#187 introducing constant mapping

core/src/main/java/org/mapstruct/Mapping.java

@@ -35,12 +35,15 @@ import java.util.Date;
 public @interface Mapping {
 
     /**
-     * The source name of the configured property as defined by the JavaBeans specification. If used to map an enum
-     * constant, the name of the constant member is to be given.
+     * The source to use for this Mapping. This can either be:
+     * <ol>
+     * <li>The source name of the configured property as defined by the JavaBeans specification.</li>
+     * <li>When used to map an enum constant, the name of the constant member is to be given<./li>.
+     * </ol>
      *
-     * @return The source name of the configured property or enum constant
+     * @return The source name of the configured property or enum constant.
      */
-    String source();
+    String source() default "";
 
     /**
      * The target name of the configured property as defined by the JavaBeans specification. Defaults to the source name
@@ -57,4 +60,12 @@ public @interface Mapping {
      * @return A date format string as processable by {@link SimpleDateFormat}.
      */
     String dateFormat() default "";
+
+    /**
+     * {@link String} expression that uses available mappings and conversion to set the designated target property to
+     * the provided expression.
+     *
+     * @return expression
+     */
+    String expression() default "";
 }

processor/src/main/java/org/mapstruct/ap/model/BeanMappingMethod.java

@@ -38,6 +38,10 @@ import org.mapstruct.ap.model.source.SourceMethod;
 public class BeanMappingMethod extends MappingMethod {
 
     private final List<PropertyMapping> propertyMappings;
+    private final Map<String, List<PropertyMapping>> mappingsByParameter;
+    private final List<PropertyMapping> constantMappings;
+
+
     private final FactoryMethod factoryMethod;
 
     public BeanMappingMethod(SourceMethod method,
@@ -45,6 +49,22 @@ public class BeanMappingMethod extends MappingMethod {
                              FactoryMethod factoryMethod) {
         super( method );
         this.propertyMappings = propertyMappings;
+
+
+        // intialize constant mappings as all mappings, but take out the ones that can be contributed to a
+        // parameter mapping.
+        this.mappingsByParameter = new HashMap<String, List<PropertyMapping>>();
+        this.constantMappings = new ArrayList<PropertyMapping>( propertyMappings );
+        for ( Parameter sourceParameter : getSourceParameters() ) {
+            ArrayList<PropertyMapping> mappingsOfParameter = new ArrayList<PropertyMapping>();
+            mappingsByParameter.put( sourceParameter.getName(), mappingsOfParameter );
+            for ( PropertyMapping mapping : propertyMappings ) {
+                if ( sourceParameter.getName().equals( mapping.getSourceBeanName() ) ) {
+                    mappingsOfParameter.add( mapping );
+                    constantMappings.remove( mapping );
+                }
+            }
+        }
         this.factoryMethod = factoryMethod;
     }
 
@@ -52,18 +72,11 @@ public class BeanMappingMethod extends MappingMethod {
         return propertyMappings;
     }
 
-    public Map<String, List<PropertyMapping>> getPropertyMappingsByParameter() {
-        Map<String, List<PropertyMapping>> mappingsByParameter = new HashMap<String, List<PropertyMapping>>();
+    public List<PropertyMapping> getConstantMappings() {
+        return constantMappings;
+    }
 
-        for ( Parameter sourceParameter : getSourceParameters() ) {
-            ArrayList<PropertyMapping> mappingsOfParameter = new ArrayList<PropertyMapping>();
-            mappingsByParameter.put( sourceParameter.getName(), mappingsOfParameter );
-            for ( PropertyMapping mapping : propertyMappings ) {
-                if ( mapping.getSourceBeanName().equals( sourceParameter.getName() ) ) {
-                    mappingsOfParameter.add( mapping );
-                }
-            }
-        }
+    public Map<String, List<PropertyMapping>> getPropertyMappingsByParameter() {
         return mappingsByParameter;
     }
 

processor/src/main/java/org/mapstruct/ap/model/source/Mapping.java

@@ -22,9 +22,11 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import javax.annotation.processing.Messager;
 import javax.lang.model.element.AnnotationMirror;
 import javax.lang.model.element.AnnotationValue;
 import javax.lang.model.element.Element;
+import javax.tools.Diagnostic;
 
 import org.mapstruct.ap.prism.MappingPrism;
 import org.mapstruct.ap.prism.MappingsPrism;
@@ -40,42 +42,63 @@ public class Mapping {
     private final String sourceName;
     private final String sourceParameterName;
     private final String sourcePropertyName;
+    private final String expression;
     private final String targetName;
     private final String dateFormat;
     private final AnnotationMirror mirror;
     private final AnnotationValue sourceAnnotationValue;
     private final AnnotationValue targetAnnotationValue;
 
