hadoop-hdfs-project/hadoop-hdfs-httpfs/src/main/java/org/apache/hadoop/lib/wsrs/JSONMapProvider.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.hadoop.lib.wsrs;

import org.apache.hadoop.classification.InterfaceAudience;
import org.json.simple.JSONObject;

import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.nio.charset.StandardCharsets;
import java.util.Map;

@Provider
@Produces(MediaType.APPLICATION_JSON)
@InterfaceAudience.Private
public class JSONMapProvider implements MessageBodyWriter<Map> {
  private static final String ENTER = System.getProperty("line.separator");

  @Override
  public boolean isWriteable(Class<?> aClass, Type type, Annotation[] annotations, MediaType mediaType) {
    return Map.class.isAssignableFrom(aClass);
  }

  @Override
  public long getSize(Map map, Class<?> aClass, Type type, Annotation[] annotations, MediaType mediaType) {
    return -1;
  }

  @Override
  public void writeTo(Map map, Class<?> aClass, Type type, Annotation[] annotations,
                      MediaType mediaType, MultivaluedMap<String, Object> stringObjectMultivaluedMap,
                      OutputStream outputStream) throws IOException, WebApplicationException {
    Writer writer =
        new OutputStreamWriter(outputStream, StandardCharsets.UTF_8);
    JSONObject.writeJSONString(map, writer);
    writer.write(ENTER);
    writer.flush();
  }

}