Allow Sets and Lists to be initialized to null (instead of an empty collection)

jsonschema2pojo-ant/src/main/java/org/jsonschema2pojo/ant/Jsonschema2PojoTask.java

@@ -96,6 +96,8 @@ public class Jsonschema2PojoTask extends Task implements GenerationConfig {
 
     private boolean useCommonsLang3 = false;
 
+    private boolean initializeEmptyCollections = true;
+
     /**
      * Execute this task (it's expected that all relevant setters will have been
      * called by Ant to provide task configuration <em>before</em> this method
@@ -405,7 +407,18 @@ public void setUseJodaDates(boolean useJodaDates) {
     public void setUseCommonsLang3(boolean useCommonsLang3) {
         this.useCommonsLang3 = useCommonsLang3;
     }
-
+
+
+    /**
+     * Sets the 'initializeEmptyCollections' property of this class
+     *
+     * @param initializeEmptyCollections
+     *            Whether to initialize collections with empty instance or null.
+     */
+    public void setInitializeEmptyCollections(boolean initializeEmptyCollections) {
+        this.initializeEmptyCollections = initializeEmptyCollections;
+    }
+
     @Override
     public boolean isGenerateBuilders() {
         return generateBuilders;
@@ -533,4 +546,9 @@ public FileFilter getFileFilter() {
         return new AllFileFilter();
     }
 
+    @Override
+    public boolean isInitializeEmptyCollections() {
+        return initializeEmptyCollections;
+    }
+
 }

jsonschema2pojo-ant/src/site/Jsonschema2PojoTask.html

@@ -170,6 +170,11 @@ <h3>Parameters</h3>
         <td valign="top">Whether to use primitives (<code>long</code>, <code>double</code>, <code>boolean</code>) instead of wrapper types where possible when generating bean properties (has the side-effect of making those.</td>
         <td align="center" valign="top">No (default <code>false</code>)</td>
       </tr>
+        <tr>
+            <td valign="top">initializeEmptyCollections</td>
+            <td valign="top">Whether to initialize collections with empty instance or <code>null</code>.</td>
+            <td align="center" valign="top">Yes (default <code>true</code>)</td>
+        </tr>
     </table>
 
     <h3>Examples</h3>

jsonschema2pojo-cli/src/main/java/org/jsonschema2pojo/cli/Arguments.java

@@ -100,6 +100,9 @@ public class Arguments implements GenerationConfig {
     @Parameter(names = { "-c3", "--commons-lang3" }, description = "Whether to use commons-lang 3.x imports instead of commons-lang 2.x imports when adding equals, hashCode and toString methods.")
     private boolean useCommonsLang3 = false;
 
+    @Parameter(names = { "-N", "--null-collections" }, description = "Initialize Set and List fields to null instead of an empty collection.")
+    private boolean omitInitializeEmptyCollections = false;
+
     private static final int EXIT_OKAY = 0;
     private static final int EXIT_ERROR = 1;
 
@@ -234,4 +237,9 @@ public FileFilter getFileFilter() {
         return new AllFileFilter();
     }
 
+    @Override
+    public boolean isInitializeEmptyCollections() {
+        return !omitInitializeEmptyCollections;
+    }
+
 }

jsonschema2pojo-core/src/main/java/org/jsonschema2pojo/DefaultGenerationConfig.java

@@ -157,7 +157,7 @@ public boolean isRemoveOldOutput() {
     public boolean isUseJodaDates() {
         return false;
     }
-    
+
     @Override
     public boolean isUseCommonsLang3() {
         return false;
@@ -167,4 +167,12 @@ public boolean isUseCommonsLang3() {
     public FileFilter getFileFilter() {
         return new AllFileFilter();
     }
-}
+
+    /**
+     * @return <code>true</code>
+     */
+    @Override
+    public boolean isInitializeEmptyCollections() {
+        return true;
+    }
+}

jsonschema2pojo-core/src/main/java/org/jsonschema2pojo/GenerationConfig.java

@@ -213,5 +213,11 @@ public interface GenerationConfig {
      * @return the file filter use when scanning for schema files.
      */
     FileFilter getFileFilter();
-
+
+    /**
+     * Gets the 'initializeEmptyCollections' configuration option.
+     *
+     * @return Whether to initialize collections with empty instance or null.
+     */
+    boolean isInitializeEmptyCollections();
 }

jsonschema2pojo-core/src/main/java/org/jsonschema2pojo/rules/DefaultRule.java

@@ -172,6 +172,8 @@ private JExpression getDefaultList(JType fieldType, JsonNode node) {
                 invokeAsList.arg(getDefaultValue(listGenericType, defaultValue));
             }
             newListImpl.arg(invokeAsList);
+        } else if (!ruleFactory.getGenerationConfig().isInitializeEmptyCollections()) {
+            return JExpr._null();
         }
 
         return newListImpl;
@@ -209,6 +211,8 @@ private JExpression getDefaultSet(JType fieldType, JsonNode node) {
                 invokeAsList.arg(getDefaultValue(setGenericType, defaultValue));
             }
             newSetImpl.arg(invokeAsList);
+        } else if (!ruleFactory.getGenerationConfig().isInitializeEmptyCollections()) {
+            return JExpr._null();
         }
 
         return newSetImpl;

jsonschema2pojo-gradle-plugin/src/main/groovy/org/jsonschema2pojo/gradle/JsonSchemaExtension.groovy

@@ -49,6 +49,7 @@ public class JsonSchemaExtension implements GenerationConfig {
   boolean useJodaDates
   boolean useCommonsLang3
   FileFilter fileFilter
+  boolean initializeEmptyCollections
 
   public JsonSchemaExtension() {
     // See DefaultGenerationConfig
@@ -69,6 +70,7 @@ public class JsonSchemaExtension implements GenerationConfig {
     useJodaDates = false
     useCommonsLang3 = false
     fileFilter = new AllFileFilter()
+    initializeEmptyCollections = true
   }
 
   @Override

jsonschema2pojo-maven-plugin/src/main/java/org/jsonschema2pojo/maven/Jsonschema2PojoMojo.java

@@ -309,6 +309,14 @@ public class Jsonschema2PojoMojo extends AbstractMojo implements GenerationConfi
      */
     private boolean useCommonsLang3 = false;
 
+    /**
+     * Whether to initialize collections with empty instance or null.
+     *
+     * @parameter expression="${jsonschema2pojo.initializeEmptyCollections}" default="true"
+     * @since
+     */
+    private boolean initializeEmptyCollections = true;
+
     /**
      * List of file patterns to include.
      * 
@@ -513,6 +521,11 @@ public FileFilter getFileFilter() {
         return fileFilter;
     }
 
+    @Override
+    public boolean isInitializeEmptyCollections() {
+        return initializeEmptyCollections;
+    }
+
     boolean filteringEnabled() {
         return !((includes == null || includes.length == 0) && (excludes == null || excludes.length == 0));
     }