Feature/json object merge (#12)

* added stub for new method to merge json objects together

* implemented JsonObject#merge method

Author: iamdudeman

src/main/java/technology/sola/json/JsonObject.java

@@ -164,10 +164,60 @@ public JsonElement put(String key, Boolean value) {
     return put(key, new JsonElement(value));
   }
 
+  /**
+   * Puts {@link JsonElement} of type {@link JsonElementType#NULL} into this {@link JsonObject}.
+   *
+   * @param key the key to put a NULL JSON value into
+   * @return the previous {@link JsonElement} associated with this key
+   */
   public JsonElement putNull(String key) {
     return put(key, new JsonElement());
   }
 
+  /**
+   * Merges this {@link JsonObject} with another resulting in a new {@code JsonObject}.
+   * <ol>
+   *   <li>If key in both and each value is an object then it will recursively merge and add to result</li>
+   *   <li>If key in both and each value is not an object, value from the right is added to the result</li>
+   *   <li>If key in this only, then this value is added to result</li>
+   *   <li>If key in other only, then other value is added to result</li>
+   * </ol>
+   * This does not create a deep copy of nested arrays and objects.
+   *
+   * @param other the object to merge with
+   * @return a new {@code JsonObject} with merged properties
+   */
+  public JsonObject merge(JsonObject other) {
+    JsonObject result = new JsonObject();
+
+    forEach((key, value) -> {
+      var otherValue = other.get(key);
+
+      // add in any unique keys from this object
+      if (otherValue == null) {
+        result.put(key, value);
+      } else {
+        // nested merge if value in both is an object
+        if (value.getType() == JsonElementType.JSON_OBJECT && otherValue.getType() == JsonElementType.JSON_OBJECT) {
+          result.put(key, value.asObject().merge(otherValue.asObject()));
+        } else {
+          result.put(key, otherValue);
+        }
+      }
+    });
+
+    // add in any unique keys from the other object
+    other.forEach((key, value) -> {
+      var thisValue = this.get(key);
+
+      if (thisValue == null) {
+        result.put(key, value);
+      }
+    });
+
+    return result;
+  }
+
   @Override
   public String toString() {
     return toString(0);
@@ -184,5 +234,6 @@ public String toString(int spaces) {
 
     solaJsonSerializer.getConfig().setSpaces(spaces);
 
-    return solaJsonSerializer.serialize(this);  }
+    return solaJsonSerializer.serialize(this);
+  }
 }

src/test/java/technology/sola/json/JsonObjectTest.java

@@ -135,4 +135,48 @@ void nullMethods() {
       assertTrue(root.isNull(TEST_KEY));
     }
   }
+
+  @Nested
+  class merge {
+    @Test
+    void shouldHaveUniqueKeysFromBothObjects() {
+      JsonObject objectOne = new JsonObject();
+
+      objectOne.put("test", 1);
+      JsonObject objectTwo = new JsonObject();
+      objectTwo.put("test2", 2);
+
+      JsonObject result = objectOne.merge(objectTwo);
+
+      assertEquals(1, result.getInt("test"));
+      assertEquals(2, result.getInt("test2"));
+    }
+
+    @Test
+    void shouldReplaceDuplicateKeysIfNotObjects() {
+      JsonObject objectOne = new JsonObject();
+      objectOne.put("test", 1);
+      JsonObject objectTwo = new JsonObject();
+      objectTwo.put("test", 2);
+
+      assertEquals(2, objectOne.merge(objectTwo).getInt("test"));
+      assertEquals(1, objectTwo.merge(objectOne).getInt("test"));
+    }
+
+    @Test
+    void shouldMergeNestedObjects() {
+      JsonObject objectOne = new JsonObject();
+      JsonObject objectOneNested = new JsonObject();
+      objectOne.put("test", objectOneNested);
+      objectOneNested.put("test", 1);
+
+      JsonObject objectTwo = new JsonObject();
+      JsonObject objectTwoNested = new JsonObject();
+      objectTwo.put("test", objectTwoNested);
+      objectTwoNested.put("test", 2);
+
+      assertEquals(2, objectOne.merge(objectTwo).getObject("test").getInt("test"));
+      assertEquals(1, objectTwo.merge(objectOne).getObject("test").getInt("test"));
+    }
+  }
 }