elasticSearch之java客户端开发，demo演示_elasticsearch java demo

作者：盐析白兔 | 2024-04-16 12:46:32

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elasticsearch java demo

使用java操作es集群很简单，只需要在pom文件里引入es客户端的依赖即可，如下：

<dependency>
          <groupId>org.elasticsearch.client</groupId>
          <artifactId>elasticsearch-rest-high-level-client</artifactId>
          <version>6.6.1</version>
</dependency>
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下面记录一下几个基本的api操作：

1.使用java连接ES集群

es官方从6.0开始推荐大家使用高级客户端连接es集群，并在7.0以后摒弃了低级客户端通信。所以这里用高级客户端RestHighLevelClient作为案例，注意客户端的版本号要与集群主版本号保持一致，我的es版本号是6.6.1，所以这里客户端版本号也采用6.6.1，代码如下：

public class ElasticSearchClient {
    /**
     * 使用RestHighLevelClient连接elasticsearch集群测试
     * @throws IOException
     */
    @Test
    public void test1() throws IOException {
        RestHighLevelClient client = new RestHighLevelClient(RestClient.builder(new HttpHost("192.168.137.228",9200,"http")));
        GetRequest getRequest = new GetRequest("test","user","1");
         getRequest.fetchSourceContext(new FetchSourceContext(false));
        getRequest.storedFields("_none_");
        boolean exist = client.exists(getRequest, RequestOptions.DEFAULT);
        if(exist){
            System.out.println("文档存在");
        }else {
            System.out.println("文档不存在");
        }
        client.close();
    }
}
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以上代码示例了一个连接es集群，并从es集群获取索引为test，类型为user，id为1的记录。

2.ES documentAPI-索引index

es官方提供了非常丰富的api来对es集群做一系列的操作，具体详细的说明，有兴趣的同学可以去es官网查看api详解，这里只做demo演示。

/**
 * elasticsearch连接集群创建索引的四种方法
 */
public class ElasticSearchDocumentAPI {
    public RestHighLevelClient restHighLevelClient;

    @BeforeEach
    public void connectES(){
        restHighLevelClient = new RestHighLevelClient(RestClient.builder(new HttpHost("192.168.137.228",9200,"http")));
    }

    /**
     * es创建索引API，方法一，使用json串
     */
    @Test
    public void testIndex() throws IOException {
        String jsonString ="{"+
                "    \"user\" : \"kimchy\",\n" +
                "    \"post_date\" : \"2009-11-15T14:12:12\",\n" +
                "    \"message\" : \"trying out Elasticsearch\"\n" +
                "}";

        IndexRequest request = new IndexRequest("posts","doc","2");
        request.source(jsonString,XContentType.JSON);
        IndexResponse response = restHighLevelClient.index(request,RequestOptions.DEFAULT );
        System.out.println(response.getId());
        restHighLevelClient.close();
    }

    /**
     * es创建索引API，方法二,MAP
     */
    @Test
    public void testIndex2() throws IOException {
        Map<String,Object> jsonMap = new HashMap<String, Object>();
        jsonMap.put("user", "kimchy");
        jsonMap.put("post_date", "2009-11-15T14:12:12");
        jsonMap.put("message", "trying out Elasticsearch");

        IndexRequest request = new IndexRequest("posts","doc","3");
        request.source(jsonMap);
        IndexResponse response = restHighLevelClient.index(request,RequestOptions.DEFAULT );
        System.out.println(response.getId());
        restHighLevelClient.close();
    }

    /**
     * es创建索引API，方法三，XContentBuilder
     */
    @Test
    public void testIndex3() throws IOException {
        XContentBuilder builder = XContentFactory.jsonBuilder();
        builder.startObject();
        {
            builder.field("user","kimchy");
            builder.field("post_date",new Date());
            builder.field("message","trying out Elasticsearch");
        }
        builder.endObject();

        IndexRequest request = new IndexRequest("posts","doc","4");
        request.source(builder);
        IndexResponse response = restHighLevelClient.index(request,RequestOptions.DEFAULT );
        System.out.println(response.getId());
        restHighLevelClient.close();
    }

