JsonObject.java

/*
 * Copyright (C) 2008 Google Inc.
 *
 * 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 com.google.gson;

import com.google.gson.internal.LinkedTreeMap;
import java.util.Map;
import java.util.Set;

/**
 * A class representing an object type in Json. An object consists of name-value pairs where names
 * are strings, and values are any other type of {@link JsonElement}. This allows for a creating a
 * tree of JsonElements. The member elements of this object are maintained in order they were added.
 * This class does not support {@code null} values. If {@code null} is provided as value argument
 * to any of the methods, it is converted to a {@link JsonNull}.
 *
 * <p>{@code JsonObject} does not implement the {@link Map} interface, but a {@code Map} view
 * of it can be obtained with {@link #asMap()}.
 *
 * @author Inderjeet Singh
 * @author Joel Leitch
 */
public final class JsonObject extends JsonElement {
  private final LinkedTreeMap<String, JsonElement> members = new LinkedTreeMap<>(false);

  /**
   * Creates an empty JsonObject.
   */
  @SuppressWarnings("deprecation") // superclass constructor
  public JsonObject() {
  }

  /**
   * Creates a deep copy of this element and all its children.
   *
   * @since 2.8.2
   */
  @Override
  public JsonObject deepCopy() {
    JsonObject result = new JsonObject();
    for (Map.Entry<String, JsonElement> entry : members.entrySet()) {
      result.add(entry.getKey(), entry.getValue().deepCopy());
    }
    return result;
  }

  /**
   * Adds a member, which is a name-value pair, to self. The name must be a String, but the value
   * can be an arbitrary {@link JsonElement}, thereby allowing you to build a full tree of JsonElements
   * rooted at this node.
   *
   * @param property name of the member.
   * @param value the member object.
   */
  public void add(String property, JsonElement value) {
    members.put(property, value == null ? JsonNull.INSTANCE : value);
  }

  /**
   * Removes the {@code property} from this object.
   *
   * @param property name of the member that should be removed.
   * @return the {@link JsonElement} object that is being removed, or {@code null} if no
   *   member with this name exists.
   * @since 1.3
   */
  public JsonElement remove(String property) {
    return members.remove(property);
  }

  /**
   * Convenience method to add a string member. The specified value is converted to a
   * {@link JsonPrimitive} of String.
   *
   * @param property name of the member.
   * @param value the string value associated with the member.
   */
  public void addProperty(String property, String value) {
    add(property, value == null ? JsonNull.INSTANCE : new JsonPrimitive(value));
  }

  /**
   * Convenience method to add a number member. The specified value is converted to a
   * {@link JsonPrimitive} of Number.
   *
   * @param property name of the member.
   * @param value the number value associated with the member.
   */
  public void addProperty(String property, Number value) {
    add(property, value == null ? JsonNull.INSTANCE : new JsonPrimitive(value));
  }

  /**
   * Convenience method to add a boolean member. The specified value is converted to a
   * {@link JsonPrimitive} of Boolean.
   *
   * @param property name of the member.
   * @param value the boolean value associated with the member.
   */
  public void addProperty(String property, Boolean value) {
    add(property, value == null ? JsonNull.INSTANCE : new JsonPrimitive(value));
  }

  /**
   * Convenience method to add a char member. The specified value is converted to a
   * {@link JsonPrimitive} of Character.
   *
   * @param property name of the member.
   * @param value the char value associated with the member.
   */
  public void addProperty(String property, Character value) {
    add(property, value == null ? JsonNull.INSTANCE : new JsonPrimitive(value));
  }

  /**
   * Returns a set of members of this object. The set is ordered, and the order is in which the
   * elements were added.
   *
   * @return a set of members of this object.
   */
  public Set<Map.Entry<String, JsonElement>> entrySet() {
    return members.entrySet();
  }

  /**
   * Returns a set of members key values.
   *
   * @return a set of member keys as Strings
   * @since 2.8.1
   */
  public Set<String> keySet() {
    return members.keySet();
  }

  /**
   * Returns the number of key/value pairs in the object.
   *
   * @return the number of key/value pairs in the object.
   * @since 2.7
   */
  public int size() {
    return members.size();
  }

  /**
   * Returns true if the number of key/value pairs in the object is zero.
   *
   * @return true if the number of key/value pairs in the object is zero.
   * @since $next-version$
   */
  public boolean isEmpty() {
    return members.size() == 0;
  }

  /**
   * Convenience method to check if a member with the specified name is present in this object.
   *
   * @param memberName name of the member that is being checked for presence.
   * @return true if there is a member with the specified name, false otherwise.
   */
  public boolean has(String memberName) {
    return members.containsKey(memberName);
  }

  /**
   * Returns the member with the specified name.
   *
   * @param memberName name of the member that is being requested.
   * @return the member matching the name, or {@code null} if no such member exists.
   */
  public JsonElement get(String memberName) {
    return members.get(memberName);
  }

  /**
   * Convenience method to get the specified member as a {@link JsonPrimitive}.
   *
   * @param memberName name of the member being requested.
   * @return the {@code JsonPrimitive} corresponding to the specified member, or {@code null} if no
   *   member with this name exists.
   * @throws ClassCastException if the member is not of type {@code JsonPrimitive}.
   */
  public JsonPrimitive getAsJsonPrimitive(String memberName) {
    return (JsonPrimitive) members.get(memberName);
  }

  /**
   * Convenience method to get the specified member as a {@link JsonArray}.
   *
   * @param memberName name of the member being requested.
   * @return the {@code JsonArray} corresponding to the specified member, or {@code null} if no
   *   member with this name exists.
   * @throws ClassCastException if the member is not of type {@code JsonArray}.
   */
  public JsonArray getAsJsonArray(String memberName) {
    return (JsonArray) members.get(memberName);
  }

  /**
   * Convenience method to get the specified member as a {@link JsonObject}.
   *
   * @param memberName name of the member being requested.
   * @return the {@code JsonObject} corresponding to the specified member, or {@code null} if no
   *   member with this name exists.
   * @throws ClassCastException if the member is not of type {@code JsonObject}.
   */
  public JsonObject getAsJsonObject(String memberName) {
    return (JsonObject) members.get(memberName);
  }

  /**
   * Returns a mutable {@link Map} view of this {@code JsonObject}. Changes to the {@code Map}
   * are visible in this {@code JsonObject} and the other way around.
   *
   * <p>The {@code Map} does not permit {@code null} keys or values. Unlike {@code JsonObject}'s
   * {@code null} handling, a {@link NullPointerException} is thrown when trying to add {@code null}.
   * Use {@link JsonNull} for JSON null values.
   *
   * @return mutable {@code Map} view
   * @since 2.10
   */
  public Map<String, JsonElement> asMap() {
    // It is safe to expose the underlying map because it disallows null keys and values
    return members;
  }

  /**
   * Returns whether the other object is equal to this. This method only considers
   * the other object to be equal if it is an instance of {@code JsonObject} and has
   * equal members, ignoring order.
   */
  @Override
  public boolean equals(Object o) {
    return (o == this) || (o instanceof JsonObject
        && ((JsonObject) o).members.equals(members));
  }

  /**
   * Returns the hash code of this object. This method calculates the hash code based
   * on the members of this object, ignoring order.
   */
  @Override
  public int hashCode() {
    return members.hashCode();
  }
}