Java High Level REST Client

Java High Level REST Client 至少需要Java 1.8，它的主要目标是封装Elasticsearch REST API 提供易于编写的代码实现。

脚手架

git@github.com:nasuyun/example-springboot.git

cd example-springboot

vi ./src/main/resources/application.properties # 替换成你的应用用户名密码

mvn clean package

java -jar ./target/example-springboot-0.0.1.jar

依赖

• maven 依赖

pom.xml

        <dependency>
            <groupId>org.elasticsearch</groupId>
            <artifactId>elasticsearch</artifactId>
            <version>6.8.23</version>
        </dependency>
        <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>elasticsearch-rest-high-level-client</artifactId>
            <version>6.8.23</version>
        </dependency>

• gradle 依赖

build.gradle

dependencies {
    compile 'org.elasticsearch:elasticsearch:6.8.23'
    compile 'org.elasticsearch.client:elasticsearch-rest-high-level-client:6.8.23'
}

初始化客户端

首选 我们需要创建一个 RestHighLevelClient 实例，然后使用该实例进行索引的增删改查操作。

final String server = "https://router.nasuyun.com:9200";
final String username = "your_app_username";
final String password = "your_app_password";

// 构建ES客户端
RestHighLevelClient client() {
    Header[] headers = new Header[]{new BasicHeader(HttpHeaders.CONTENT_TYPE, "application/json")};
    final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
    credentialsProvider.setCredentials(AuthScope.ANY, new UsernamePasswordCredentials(username, password));
    RestClientBuilder builder = RestClient.builder(HttpHost.create(server))
            .setDefaultHeaders(headers)
            .setHttpClientConfigCallback(httpClientBuilder -> httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider));
    return new RestHighLevelClient(builder);
}

正确的关闭客户端

在使用RestHighLevelClient进行相关操作后，我们需要根据场景正确的调用client.close()释放它的资源。

• 低频场景 例如创建索引、删除索引、修改mapping等元数据操作， 应采用用完即释放的方式。

try (RestHighLevelClient client = client()) {
    // 操作
    client.dosomething ...
} catch (Exception e) {
    log.error("", e);
}
// try-with-resource 自动调用 client.clsoe()释放

• 高频场景 例如持续高并发的写入或查询索引，应采用连接复用的方式

    
final RestHighLevelClient client;

// 在构造阶段创建RestHighLevelClient实例
Operator() {
    client = client();
}

void write() {
    bulk by client ...
}

void search() {
    search by client ...
}    

// 当业务应用关闭时调用close
void close() {
    client.close();
}      

tip

高频场景：应避免频繁创建client导致socket端口耗尽。