curator-x-discovery-server/src/main/java/org/apache/curator/x/discovery/server/entity/JsonServiceInstancesMarshaller.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.curator.x.discovery.server.entity;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ArrayNode;
import com.fasterxml.jackson.databind.node.ObjectNode;
import com.google.common.collect.Lists;
import org.apache.curator.x.discovery.ServiceInstance;
import org.apache.curator.x.discovery.server.rest.DiscoveryContext;
import javax.ws.rs.Consumes;
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.MessageBodyReader;
import javax.ws.rs.ext.MessageBodyWriter;
import javax.ws.rs.ext.Provider;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.util.List;

/**
 * Message body reader/writer. Inject this as appropriate for the JAX-RS implementation you are using
 */
@Provider
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)
public class JsonServiceInstancesMarshaller<T> implements MessageBodyReader<ServiceInstances<T>>, MessageBodyWriter<ServiceInstances<T>>
{
    private final DiscoveryContext<T> context;

    public JsonServiceInstancesMarshaller(DiscoveryContext<T> context)
    {
        this.context = context;
    }

    @Override
    public boolean isReadable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType)
    {
        return isWriteable(type, genericType, annotations, mediaType);
    }

    @Override
    public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType)
    {
        return ServiceInstances.class.isAssignableFrom(type) && mediaType.equals(MediaType.APPLICATION_JSON_TYPE);
    }

    @Override
    public long getSize(ServiceInstances<T> serviceInstances, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType)
    {
        return -1;
    }

    @Override
    public ServiceInstances<T> readFrom(Class<ServiceInstances<T>> type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, String> httpHeaders, InputStream entityStream) throws IOException, WebApplicationException
    {
        try
        {
            List<ServiceInstance<T>>    instances = Lists.newArrayList();
            ObjectMapper                mapper = new ObjectMapper();
            JsonNode                    tree = mapper.reader().readTree(entityStream);
            for ( int i = 0; i < tree.size(); ++i )
            {
                JsonNode                    node = tree.get(i);
                ServiceInstance<T> instance = JsonServiceInstanceMarshaller.readInstance(node, context);
                instances.add(instance);
            }
            return new ServiceInstances<T>(instances);
        }
        catch ( Exception e )
        {
            throw new WebApplicationException(e);
        }
    }

    @Override
    public void writeTo(ServiceInstances<T> serviceInstances, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) throws IOException, WebApplicationException
    {
        ObjectMapper mapper = new ObjectMapper();
        ArrayNode arrayNode = mapper.createArrayNode();
        List<? extends ServiceInstance<T>> instanceList = serviceInstances.getServices();
        for ( ServiceInstance<T> instance : instanceList )
        {
            ObjectNode node = JsonServiceInstanceMarshaller.writeInstance(mapper, instance, context);
            arrayNode.add(node);
        }
        mapper.writer().writeValue(entityStream, arrayNode);
    }
}