-    public static Map<String, List<Mapping>> fromMappingsPrism(MappingsPrism mappingsAnnotation, Element element) {
+    public static Map<String, List<Mapping>> fromMappingsPrism(MappingsPrism mappingsAnnotation, Element element,
+            Messager messager) {
         Map<String, List<Mapping>> mappings = new HashMap<String, List<Mapping>>();
 
-        for ( MappingPrism mapping : mappingsAnnotation.value() ) {
-            if ( !mappings.containsKey( mapping.source() ) ) {
-                mappings.put( mapping.source(), new ArrayList<Mapping>() );
+        for ( MappingPrism mappingPrism : mappingsAnnotation.value() ) {
+            if ( !mappings.containsKey( mappingPrism.source() ) ) {
+                mappings.put( mappingPrism.source(), new ArrayList<Mapping>() );
+            }
+            Mapping mapping = fromMappingPrism( mappingPrism, element, messager );
+            if ( mapping != null ) {
+                mappings.get( mappingPrism.source() ).add( mapping );
             }
-            mappings.get( mapping.source() ).add( fromMappingPrism( mapping, element ) );
         }
 
         return mappings;
     }
 
-    public static Mapping fromMappingPrism(MappingPrism mapping, Element element) {
+    public static Mapping fromMappingPrism(MappingPrism mappingPrism, Element element, Messager messager) {
         String[] sourceNameParts = getSourceNameParts(
-            mapping.source(),
+            mappingPrism.source(),
             element,
-            mapping.mirror,
-            mapping.values.source()
+            mappingPrism.mirror,
+            mappingPrism.values.source()
         );
 
+        if ( mappingPrism.source().isEmpty() && mappingPrism.expression().isEmpty() ) {
+            messager.printMessage( Diagnostic.Kind.ERROR,
+                    "Either define a source or an expression in a Mapping",
+                    element
+            );
+            return null;
+        }
+        else if  ( !mappingPrism.source().isEmpty() && !mappingPrism.expression().isEmpty() ) {
+            messager.printMessage( Diagnostic.Kind.ERROR,
+                    "Source and expression are both defined in Mapping, either define a source or an expression",
+                    element
+            );
+            return null;
+        }
+
         return new Mapping(
-            mapping.source(),
+            mappingPrism.source(),
             sourceNameParts != null ? sourceNameParts[0] : null,
-            sourceNameParts != null ? sourceNameParts[1] : mapping.source(),
-            mapping.target(),
-            mapping.dateFormat(),
-            mapping.mirror,
-            mapping.values.source(),
-            mapping.values.target()
+            sourceNameParts != null ? sourceNameParts[1] : mappingPrism.source(),
+            mappingPrism.expression(),
+            mappingPrism.target(),
+            mappingPrism.dateFormat(),
+            mappingPrism.mirror,
+            mappingPrism.values.source(),
+            mappingPrism.values.target()
         );
     }
 
@@ -98,12 +121,13 @@ public class Mapping {
         return parts;
     }
 
-    private Mapping(String sourceName, String sourceParameterName, String sourcePropertyName, String targetName,
-                    String dateFormat, AnnotationMirror mirror, AnnotationValue sourceAnnotationValue,
-                    AnnotationValue targetAnnotationValue) {
+    private Mapping(String sourceName, String sourceParameterName, String sourcePropertyName, String expression,
+                    String targetName, String dateFormat, AnnotationMirror mirror,
+                    AnnotationValue sourceAnnotationValue, AnnotationValue targetAnnotationValue) {
         this.sourceName = sourceName;
         this.sourceParameterName = sourceParameterName;
         this.sourcePropertyName = sourcePropertyName;
+        this.expression = expression;
         this.targetName = targetName.equals( "" ) ? sourceName : targetName;
         this.dateFormat = dateFormat;
         this.mirror = mirror;
@@ -139,6 +163,11 @@ public class Mapping {
         return sourceParameterName;
     }
 
