mapstruct · filiphr · Nov 13, 2022 · Oct 27, 2022 · Nov 12, 2022
diff --git a/documentation/src/main/asciidoc/chapter-2-set-up.asciidoc b/documentation/src/main/asciidoc/chapter-2-set-up.asciidoc
@@ -266,6 +266,30 @@ If a policy is given for a specific bean mapping via `@BeanMapping#ignoreUnmappe
 disableBuilders`
 |If set to `true`, then MapStruct will not use builder patterns when doing the mapping. This is equivalent to doing `@Mapper( builder = @Builder( disableBuilder = true ) )` for all of your mappers.
 |`false`
+
+|`mapstruct.nullValueIterableMappingStrategy`
+|The strategy to be applied when `null` is passed as a source value to an iterable mapping.
+
+Supported values are:
+
+* `RETURN_NULL`: if `null` is passed as a source value, then `null` will be returned
+* `RETURN_DEFAULT`: if `null` is passed then a default value (empty collection) will be returned
+
+If a strategy is given for a specific mapper via `@Mapper#nullValueIterableMappingStrategy()`, the value from the annotation takes precedence.
+If a strategy is given for a specific iterable mapping via `@IterableMapping#nullValueMappingStrategy()`, it takes precedence over both `@Mapper#nullValueIterableMappingStrategy()` and the option.
+|`RETURN_NULL`
+
+|`mapstruct.nullValueMapMappingStrategy`
+|The strategy to be applied when `null` is passed as a source value to a map mapping.
+
+Supported values are:
+
+* `RETURN_NULL`: if `null` is passed as a source value, then `null` will be returned
+* `RETURN_DEFAULT`: if `null` is passed then a default value (empty map) will be returned
+
+If a strategy is given for a specific mapper via `@Mapper#nullValueMapMappingStrategy()`, the value from the annotation takes precedence.
+If a strategy is given for a specific map mapping via `@MapMapping#nullValueMappingStrategy()`, it takes precedence over both `@Mapper#nullValueMapMappingStrategy()` and the option.
+|`RETURN_NULL`
 |===
 
 === Using MapStruct with the Java Module System

diff --git a/processor/src/main/java/org/mapstruct/ap/MappingProcessor.java b/processor/src/main/java/org/mapstruct/ap/MappingProcessor.java
@@ -12,6 +12,7 @@
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.ServiceLoader;
 import java.util.Set;
@@ -32,6 +33,7 @@
 import javax.lang.model.util.ElementKindVisitor6;
 import javax.tools.Diagnostic.Kind;
 
+import org.mapstruct.ap.internal.gem.NullValueMappingStrategyGem;
 import org.mapstruct.ap.internal.model.Mapper;
 import org.mapstruct.ap.internal.option.Options;
 import org.mapstruct.ap.internal.gem.MapperGem;
@@ -87,7 +89,9 @@
     MappingProcessor.DEFAULT_COMPONENT_MODEL,
     MappingProcessor.DEFAULT_INJECTION_STRATEGY,
     MappingProcessor.DISABLE_BUILDERS,
-    MappingProcessor.VERBOSE
+    MappingProcessor.VERBOSE,
+    MappingProcessor.NULL_VALUE_ITERABLE_MAPPING_STRATEGY,
+    MappingProcessor.NULL_VALUE_MAP_MAPPING_STRATEGY,
 })
 public class MappingProcessor extends AbstractProcessor {
 
@@ -106,6 +110,8 @@ public class MappingProcessor extends AbstractProcessor {
     protected static final String ALWAYS_GENERATE_SERVICE_FILE = "mapstruct.alwaysGenerateServicesFile";
     protected static final String DISABLE_BUILDERS = "mapstruct.disableBuilders";
     protected static final String VERBOSE = "mapstruct.verbose";
+    protected static final String NULL_VALUE_ITERABLE_MAPPING_STRATEGY = "mapstruct.nullValueIterableMappingStrategy";
+    protected static final String NULL_VALUE_MAP_MAPPING_STRATEGY = "mapstruct.nullValueMapMappingStrategy";
 
     private Options options;
 
