Elasticsearch Java High Level API 演示（一）- 简单文档操作

本系列文章旨在演示如何通过 Elasticsearch 官方的 Java 客户端连接，操作 Elasticsearch 服务，目标是让相关的Java开发人员快速上手，所以本文不会涉及 Elasticsearch 的相关理论。

环境准备

本文使用 Elasticsearch 服务的 7.5.2 版本，搭建的过程可以参考 在MacOS中安装Elasticsearch

Java 的版本是: JDK8

Elasticsearch 的Java客户端使用: Java High Level API 7.5

项目依赖及设置

在 IEDA 或 Eclipse 中新建一个 maven 项目，然后在 pom.xml 文件中添加如下依赖:

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>7.5.2</version>
</dependency>

        <!-- For Log -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-to-slf4j</artifactId>
    <version>2.11.1</version>
</dependency>

<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-api</artifactId>
    <version>1.7.24</version>
</dependency>

<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-simple</artifactId>
    <version>1.7.21</version>
</dependency>

并添加对 JDK8 的编译支持

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.6.1</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
    </plugins>
</build>

初始化链接

使用默认的 Elasticsearch 服务配置链接服务器

public static RestHighLevelClient connnect() {

    RestHighLevelClient client = new RestHighLevelClient(
            RestClient.builder(
                    new HttpHost("localhost", 9200, "http"),
                    new HttpHost("localhost", 9201, "http")));

    return client;
}

同步调用风格

建立单个文档(Index)

使用在connect方法中返回的连接

public static void createIndexSync(RestHighLevelClient client) {

    try {

        IndexRequest request = new IndexRequest("posts");
        request.id("1");
        String jsonString = "{" +
                "\"user\":\"kimchy\"," +
                "\"postDate\":\"2013-01-31\"," +
                "\"message\":\"trying out Elasticsearch\"" +
                "}";
        request.source(jsonString, XContentType.JSON);

        IndexResponse indexResponse = client.index(request, RequestOptions.DEFAULT);

        LOG.info("Complete the creation index: {}", indexResponse.status());

    } catch(Exception e) {

        LOG.error("Error when create index: ", e);

    } finally {
        if (client != null) {
            try {
                client.close();
            } catch(IOException e) { }
        }
    }

}

获取单个文档

public static void getIndexSync(RestHighLevelClient client) {

     try {

         GetRequest getRequest = new GetRequest(
                 "posts",
                 "1");

         GetResponse getResponse = client.get(getRequest, RequestOptions.DEFAULT);

         if (getResponse.isExists()) {

             LOG.info("Get Index: {}", getResponse.getSourceAsString());
         }


     } catch(Exception e) {

         LOG.error("Error when get index: ", e);

     } finally {
         if (client != null) {
             try {
                 client.close();
             } catch(IOException e) { }
         }
     }
 }

判断是否存在指定文档

public static void existSync(RestHighLevelClient client) {

    try {
        GetRequest getRequest = new GetRequest(
                "posts",
                "1");
        getRequest.fetchSourceContext(new FetchSourceContext(false));
        getRequest.storedFields("_none_");

        boolean exists = client.exists(getRequest, RequestOptions.DEFAULT);

        LOG.info("Exist: {}", exists);

    } catch(Exception e) {

        LOG.error("Error when exist: ", e);

    } finally {
        if (client != null) {
            try {
                client.close();
            } catch(IOException e) { }
        }
    }

}

删除单个文档

public static void deleteIndexSync(RestHighLevelClient client) {

    try {
        DeleteRequest request = new DeleteRequest(
                "posts",
                "1");

        DeleteResponse deleteResponse = client.delete(
                request, RequestOptions.DEFAULT);

        if (deleteResponse.status() == RestStatus.OK) {

            LOG.info("Deleted: {}", deleteResponse.getId());
        }

    } catch(Exception e) {

        LOG.error("Error when exist: ", e);

    } finally {
        if (client != null) {
            try {
                client.close();
            } catch(IOException e) { }
        }
    }

}

更新单个文档

public static void updateSync(RestHighLevelClient client) {

    try {

        UpdateRequest request = new UpdateRequest(
                "posts",
                "1")
                .doc("updated", new Date(),
                        "reason", "daily update");

        UpdateResponse updateResponse = client.update(
                request, RequestOptions.DEFAULT);

        if (updateResponse.status() == RestStatus.OK) {

            LOG.info("Update: {}", updateResponse.getId());
        }

    } catch(Exception e) {

        LOG.error("Error when update: ", e);

    } finally {
        if (client != null) {
            try {
                client.close();
            } catch(IOException e) { }
        }
    }
}

获取文档的结构和统计信息

public static void getTermVectorsSync(RestHighLevelClient client) {

    try {

        TermVectorsRequest request = new TermVectorsRequest("posts", "1");
        request.setFields("user");

        TermVectorsResponse response =
                client.termvectors(request, RequestOptions.DEFAULT);

        if (response.getFound()) {
            for (TermVectorsResponse.TermVector tv : response.getTermVectorsList()) {
                String fieldname = tv.getFieldName();
                int docCount = tv.getFieldStatistics().getDocCount();
                long sumTotalTermFreq =
                        tv.getFieldStatistics().getSumTotalTermFreq();
                long sumDocFreq = tv.getFieldStatistics().getSumDocFreq();

                LOG.info("fieldName = {}, docCount = {}, sumTotalTermFreq = {}", fieldname, sumTotalTermFreq, sumDocFreq);
            }
        }

    } catch(Exception e) {

        LOG.error("Error when Get Term Vectors: ", e);

    } finally {
        if (client != null) {
            try {
                client.close();
            } catch(IOException e) { }
        }
    }
}

如果对 Elasticsearch 的功能感兴趣，又希望能快速上手，可以试试 ElasticSearch教程