Added deepMerge method to JsonObject

README.md

@@ -165,10 +165,11 @@ jsonObject.set("quantity", 24);
 jsonObject.remove("quantity");
 ```
 
-`JsonObject` also provides a `merge` method that copies all members from a given JSON object.
+`JsonObject` also provides a `merge` and a `deepMerge` method that copies all members from a given JSON object.
 
 ```java
 jsonObject.merge(otherObject);
+jsonObject.deepMerge(otherObject); // merges common object members recursively
 ```
 
 ### Output JSON

com.eclipsesource.json/src/main/java/com/eclipsesource/json/JsonObject.java

@@ -557,6 +557,34 @@ public JsonObject merge(JsonObject object) {
     return this;
   }
 
+  /**
+   * Copies all members of the specified object into this object. When the specified object contains
+   * members with names that also exist in this object, the existing values in this object will be
+   * replaced by the corresponding values in the specified object, except for the case that both values
+   * are JsonObjects themselves, which will trigger another merge of these objects
+   *
+   * @param object
+   *          the object to merge
+   * @return the object itself, to enable method chaining
+   */
+  public JsonObject deepMerge(JsonObject object) {
+    if (object == null) {
+      throw new NullPointerException("object is null");
+    }
+    for (Member member : object) {
+      final String name = member.name;
+      JsonValue value = member.value;
+      if (value instanceof JsonObject) {
+        final JsonValue existingValue = this.get(member.name);
+        if (existingValue instanceof JsonObject) {
+          value = ((JsonObject) existingValue).deepMerge((JsonObject) value);
+        }
+      }
+      this.set(name, value);
+    }
+    return this;
+  }
+
   /**
    * Returns the value of the member with the specified name in this object. If this object contains
    * multiple members with the given name, this method will return the last one.

com.eclipsesource.json/src/test/java/com/eclipsesource/json/JsonObject_Test.java

@@ -768,6 +768,41 @@ public void merge_replacesMembers() {
     assertEquals(Json.object().add("a", 1).add("b", 2).add("c", 1).add("d", 2), object);
   }
 
+  @Test
+  public void deepMerge_failsWithNull() {
+    assertException(NullPointerException.class, "object is null", new Runnable() {
+      public void run() {
+        object.deepMerge(null);
+      }
+    });
+  }
+
+  @Test
+  public void deepMerge_appendsMembers() {
+    object.add("a", 1).add("b", 1);
+    object.deepMerge(Json.object().add("c", 2).add("d", 2));
+
+    assertEquals(Json.object().add("a", 1).add("b", 1).add("c", 2).add("d", 2), object);
+  }
+
+  @Test
+  public void deepMerge_replacesMembers() {
+    object.add("a", 1).add("b", 1).add("c", 1);
+    object.deepMerge(Json.object().add("b", 2).add("d", 2));
+
+    assertEquals(Json.object().add("a", 1).add("b", 2).add("c", 1).add("d", 2), object);
+  }
+
+  @Test
+  public void deepMerge_mergesMemberObject() {
+    object.add("a", 1).add("b", Json.object().add("x", 1).add("y", 1)).add("c", Json.object().add("A", 1));
+    object.deepMerge(Json.object().add("b", Json.object().add("y", 2).add("z", 1)).add("c", 1)
+            .add("d", Json.object().add("B", 1)));
+
+    assertEquals(Json.object().add("a", 1).add("b", Json.object().add("x", 1).add("y", 2).add("z", 1)).add("c", 1)
+            .add("d", Json.object().add("B", 1)), object);
+  }
+
   @Test
   public void write_empty() throws IOException {
     JsonWriter writer = mock(JsonWriter.class);