@@ -139,6 +145,9 @@ public synchronized void init(ProcessingEnvironment processingEnv) {
     private Options createOptions() {
         String unmappedTargetPolicy = processingEnv.getOptions().get( UNMAPPED_TARGET_POLICY );
         String unmappedSourcePolicy = processingEnv.getOptions().get( UNMAPPED_SOURCE_POLICY );
+        String nullValueIterableMappingStrategy = processingEnv.getOptions()
+            .get( NULL_VALUE_ITERABLE_MAPPING_STRATEGY );
+        String nullValueMapMappingStrategy = processingEnv.getOptions().get( NULL_VALUE_MAP_MAPPING_STRATEGY );
 
         return new Options(
             Boolean.parseBoolean( processingEnv.getOptions().get( SUPPRESS_GENERATOR_TIMESTAMP ) ),
@@ -149,7 +158,12 @@ private Options createOptions() {
             processingEnv.getOptions().get( DEFAULT_INJECTION_STRATEGY ),
             Boolean.parseBoolean( processingEnv.getOptions().get( ALWAYS_GENERATE_SERVICE_FILE ) ),
             Boolean.parseBoolean( processingEnv.getOptions().get( DISABLE_BUILDERS ) ),
-            Boolean.parseBoolean( processingEnv.getOptions().get( VERBOSE ) )
+            Boolean.parseBoolean( processingEnv.getOptions().get( VERBOSE ) ),
+            nullValueIterableMappingStrategy != null ?
+                NullValueMappingStrategyGem.valueOf( nullValueIterableMappingStrategy.toUpperCase( Locale.ROOT ) ) :
+                null,
+            nullValueMapMappingStrategy != null ?
+                NullValueMappingStrategyGem.valueOf( nullValueMapMappingStrategy.toUpperCase( Locale.ROOT ) ) : null
         );
     }
 

diff --git a/processor/src/main/java/org/mapstruct/ap/internal/model/source/DefaultOptions.java b/processor/src/main/java/org/mapstruct/ap/internal/model/source/DefaultOptions.java
@@ -132,10 +132,18 @@ public SubclassExhaustiveStrategyGem getSubclassExhaustiveStrategy() {
     }
 
     public NullValueMappingStrategyGem getNullValueIterableMappingStrategy() {
+        NullValueMappingStrategyGem nullValueIterableMappingStrategy = options.getNullValueIterableMappingStrategy();
+        if ( nullValueIterableMappingStrategy != null ) {
+            return nullValueIterableMappingStrategy;
+        }
         return NullValueMappingStrategyGem.valueOf( mapper.nullValueIterableMappingStrategy().getDefaultValue() );
     }
 
     public NullValueMappingStrategyGem getNullValueMapMappingStrategy() {
+        NullValueMappingStrategyGem nullValueMapMappingStrategy = options.getNullValueMapMappingStrategy();
+        if ( nullValueMapMappingStrategy != null ) {
+            return nullValueMapMappingStrategy;
+        }
         return NullValueMappingStrategyGem.valueOf( mapper.nullValueMapMappingStrategy().getDefaultValue() );
     }
 

diff --git a/processor/src/main/java/org/mapstruct/ap/internal/option/Options.java b/processor/src/main/java/org/mapstruct/ap/internal/option/Options.java
@@ -5,6 +5,7 @@
  */
 package org.mapstruct.ap.internal.option;
 
+import org.mapstruct.ap.internal.gem.NullValueMappingStrategyGem;
 import org.mapstruct.ap.internal.gem.ReportingPolicyGem;
 
 /**
@@ -23,14 +24,21 @@ public class Options {
     private final String defaultInjectionStrategy;
     private final boolean disableBuilders;
     private final boolean verbose;
+    private final NullValueMappingStrategyGem nullValueIterableMappingStrategy;
+    private final NullValueMappingStrategyGem nullValueMapMappingStrategy;
 
+    //CHECKSTYLE:OFF
     public Options(boolean suppressGeneratorTimestamp, boolean suppressGeneratorVersionComment,
                    ReportingPolicyGem unmappedTargetPolicy,
                    ReportingPolicyGem unmappedSourcePolicy,
                    String defaultComponentModel, String defaultInjectionStrategy,
                    boolean alwaysGenerateSpi,
                    boolean disableBuilders,
-                   boolean verbose) {
+                   boolean verbose,
+                   NullValueMappingStrategyGem nullValueIterableMappingStrategy,
+                   NullValueMappingStrategyGem nullValueMapMappingStrategy
+                   ) {
+        //CHECKSTYLE:ON
         this.suppressGeneratorTimestamp = suppressGeneratorTimestamp;
         this.suppressGeneratorVersionComment = suppressGeneratorVersionComment;
         this.unmappedTargetPolicy = unmappedTargetPolicy;
@@ -40,6 +48,8 @@ public Options(boolean suppressGeneratorTimestamp, boolean suppressGeneratorVers
         this.alwaysGenerateSpi = alwaysGenerateSpi;
         this.disableBuilders = disableBuilders;
         this.verbose = verbose;
+        this.nullValueIterableMappingStrategy = nullValueIterableMappingStrategy;
+        this.nullValueMapMappingStrategy = nullValueMapMappingStrategy;
     }
 