+    public String getExpression() {
+        return expression;
+    }
+
+
     public String getTargetName() {
         return targetName;
     }
@@ -160,16 +189,22 @@ public class Mapping {
     }
 
     public Mapping reverse() {
-        return new Mapping(
-            targetName,
-            null,
-            targetName,
-            sourceName,
-            dateFormat,
-            mirror,
-            sourceAnnotationValue,
-            targetAnnotationValue
-        );
+        Mapping reverse = null;
+        if ( expression != null ) {
+            /* mapping can only be reversed if the source was not a constant */
+            reverse = new Mapping(
+                    targetName,
+                    null,
+                    targetName,
+                    expression,
+                    sourceName,
+                    dateFormat,
+                    mirror,
+                    sourceAnnotationValue,
+                    targetAnnotationValue
+            );
+        }
+        return reverse;
     }
 
     @Override

processor/src/main/java/org/mapstruct/ap/processor/MapperCreationProcessor.java

@@ -376,7 +376,10 @@ public class MapperCreationProcessor implements ModelElementProcessor<List<Sourc
                 if ( !reversed.containsKey( mapping.getTargetName() ) ) {
                     reversed.put( mapping.getTargetName(), new ArrayList<Mapping>() );
                 }
-                reversed.get( mapping.getTargetName() ).add( mapping.reverse() );
+                Mapping reverseMapping = mapping.reverse();
+                if ( reverseMapping != null ) {
+                    reversed.get( mapping.getTargetName() ).add( reverseMapping );
+                }
             }
         }
         return reversed;
@@ -387,12 +390,39 @@ public class MapperCreationProcessor implements ModelElementProcessor<List<Sourc
                                                SourceMethod method,
                                                ExecutableElement targetAcessor,
                                                Parameter parameter) {
-        String targetPropertyName = Executables.getPropertyName( targetAcessor );
+    String targetPropertyName = Executables.getPropertyName( targetAcessor );
+
+        // check if there's a mapping defined
         Mapping mapping = method.getMappingByTargetPropertyName( targetPropertyName );
-        String dateFormat = mapping != null ? mapping.getDateFormat() : null;
-        String sourcePropertyName = mapping != null ? mapping.getSourcePropertyName() : targetPropertyName;
+        String dateFormat = null;
+        boolean isSourceConstant = false;
+        String sourceConstant = null;
+        String sourcePropertyName;
+        if ( mapping != null ) {
+            dateFormat = mapping.getDateFormat();
+            isSourceConstant = !mapping.getExpression().isEmpty();
+            sourceConstant =  "\"" + mapping.getExpression() + "\"";
+            sourcePropertyName = mapping.getSourcePropertyName();
+        }
+        else {
+            sourcePropertyName = targetPropertyName;
+        }
+
         List<ExecutableElement> sourceGetters = parameter.getType().getGetters();
 
+        // check constants first
+        if ( isSourceConstant ) {
+            return getConstantMapping(
+                    mapperReferences,
+                    methods,
+                    method,
+                    sourceConstant,
+                    targetAcessor,
+                    dateFormat
+            );
+        }
+
+        // then iterate over source accessors (assuming the source is a bean)
         for ( ExecutableElement sourceAccessor : sourceGetters ) {
 
             List<Mapping> sourceMappings = method.getMappings().get( sourcePropertyName );
@@ -425,7 +455,6 @@ public class MapperCreationProcessor implements ModelElementProcessor<List<Sourc
                 );
             }
         }
-
         return null;
     }
 
@@ -592,10 +621,8 @@ public class MapperCreationProcessor implements ModelElementProcessor<List<Sourc
                     }
 
