hadoop-common-project/hadoop-kms/src/main/java/org/apache/hadoop/crypto/key/kms/server/KMSJSONWriter.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.crypto.key.kms.server;

import org.apache.hadoop.classification.InterfaceAudience;
import org.codehaus.jackson.map.ObjectMapper;

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.Charset;
import java.util.List;
import java.util.Map;

/**
 * Jersey provider that converts <code>Map</code>s and <code>List</code>s
 * to their JSON representation.
 */
@Provider
@Produces(MediaType.APPLICATION_JSON)
@InterfaceAudience.Private
public class KMSJSONWriter implements MessageBodyWriter<Object> {

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

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

  @Override
  public void writeTo(Object obj, Class<?> aClass, Type type,
      Annotation[] annotations, MediaType mediaType,
      MultivaluedMap<String, Object> stringObjectMultivaluedMap,
      OutputStream outputStream) throws IOException, WebApplicationException {
    Writer writer = new OutputStreamWriter(outputStream, Charset
        .forName("UTF-8"));
    ObjectMapper jsonMapper = new ObjectMapper();
    jsonMapper.writerWithDefaultPrettyPrinter().writeValue(writer, obj);
  }

}