/test/java/acceptance/task/UpdateTaskAccTest.java

@@ -15,11 +15,9 @@ import static pro.taskana.task.api.TaskCustomField.CUSTOM_7;
 
 import acceptance.AbstractAccTest;
 import java.time.Instant;
-import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import org.assertj.core.api.SoftAssertions;
 import org.assertj.core.api.ThrowableAssert.ThrowingCallable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestTemplate;
@@ -245,25 +243,6 @@ class UpdateTaskAccTest extends AbstractAccTest {
     assertThat(updatedTask).isNotNull();
   }
 
-  @WithAccessId(user = "user-1-1")
-  @Test
-  void should_SetCustomAttributeToEmptyString_When_SetToNullDuringUpdate() throws Exception {
-    Task task = taskService.getTask("TKI:000000000000000000000000000000000000");
-    Arrays.stream(TaskCustomField.values())
-        .forEach(customField -> task.setCustomAttribute(customField, null));
-    Task updatedTask = taskService.updateTask(task);
-
-    SoftAssertions softly = new SoftAssertions();
-    Arrays.stream(TaskCustomField.values())
-        .forEach(
-            customField ->
-                softly
-                    .assertThat(updatedTask.getCustomAttribute(customField))
-                    .describedAs("CustomField was null: " + customField)
-                    .isNotNull());
-    softly.assertAll();
-  }
-
   @WithAccessId(user = "user-1-1")
   @Test
   void should_ThrowException_When_ModificationOfWorkbasketKeyIsAttempted() throws Exception {
@@ -317,7 +296,7 @@ class UpdateTaskAccTest extends AbstractAccTest {
       assertThat(task.getCustomAttribute(CUSTOM_3)).isEqualTo("This is modifiedValue 3");
       assertThat(task.getCustomAttribute(CUSTOM_7)).isEqualTo("This is modifiedValue 7");
       assertThat(task.getCustomAttribute(CUSTOM_16)).isEqualTo("This is modifiedValue 16");
-      assertThat(task.getCustomAttribute(CUSTOM_14)).isEmpty();
+      assertThat(task.getCustomAttribute(CUSTOM_14)).isNull();
     }
   }
 
@@ -345,7 +324,7 @@ class UpdateTaskAccTest extends AbstractAccTest {
       assertThat(task.getCustomAttribute(CUSTOM_10)).isEqualTo("This is modifiedValue 10");
       assertThat(task.getCustomAttribute(CUSTOM_12)).isEqualTo("This is modifiedValue 12");
       assertThat(task.getCustomAttribute(CUSTOM_2)).isNotNull();
-      assertThat(task.getCustomAttribute(CUSTOM_16)).isEmpty();
+      assertThat(task.getCustomAttribute(CUSTOM_16)).isNull();
     }
   }
 

lib/taskana-core/src/test/java/acceptance/workbasket/CreateWorkbasketAccTest.java

@@ -4,9 +4,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 
 import acceptance.AbstractAccTest;
-import java.util.Arrays;
 import java.util.List;
-import org.assertj.core.api.SoftAssertions;
 import org.assertj.core.api.ThrowableAssert.ThrowingCallable;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestTemplate;
@@ -17,7 +15,6 @@ import pro.taskana.common.api.exceptions.InvalidArgumentException;
 import pro.taskana.common.api.exceptions.NotAuthorizedException;
 import pro.taskana.common.test.security.JaasExtension;
 import pro.taskana.common.test.security.WithAccessId;
-import pro.taskana.workbasket.api.WorkbasketCustomField;
 import pro.taskana.workbasket.api.WorkbasketPermission;
 import pro.taskana.workbasket.api.WorkbasketService;
 import pro.taskana.workbasket.api.WorkbasketType;
@@ -102,56 +99,6 @@ class CreateWorkbasketAccTest extends AbstractAccTest {
     assertThatThrownBy(call).isInstanceOf(DomainNotFoundException.class);
   }
 