                 }
-                else if ( !hasSourceProperty(
-                    method,
-                    mappedProperty.getSourcePropertyName()
-                ) ) {
+                else if ( mappedProperty.getExpression().isEmpty() &&
+                          !hasSourceProperty( method, mappedProperty.getSourcePropertyName() ) ) {
                     messager.printMessage(
                         Kind.ERROR,
                         String.format(
@@ -627,7 +654,7 @@ public class MapperCreationProcessor implements ModelElementProcessor<List<Sourc
         return !foundUnmappedProperty;
     }
 
-    private PropertyMapping getPropertyMapping(List<MapperReference> mapperReferences,
+ private PropertyMapping getPropertyMapping(List<MapperReference> mapperReferences,
                                                List<SourceMethod> methods,
                                                SourceMethod method,
                                                Parameter parameter,
@@ -703,6 +730,78 @@ public class MapperCreationProcessor implements ModelElementProcessor<List<Sourc
         );
     }
 
+    private PropertyMapping getConstantMapping(List<MapperReference> mapperReferences,
+                                               List<SourceMethod> methods,
+                                               SourceMethod method,
+                                               String sourceReference,
+                                               ExecutableElement targetAcessor,
+                                               String dateFormat) {
+
+        // source
+       String mappedElement =  "constant '" + sourceReference + "'";
+       Type sourceType = typeFactory.getType( String.class );
+
+        // target
+        Type targetType = null;
+        if ( Executables.isSetterMethod( targetAcessor ) ) {
+            targetType = typeFactory.getSingleParameter( targetAcessor ).getType();
+        }
+        else if ( Executables.isGetterMethod( targetAcessor ) ) {
+            targetType = typeFactory.getReturnType( targetAcessor );
+        }
+        String targetPropertyName = Executables.getPropertyName( targetAcessor );
+
+
+        Assignment assignment = mappingResolver.getTargetAssignment(
+            method,
+            mappedElement,
+            mapperReferences,
+            methods,
+            sourceType,
+            targetType,
+            targetPropertyName,
+            dateFormat,
+            sourceReference
+        );
+
+        if ( assignment != null ) {
+
+            // create a new Map or Collection implementation if no method or type conversion
+            if ( targetType != null && ( targetType.isCollectionType() || targetType.isMapType() ) ) {
+                if ( assignment.isSimple() ) {
+                    assignment = new NewCollectionOrMapWrapper( assignment );
+                }
+            }
+
+            // target accessor is setter, so decorate assigmment as setter
+            assignment = new SetterWrapper( assignment );
+
+        }
+        else {
+            messager.printMessage(
+                    Kind.ERROR,
+                    String.format(
+                            "Can't map \"%s %s\" to \"%s %s\".",
+                            sourceType,
+                            sourceReference,
+                            targetType,
+                            Executables.getPropertyName( targetAcessor )
+                    ),
+                    method.getExecutable()
+            );
+        }
+        return new PropertyMapping(
+                null,
+                null,
+                null,
+                sourceType,
+                Executables.getPropertyName( targetAcessor ),
+                targetAcessor.getSimpleName().toString(),
+                targetType,
+                assignment
+        );
+    }
+
     private IterableMappingMethod getIterableMappingMethod(List<MapperReference> mapperReferences,
                                                            List<SourceMethod> methods,
                                                            SourceMethod method) {

processor/src/main/java/org/mapstruct/ap/processor/MethodRetrievalProcessor.java

@@ -384,11 +384,14 @@ public class MethodRetrievalProcessor implements ModelElementProcessor<Void, Lis
             if ( !mappings.containsKey( mappingAnnotation.source() ) ) {
                 mappings.put( mappingAnnotation.source(), new ArrayList<Mapping>() );
             }
-            mappings.get( mappingAnnotation.source() ).add( Mapping.fromMappingPrism( mappingAnnotation, method ) );
+            Mapping mapping =  Mapping.fromMappingPrism( mappingAnnotation, method, messager );
+            if ( mapping != null ) {
+                mappings.get( mappingAnnotation.source() ).add( mapping );
+            }
         }
 
         if ( mappingsAnnotation != null ) {
-            mappings.putAll( Mapping.fromMappingsPrism( mappingsAnnotation, method ) );
+            mappings.putAll( Mapping.fromMappingsPrism( mappingsAnnotation, method, messager ) );
         }
 
         return mappings;

processor/src/main/resources/org.mapstruct.ap.model.BeanMappingMethod.ftl

@@ -38,6 +38,9 @@
             <@includeModel object=propertyMapping targetBeanName=resultName existingInstanceMapping=existingInstanceMapping/>
         </#list>
     </#if>
+    <#list constantMappings as constantMapping>
+         <@includeModel object=constantMapping targetBeanName=resultName existingInstanceMapping=existingInstanceMapping/>
+    </#list>
     <#if returnType.name != "void">
 
     return ${resultName};

processor/src/test/java/org/mapstruct/ap/test/sourceconstants/ErroneousMapper1.java

