Elasticsearch(ES)有两种连接方式：transport、rest。transport通过TCP方式访问ES(只支持java),rest方式通过http API 访问ES(没有语言限制)。

Transport

引入maven依赖

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>transport</artifactId>
    <version>${elasticsearch.version}</version>
</dependency>

创建transport client(5.x&6.X版本ES)


import org.elasticsearch.client.transport.TransportClient;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.transport.InetSocketTransportAddress;
import org.elasticsearch.transport.client.PreBuiltTransportClient;
  
Settings settings = Settings.builder()
 .put("cluster.name", "myClusterName")
 .put("client.transport.sniff", true)
 .build();
TransportClient client = new PreBuiltTransportClient(settings)
    .addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName("host1"), 9300));

设置client.transport.sniff为true来使客户端去嗅探整个集群的状态，把集群中其它机器的ip地址加到客户端中，这样做的好处是一般你不用手动设置集群里所有集群的ip到连接客户端，它会自动帮你添加，并且自动发现新加入集群的机器。

rest（已引入transport不能够再引入 rest，包会发生冲突）

官方提供low-level rest client(支持5.0及以后版本) 和high-level rest client(支持版本为 5.6及以后版本)

low-level rest client

引入maven依赖

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-client</artifactId>
    <version>6.5.4</version>
</dependency>

 <dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>rest</artifactId>
    <version>5.3.2</version>
</dependency>

创建rest client

Header[] defaultHeaders = new Header[] { new BasicHeader("header", "value") };
RestClient restClient = RestClient.builder(
        new HttpHost("localhost", 9200, "http"))
    .setDefaultHeaders(defaultHeaders) //设置默认标头
    .setMaxRetryTimeoutMillis(10000) //同一请求重试超时时间，默认30s
    .setFailureListener(new RestClient.FailureListener() {

    }) //设置侦听器，节点出现故障会收到通知
    .setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
        @Override
        public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpClientBuilder) {
            CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
            //create the authentication scope
            AuthScope authScope = new AuthScope(AuthScope.ANY_HOST, AuthScope.ANY_PORT, AuthScope
                .ANY_REALM);
            // Create credential pair(username,password)
            UsernamePasswordCredentials usernamePasswordCredentials = new UsernamePasswordCredentials("username", "password");
            credentialsProvider.setCredentials(authScope, usernamePasswordCredentials);
            return httpClientBuilder.setKeepAliveStrategy(new ConnectionKeepAliveStrategy() {
                @Override
                public long getKeepAliveDuration(HttpResponse response, HttpContext context) {
                    return 30 * 1000;
                }
            }).setDefaultCredentialsProvider(credentialsProvider);
        }
    })
    .setRequestConfigCallback(new RestClientBuilder.RequestConfigCallback() {
        @Override
        public RequestConfig.Builder customizeRequestConfig(RequestConfig.Builder requestConfigBuilder) {
            return requestConfigBuilder.setSocketTimeout(10000);
        }
    })
    .build();

high level rest client

引入maven依赖

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>rest</artifactId>
    <version>${elasticsearch.version}</version>
</dependency>

创建rest client

RestHighLevelClient client = new RestHighLevelClient(
  RestClient.builder(new HttpHost("localhost", 9200, "http")));

ES官方建议使用rest方式, transport 将计划在后面的版本中废弃。