elasticsearch - elasticsearch-创建TransportClient单例实例

Question

我正在尝试使用客户端的单例实例来创建多个索引。下面是相同的代码。但是每次我获取实例为null并创建一个新实例时。请让我知道我在做什么错

单例实例:

public class ESClientSingleton {

    public static Client instance ;

    private ESClientSingleton()
    {}

    public static Client getInstance()
    {
        if (instance == null)
          {
            System.out.println("the instance is null...");
            ImmutableSettings.Builder settings = ImmutableSettings.settingsBuilder(); 
                    settings.put("node.client", true); 
                    settings.put("node.data", false); 
                    settings.put("node.name", "node-client");
                    settings.put("cluster.name", "elasticsearch");
                    settings.build(); 
            instance = new TransportClient(settings)
                            .addTransportAddress(new InetSocketTransportAddress("10.203.251.142", 9300));
            //instance = client;
            System.out.println("return the client");
            return instance;
          }
        return instance;
    }       
}

调用方法:

public static IndexResponse insertESDocument(String nodeName, String json) throws MasterNotDiscoveredException, SocketException
  {  
      Client client = ESClientSingleton.getInstance();
      logger.debug("calling the es client");
      logger.debug("the json received as == "+json);
      IndexResponse response = client.prepareIndex("aricloud-nodes","node-entry",nodeName )
                               .setSource(json)
                               .execute()
                               .actionGet();
      logger.debug("the document is successfully indexed...");
              System.out.println("the document is indexed...");
              //client.close();
      return response;  
  } 

Answer 1

为了实现Singleton模式，请使用枚举代替类。
枚举具有许多内置优势，可帮助我们简化单例实现。
有关更多信息，请引用joshua bloch的Effective Java。