@@ -0,0 +1,43 @@
+/**
+ *  Copyright 2012-2014 Gunnar Morling (http://www.gunnarmorling.de/)
+ *  and/or other contributors as indicated by the @authors tag. See the
+ *  copyright.txt file in the distribution for a full listing of all
+ *  contributors.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.mapstruct.ap.test.sourceconstants;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+import org.mapstruct.Mappings;
+import org.mapstruct.factory.Mappers;
+
+/**
+ *
+ * @author Sjaak Derksen
+ */
+@Mapper(uses = StringListMapper.class)
+public interface ErroneousMapper1 {
+
+    ErroneousMapper1 INSTANCE = Mappers.getMapper( ErroneousMapper1.class );
+
+    @Mappings( {
+        @Mapping( target = "stringConstant", expression = "stringConstant"),
+        @Mapping( source = "test" , target = "integerConstant", expression = "14"),
+        @Mapping( target = "longWrapperConstant", expression = "3001"),
+        @Mapping( target = "dateConstant", dateFormat = "dd-MM-yyyy", expression = "09-01-2014"),
+        @Mapping( target = "nameConstants", expression = "jack-jill-tom" )
+    } )
+    Target sourceToTarget(Source s);
+}

processor/src/test/java/org/mapstruct/ap/test/sourceconstants/ErroneousMapper2.java

@@ -0,0 +1,43 @@
+/**
+ *  Copyright 2012-2014 Gunnar Morling (http://www.gunnarmorling.de/)
+ *  and/or other contributors as indicated by the @authors tag. See the
+ *  copyright.txt file in the distribution for a full listing of all
+ *  contributors.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.mapstruct.ap.test.sourceconstants;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+import org.mapstruct.Mappings;
+import org.mapstruct.factory.Mappers;
+
+/**
+ *
+ * @author Sjaak Derksen
+ */
+@Mapper(uses = StringListMapper.class)
+public interface ErroneousMapper2 {
+
+    ErroneousMapper2 INSTANCE = Mappers.getMapper( ErroneousMapper2.class );
+
+    @Mappings( {
+        @Mapping( target = "stringConstant", expression = "stringConstant"),
+        @Mapping( target = "integerConstant" ),
+        @Mapping( target = "longWrapperConstant", expression = "3001"),
+        @Mapping( target = "dateConstant", dateFormat = "dd-MM-yyyy", expression = "09-01-2014"),
+        @Mapping( target = "nameConstants", expression = "jack-jill-tom" )
+    } )
+    Target sourceToTarget(Source s);
+}

processor/src/test/java/org/mapstruct/ap/test/sourceconstants/Source.java

@@ -0,0 +1,39 @@
+/**
+ *  Copyright 2012-2014 Gunnar Morling (http://www.gunnarmorling.de/)
+ *  and/or other contributors as indicated by the @authors tag. See the
+ *  copyright.txt file in the distribution for a full listing of all
+ *  contributors.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.mapstruct.ap.test.sourceconstants;
+
+/**
+ *
+ * @author Sjaak Derksen
+ */
+public class Source {
+
+    private String propertyThatShouldBeMapped;
+
+    public String getPropertyThatShouldBeMapped() {
+        return propertyThatShouldBeMapped;
+    }
+
+    public void setPropertyThatShouldBeMapped( String propertyThatShouldBeMapped ) {
+        this.propertyThatShouldBeMapped = propertyThatShouldBeMapped;
+    }
+
+
+
+}

processor/src/test/java/org/mapstruct/ap/test/sourceconstants/SourceConstantsTest.java