-  @WithAccessId(user = "businessadmin")
-  @Test
-  void should_InitializeCustomFieldsToEmptyString_When_WorkbasketIsCreated()
-      throws InvalidArgumentException, WorkbasketAlreadyExistException, DomainNotFoundException,
-          NotAuthorizedException {
-    WorkbasketService workbasketService = taskanaEngine.getWorkbasketService();
-
-    Workbasket workbasket = workbasketService.newWorkbasket("GPK_NULL1", "DOMAIN_A");
-    workbasket.setName("Megabasket");
-    workbasket.setType(WorkbasketType.GROUP);
-    workbasket.setOrgLevel1("company");
-    Workbasket createdWorkbasket = workbasketService.createWorkbasket(workbasket);
-
-    SoftAssertions softly = new SoftAssertions();
-    Arrays.stream(WorkbasketCustomField.values())
-        .forEach(
-            customField ->
-                softly
-                    .assertThat(createdWorkbasket.getCustomAttribute(customField))
-                    .describedAs("CustomField was null: " + customField)
-                    .isNotNull());
-    softly.assertAll();
-  }
-
-  @WithAccessId(user = "businessadmin")
-  @Test
-  void should_SetCustomFieldToEmptyString_When_SetToNullByUser()
-      throws InvalidArgumentException, WorkbasketAlreadyExistException, DomainNotFoundException,
-          NotAuthorizedException {
-    WorkbasketService workbasketService = taskanaEngine.getWorkbasketService();
-
-    Workbasket workbasket = workbasketService.newWorkbasket("GPK_NULL2", "DOMAIN_A");
-    workbasket.setName("Megabasket");
-    workbasket.setType(WorkbasketType.GROUP);
-    workbasket.setOrgLevel1("company");
-    Arrays.stream(WorkbasketCustomField.values())
-        .forEach(customField -> workbasket.setCustomAttribute(customField, null));
-    Workbasket createdWorkbasket = workbasketService.createWorkbasket(workbasket);
-
-    SoftAssertions softly = new SoftAssertions();
-    Arrays.stream(WorkbasketCustomField.values())
-        .forEach(
-            customField ->
-                softly
-                    .assertThat(createdWorkbasket.getCustomAttribute(customField))
-                    .describedAs("CustomField was null: " + customField)
-                    .isNotNull());
-    softly.assertAll();
-  }
-
   @WithAccessId(user = "businessadmin")
   @Test
   void testCreateWorkbasketWithMissingRequiredField() {

lib/taskana-core/src/test/java/acceptance/workbasket/UpdateWorkbasketAccTest.java

@@ -7,8 +7,6 @@ import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import acceptance.AbstractAccTest;
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
-import java.util.Arrays;
-import org.assertj.core.api.SoftAssertions;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.TestTemplate;
 import org.junit.jupiter.api.extension.ExtendWith;
@@ -60,28 +58,6 @@ class UpdateWorkbasketAccTest extends AbstractAccTest {
     assertThat(updatedWorkbasket.getModified()).isNotEqualTo(modified);
   }
 
-  @WithAccessId(user = "businessadmin")
-  @Test
-  void should_SetCustomAttributeToEmptyString_When_SetToNullDuringUpdate() throws Exception {
-    WorkbasketService workbasketService = taskanaEngine.getWorkbasketService();
-    Workbasket workbasket = workbasketService.getWorkbasket("GPK_KSC", "DOMAIN_A");
-    Arrays.stream(WorkbasketCustomField.values())
-        .forEach(customField -> workbasket.setCustomAttribute(customField, null));
-    workbasketService.updateWorkbasket(workbasket);
-
-    Workbasket updatedWorkbasket = workbasketService.getWorkbasket("GPK_KSC", "DOMAIN_A");
-
-    SoftAssertions softly = new SoftAssertions();
-    Arrays.stream(WorkbasketCustomField.values())
-        .forEach(
-            customField ->
-                softly
-                    .assertThat(updatedWorkbasket.getCustomAttribute(customField))
-                    .describedAs("CustomField was null: " + customField)
-                    .isNotNull());
-    softly.assertAll();
-  }
-
   @WithAccessId(user = "businessadmin")
   @Test
   void should_ThrowException_When_UpdatingWorkbasketWithInvalidName() throws Exception {

rest/taskana-rest-spring/src/main/java/pro/taskana/monitor/rest/MonitorController.java

@@ -21,6 +21,7 @@ import pro.taskana.monitor.api.TaskTimestamp;
 import pro.taskana.monitor.api.reports.ClassificationCategoryReport;
 import pro.taskana.monitor.api.reports.ClassificationReport;
 import pro.taskana.monitor.api.reports.TaskCustomFieldValueReport;
+import pro.taskana.monitor.api.reports.TaskStatusReport;
 import pro.taskana.monitor.api.reports.TimestampReport;
 import pro.taskana.monitor.api.reports.WorkbasketPriorityReport;
 import pro.taskana.monitor.api.reports.WorkbasketReport;
@@ -298,19 +299,23 @@ public class MonitorController {
       @RequestParam(name = "priority-minimum", required = false) Integer priorityMinimum)
       throws NotAuthorizedException {
 
+    TaskStatusReport.Builder builder = monitorService.createTaskStatusReportBuilder();
+    if (states != null && !states.isEmpty()) {
+      builder = builder.stateIn(states);
+    }
+    if (domains != null && !domains.isEmpty()) {
+      builder.domainIn(domains);
+    }
+    if (workbasketIds != null && !workbasketIds.isEmpty()) {
+      builder.workbasketIdsIn(workbasketIds);
+    }
+    if (priorityMinimum != null) {
+      builder.priorityMinimum(priorityMinimum);
+    }
+
     return ResponseEntity.ok(
         reportRepresentationModelAssembler.toModel(
-            monitorService
+            builder.buildReport(), domains, states, workbasketIds, priorityMinimum));
-                .createTaskStatusReportBuilder()
-                .stateIn(states)
-                .domainIn(domains)
-                .workbasketIdsIn(workbasketIds)
-                .priorityMinimum(priorityMinimum)
-                .buildReport(),
-            domains,
-            states,
-            workbasketIds,
-            priorityMinimum));
   }
 
   /**