     public boolean isSuppressGeneratorTimestamp() {
@@ -77,4 +87,12 @@ public boolean isDisableBuilders() {
     public boolean isVerbose() {
         return verbose;
     }
+
+    public NullValueMappingStrategyGem getNullValueIterableMappingStrategy() {
+        return nullValueIterableMappingStrategy;
+    }
+
+    public NullValueMappingStrategyGem getNullValueMapMappingStrategy() {
+        return nullValueMapMappingStrategy;
+    }
 }
diff --git a/processor/src/test/java/org/mapstruct/ap/test/nullvaluemapping/CarListMapper.java b/processor/src/test/java/org/mapstruct/ap/test/nullvaluemapping/CarListMapper.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.nullvaluemapping;
+
+import java.util.List;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+import org.mapstruct.ap.test.nullvaluemapping._target.CarDto;
+import org.mapstruct.ap.test.nullvaluemapping.source.Car;
+import org.mapstruct.factory.Mappers;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper
+public interface CarListMapper {
+
+    CarListMapper INSTANCE = Mappers.getMapper( CarListMapper.class );
+
+    @Mapping(target = "seatCount", ignore = true)
+    @Mapping(target = "model", ignore = true)
+    @Mapping(target = "catalogId", ignore = true)
+    CarDto map(Car car);
+
+    List<CarDto> carsToCarDtoList(List<Car> cars);
+}
diff --git a/...or/src/test/java/org/mapstruct/ap/test/nullvaluemapping/CarListMapperSettingOnMapper.java b/...or/src/test/java/org/mapstruct/ap/test/nullvaluemapping/CarListMapperSettingOnMapper.java
@@ -0,0 +1,31 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.nullvaluemapping;
+
+import java.util.List;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+import org.mapstruct.NullValueMappingStrategy;
+import org.mapstruct.ap.test.nullvaluemapping._target.CarDto;
+import org.mapstruct.ap.test.nullvaluemapping.source.Car;
+import org.mapstruct.factory.Mappers;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper(nullValueIterableMappingStrategy = NullValueMappingStrategy.RETURN_NULL)
+public interface CarListMapperSettingOnMapper {
+
+    CarListMapperSettingOnMapper INSTANCE = Mappers.getMapper( CarListMapperSettingOnMapper.class );
+
+    @Mapping(target = "seatCount", ignore = true)
+    @Mapping(target = "model", ignore = true)
+    @Mapping(target = "catalogId", ignore = true)
+    CarDto map(Car car);
+
+    List<CarDto> carsToCarDtoList(List<Car> cars);
+}
diff --git a/processor/src/test/java/org/mapstruct/ap/test/nullvaluemapping/CarMapMapper.java b/processor/src/test/java/org/mapstruct/ap/test/nullvaluemapping/CarMapMapper.java
@@ -0,0 +1,30 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.nullvaluemapping;
+
+import java.util.Map;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+import org.mapstruct.ap.test.nullvaluemapping._target.CarDto;
+import org.mapstruct.ap.test.nullvaluemapping.source.Car;
+import org.mapstruct.factory.Mappers;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper
+public interface CarMapMapper {
+
+    CarMapMapper INSTANCE = Mappers.getMapper( CarMapMapper.class );
+
+    @Mapping(target = "seatCount", ignore = true)
+    @Mapping(target = "model", ignore = true)
+    @Mapping(target = "catalogId", ignore = true)
+    CarDto map(Car car);
+
+    Map<Integer, CarDto> carsToCarDtoMap(Map<Integer, Car> cars);
+}
diff --git a/...sor/src/test/java/org/mapstruct/ap/test/nullvaluemapping/CarMapMapperSettingOnMapper.java b/...sor/src/test/java/org/mapstruct/ap/test/nullvaluemapping/CarMapMapperSettingOnMapper.java
@@ -0,0 +1,31 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.nullvaluemapping;
+
+import java.util.Map;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+import org.mapstruct.NullValueMappingStrategy;
+import org.mapstruct.ap.test.nullvaluemapping._target.CarDto;