@@ -0,0 +1,122 @@
+/**
+ *  Copyright 2012-2014 Gunnar Morling (http://www.gunnarmorling.de/)
+ *  and/or other contributors as indicated by the @authors tag. See the
+ *  copyright.txt file in the distribution for a full listing of all
+ *  contributors.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.mapstruct.ap.test.sourceconstants;
+
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.util.Arrays;
+import java.util.Date;
+import javax.tools.Diagnostic.Kind;
+import static org.fest.assertions.Assertions.assertThat;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mapstruct.ap.testutil.IssueKey;
+import org.mapstruct.ap.testutil.WithClasses;
+import org.mapstruct.ap.testutil.compilation.annotation.CompilationResult;
+import org.mapstruct.ap.testutil.compilation.annotation.Diagnostic;
+import org.mapstruct.ap.testutil.compilation.annotation.ExpectedCompilationOutcome;
+import org.mapstruct.ap.testutil.runner.AnnotationProcessorTestRunner;
+
+/**
+ *
+ * @author Sjaak Derksen
+ */
+
+@RunWith(AnnotationProcessorTestRunner.class)
+public class SourceConstantsTest {
+
+    @Test
+    @IssueKey( "187" )
+    @WithClasses( {
+        Source.class,
+        Target.class,
+        SourceTargetMapper.class,
+        StringListMapper.class
+    } )
+    public void shouldMapSameSourcePropertyToSeveralTargetProperties() throws ParseException {
+        Source source = new Source();
+        source.setPropertyThatShouldBeMapped( "SomeProperty" );
+
+        Target target = SourceTargetMapper.INSTANCE.sourceToTarget( source );
+
+        assertThat( target ).isNotNull();
+        assertThat( target.getPropertyThatShouldBeMapped() ).isEqualTo( "SomeProperty" );
+        assertThat( target.getStringConstant() ).isEqualTo( "stringConstant" );
+        assertThat( target.getIntegerConstant() ).isEqualTo( 14 );
+        assertThat( target.getLongWrapperConstant() ).isEqualTo( new Long(3001L) );
+        assertThat( target.getDateConstant() ).isEqualTo( getDate( "dd-MM-yyyy", "09-01-2014") );
+        assertThat( target.getNameConstants() ).isEqualTo( Arrays.asList( "jack", "jill", "tom" ) );
+    }
+
+    @Test
+    @IssueKey( "187" )
+    @WithClasses( {
+        Source.class,
+        Target.class,
+        ErroneousMapper1.class,
+        StringListMapper.class
+    } )
+    @ExpectedCompilationOutcome(
+        value = CompilationResult.FAILED,
+        diagnostics = {
+            @Diagnostic(type = ErroneousMapper1.class,
+                kind = Kind.ERROR,
+                line = 42,
+                messageRegExp = "Source and expression are both defined in Mapping, either define a source or an "
+                        + "expression"),
+            @Diagnostic(type = ErroneousMapper1.class,
+                kind = Kind.WARNING,
+                line = 42,
+                messageRegExp = "Unmapped target property: \"integerConstant\"")
+        }
+    )
+    public void errorOnSourceAndExpression() throws ParseException {
+    }
+
+    @Test
+    @IssueKey( "187" )
+    @WithClasses( {
+        Source.class,
+        Target.class,
+        ErroneousMapper2.class,
+        StringListMapper.class
+    } )
+    @ExpectedCompilationOutcome(
+        value = CompilationResult.FAILED,
+        diagnostics = {
+            @Diagnostic(type = ErroneousMapper2.class,
+                kind = Kind.ERROR,
+                line = 42,
+                messageRegExp = "Either define a source or an expression in a Mapping"),
+            @Diagnostic(type = ErroneousMapper2.class,
+                kind = Kind.WARNING,
+                line = 42,
+                messageRegExp = "Unmapped target property: \"integerConstant\"")
+        }
+    )
+    public void errorOnNeitherSourceNorExpression() throws ParseException {
+    }
+
+    private Date getDate(String format, String date) throws ParseException {
+        SimpleDateFormat dateFormat = new SimpleDateFormat( format );
+        Date result = dateFormat.parse( date );
+        return result;
+    }
+
+}

processor/src/test/java/org/mapstruct/ap/test/sourceconstants/SourceTargetMapper.java

