JSONMessageCodec.java

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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
package io.flutter.plugin.common;
 
import androidx.annotation.Nullable;
import java.nio.ByteBuffer;
import org.json.JSONException;
import org.json.JSONObject;
import org.json.JSONTokener;
 
/**
 * A {@link MessageCodec} using UTF-8 encoded JSON messages.
 *
 * <p>This codec is guaranteed to be compatible with the corresponding <a
 * href="https://api.flutter.dev/flutter/services/JSONMessageCodec-class.html">JSONMessageCodec</a>
 * on the Dart side. These parts of the Flutter SDK are evolved synchronously.
 *
 * <p>Supports the same Java values as {@link JSONObject#wrap(Object)}.
 *
 * <p>On the Dart side, JSON messages are handled by the JSON facilities of the <a
 * href="https://api.dartlang.org/stable/dart-convert/JSON-constant.html">dart:convert</a> package.
 */
public final class JSONMessageCodec implements MessageCodec<Object> {
  // This codec must match the Dart codec of the same name in package flutter/services.
  public static final JSONMessageCodec INSTANCE = new JSONMessageCodec();
 
  private JSONMessageCodec() {}
 
  @Override
  @Nullable
  public ByteBuffer encodeMessage(@Nullable Object message) {
    if (message == null) {
      return null;
    }
    final Object wrapped = JSONUtil.wrap(message);
    if (wrapped instanceof String) {
      return StringCodec.INSTANCE.encodeMessage(JSONObject.quote((String) wrapped));
    } else {
      return StringCodec.INSTANCE.encodeMessage(wrapped.toString());
    }
  }
 
  @Override
  @Nullable
  public Object decodeMessage(@Nullable ByteBuffer message) {
    if (message == null) {
      return null;
    }
    try {
      final String json = StringCodec.INSTANCE.decodeMessage(message);
      final JSONTokener tokener = new JSONTokener(json);
      final Object value = tokener.nextValue();
      if (tokener.more()) {
        throw new IllegalArgumentException("Invalid JSON");
      }
      return value;
    } catch (JSONException e) {
      throw new IllegalArgumentException("Invalid JSON", e);
    }
  }
}