+import org.mapstruct.ap.test.nullvaluemapping.source.Car;
+import org.mapstruct.factory.Mappers;
+
+/**
+ * @author Filip Hrisafov
+ */
+@Mapper(nullValueMapMappingStrategy = NullValueMappingStrategy.RETURN_NULL)
+public interface CarMapMapperSettingOnMapper {
+
+    CarMapMapperSettingOnMapper INSTANCE = Mappers.getMapper( CarMapMapperSettingOnMapper.class );
+
+    @Mapping(target = "seatCount", ignore = true)
+    @Mapping(target = "model", ignore = true)
+    @Mapping(target = "catalogId", ignore = true)
+    CarDto map(Car car);
+
+    Map<Integer, CarDto> carsToCarDtoMap(Map<Integer, Car> cars);
+}
diff --git a/...est/java/org/mapstruct/ap/test/nullvaluemapping/NullValueIterableMappingStrategyTest.java b/...est/java/org/mapstruct/ap/test/nullvaluemapping/NullValueIterableMappingStrategyTest.java
@@ -0,0 +1,45 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.nullvaluemapping;
+
+import org.mapstruct.ap.test.nullvaluemapping._target.CarDto;
+import org.mapstruct.ap.test.nullvaluemapping.source.Car;
+import org.mapstruct.ap.testutil.IssueKey;
+import org.mapstruct.ap.testutil.ProcessorTest;
+import org.mapstruct.ap.testutil.WithClasses;
+import org.mapstruct.ap.testutil.compilation.annotation.ProcessorOption;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Filip Hrisafov
+ */
+@WithClasses({
+    CarDto.class,
+    Car.class
+})
+@IssueKey("2953")
+public class NullValueIterableMappingStrategyTest {
+
+    @ProcessorTest
+    @ProcessorOption(name = "mapstruct.nullValueIterableMappingStrategy", value = "return_default")
+    @WithClasses({
+        CarListMapper.class
+    })
+    void globalNullIterableMappingStrategy() {
+        assertThat( CarListMapper.INSTANCE.carsToCarDtoList( null ) ).isEmpty();
+    }
+
+    @ProcessorTest
+    @ProcessorOption(name = "mapstruct.nullValueIterableMappingStrategy", value = "return_default")
+    @WithClasses({
+        CarListMapperSettingOnMapper.class
+    })
+    void globalNullMapMappingStrategyWithOverrideInMapper() {
+        // Explicit definition in @Mapper should override global
+        assertThat( CarListMapperSettingOnMapper.INSTANCE.carsToCarDtoList( null ) ).isNull();
+    }
+}
diff --git a/...src/test/java/org/mapstruct/ap/test/nullvaluemapping/NullValueMapMappingStrategyTest.java b/...src/test/java/org/mapstruct/ap/test/nullvaluemapping/NullValueMapMappingStrategyTest.java
@@ -0,0 +1,45 @@
+/*
+ * Copyright MapStruct Authors.
+ *
+ * Licensed under the Apache License version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0
+ */
+package org.mapstruct.ap.test.nullvaluemapping;
+
+import org.mapstruct.ap.test.nullvaluemapping._target.CarDto;
+import org.mapstruct.ap.test.nullvaluemapping.source.Car;
+import org.mapstruct.ap.testutil.IssueKey;
+import org.mapstruct.ap.testutil.ProcessorTest;
+import org.mapstruct.ap.testutil.WithClasses;
+import org.mapstruct.ap.testutil.compilation.annotation.ProcessorOption;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Filip Hrisafov
+ */
+@WithClasses({
+    CarDto.class,
+    Car.class
+})
+@IssueKey("2953")
+public class NullValueMapMappingStrategyTest {
+
+    @ProcessorTest
+    @ProcessorOption(name = "mapstruct.nullValueMapMappingStrategy", value = "return_default")
+    @WithClasses({
+        CarMapMapper.class
+    })
+    void globalNullMapMappingStrategy() {
+        assertThat( CarMapMapper.INSTANCE.carsToCarDtoMap( null ) ).isEmpty();
+    }
+
+    @ProcessorTest
+    @ProcessorOption(name = "mapstruct.nullValueMapMappingStrategy", value = "return_default")
+    @WithClasses({
+        CarMapMapperSettingOnMapper.class
+    })
+    void globalNullMapMappingStrategyWithOverrideInMapper() {
+        // Explicit definition in @Mapper should override global
+        assertThat( CarMapMapperSettingOnMapper.INSTANCE.carsToCarDtoMap( null ) ).isNull();
+    }
+}