@@ -0,0 +1,43 @@
+/**
+ *  Copyright 2012-2014 Gunnar Morling (http://www.gunnarmorling.de/)
+ *  and/or other contributors as indicated by the @authors tag. See the
+ *  copyright.txt file in the distribution for a full listing of all
+ *  contributors.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.mapstruct.ap.test.sourceconstants;
+
+import org.mapstruct.Mapper;
+import org.mapstruct.Mapping;
+import org.mapstruct.Mappings;
+import org.mapstruct.factory.Mappers;
+
+/**
+ *
+ * @author Sjaak Derksen
+ */
+@Mapper(uses = StringListMapper.class)
+public interface SourceTargetMapper {
+
+    SourceTargetMapper INSTANCE = Mappers.getMapper( SourceTargetMapper.class );
+
+    @Mappings( {
+        @Mapping( target = "stringConstant", expression = "stringConstant"),
+        @Mapping( target = "integerConstant", expression = "14"),
+        @Mapping( target = "longWrapperConstant", expression = "3001"),
+        @Mapping( target = "dateConstant", dateFormat = "dd-MM-yyyy", expression = "09-01-2014"),
+        @Mapping( target = "nameConstants", expression = "jack-jill-tom" )
+    } )
+    Target sourceToTarget(Source s);
+}

processor/src/test/java/org/mapstruct/ap/test/sourceconstants/StringListMapper.java

@@ -0,0 +1,30 @@
+/**
+ *  Copyright 2012-2014 Gunnar Morling (http://www.gunnarmorling.de/)
+ *  and/or other contributors as indicated by the @authors tag. See the
+ *  copyright.txt file in the distribution for a full listing of all
+ *  contributors.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.mapstruct.ap.test.sourceconstants;
+
+import java.util.Arrays;
+import java.util.List;
+
+
+public class StringListMapper {
+
+    public List<String> stringToStringList(String string) {
+        return string == null ? null : Arrays.asList( string.split( "-" ) );
+    }
+}

processor/src/test/java/org/mapstruct/ap/test/sourceconstants/Target.java

@@ -0,0 +1,85 @@
+/**
+ *  Copyright 2012-2014 Gunnar Morling (http://www.gunnarmorling.de/)
+ *  and/or other contributors as indicated by the @authors tag. See the
+ *  copyright.txt file in the distribution for a full listing of all
+ *  contributors.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.mapstruct.ap.test.sourceconstants;
+
+import java.util.Date;
+import java.util.List;
+
+/**
+ *
+ * @author Sjaak Derksen
+ */
+public class Target {
+
+    private String propertyThatShouldBeMapped;
+    private String stringConstant;
+    private int integerConstant;
+    private Long longWrapperConstant;
+    private Date dateConstant;
+    private List<String> nameConstants;
+
+    public String getPropertyThatShouldBeMapped() {
+        return propertyThatShouldBeMapped;
+    }
+
+    public void setPropertyThatShouldBeMapped( String propertyThatShouldBeMapped ) {
+        this.propertyThatShouldBeMapped = propertyThatShouldBeMapped;
+    }
+
+    public String getStringConstant() {
+        return stringConstant;
+    }
+
+    public void setStringConstant( String stringConstant ) {
+        this.stringConstant = stringConstant;
+    }
+
+    public int getIntegerConstant() {
+        return integerConstant;
+    }
+
+    public void setIntegerConstant( int integerConstant ) {
+        this.integerConstant = integerConstant;
+    }
+
+    public Long getLongWrapperConstant() {
+        return longWrapperConstant;
+    }
+
+    public void setLongWrapperConstant( Long longWrapperConstant ) {
+        this.longWrapperConstant = longWrapperConstant;
+    }
+
+    public Date getDateConstant() {
+        return dateConstant;
+    }
+
+    public void setDateConstant( Date dateConstant ) {
+        this.dateConstant = dateConstant;
+    }
+
+    public List<String> getNameConstants() {
+        return nameConstants;
+    }
+
+    public void setNameConstants( List<String> nameConstants ) {
+        this.nameConstants = nameConstants;
+    }
+
+}