    /**
     * es创建索引API，方法四，Object
     */
    @Test
    public void testIndex4() throws IOException {

        IndexRequest request = new IndexRequest("posts","doc","5")
                .source("user","kimchy",
                        "post_date",new Date(),
                        "message","trying out Elasticsearch");

        IndexResponse response = restHighLevelClient.index(request,RequestOptions.DEFAULT );
        System.out.println(response.getId());
        restHighLevelClient.close();
    }
}
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3.索引查询

下面演示的是一个通过api查询索引的demo

  /**
     * 从es查询索引get
     * @throws IOException
     */
    @Test
    public void testGet() throws IOException {
  		RestHighLevelClient restHighLevelClient= new RestHighLevelClient(RestClient.builder(new HttpHost("192.168.137.228",9200,"http")));
        GetRequest request = new GetRequest("posts","doc","5");

        GetResponse response = restHighLevelClient.get(request,RequestOptions.DEFAULT );
        System.out.println(response.getSource());
        restHighLevelClient.close();
    }
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4.判断索引是否存在

这个代码在上面有提到，通过调用exists来实现

public class ElasticSearchClient {
    /**
     * 使用RestHighLevelClient连接elasticsearch集群测试
     * @throws IOException
     */
    @Test
    public void test1() throws IOException {
        RestHighLevelClient client = new RestHighLevelClient(RestClient.builder(new HttpHost("192.168.137.228",9200,"http")));
        GetRequest getRequest = new GetRequest("test","user","1");
         getRequest.fetchSourceContext(new FetchSourceContext(false));
        getRequest.storedFields("_none_");
        boolean exist = client.exists(getRequest, RequestOptions.DEFAULT);
        if(exist){
            System.out.println("文档存在");
        }else {
            System.out.println("文档不存在");
        }
        client.close();
    }
}
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5.索引更新

如下：索引中有对应的字段就更新，没有就添加

/**
     * 从es更新索引update
     * @throws IOException
     */
    @Test
    public void testUpdate() throws IOException {
		RestHighLevelClient restHighLevelClient= new RestHighLevelClient(RestClient.builder(new HttpHost("192.168.137.228",9200,"http")));
        UpdateRequest request = new UpdateRequest("posts","doc","1");
        String jsonString ="{"+
                "    \"updated\" : \"2019-07-27\",\n" +
                "    \"reason\" : \"daily update\"\n" +
                "}";
        request.doc(jsonString,XContentType.JSON);

        UpdateResponse response = restHighLevelClient.update(request,RequestOptions.DEFAULT );
        System.out.println(response.getGetResult());
        restHighLevelClient.close();
    }
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6.索引删除

注意es的删除操作是标记删除，并不会马上生效，它会在你之后添加更多索引的时候进行清理，代码如下：

/**
     * 从es删除索引delete
     * @throws IOException
     */
    @Test
    public void testDelete() throws IOException {
		RestHighLevelClient restHighLevelClient= new RestHighLevelClient(RestClient.builder(new HttpHost("192.168.137.228",9200,"http")));
        DeleteRequest request = new DeleteRequest("posts","doc","5");

        DeleteResponse response = restHighLevelClient.delete(request,RequestOptions.DEFAULT );
        restHighLevelClient.close();
    }
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7.ES批量操作bulk

es提供了buik对应api来执行java客户端批量新增、更改、删除，如下：

 /**
     * 批量操作bulk
     * @throws IOException
     */
    @Test
    public void testBulk() throws IOException {
		RestHighLevelClient restHighLevelClient= new RestHighLevelClient(RestClient.builder(new HttpHost("192.168.137.228",9200,"http")));
        BulkRequest request = new BulkRequest();
        request.add(new IndexRequest("posts","doc","5").source("field","foo"));
        request.add(new IndexRequest("posts","doc","4").source("field","bar"));
        request.add(new IndexRequest("posts","doc","3").source("field","baz"));

        BulkResponse response = restHighLevelClient.bulk(request,RequestOptions.DEFAULT );
        if(response.hasFailures()){ //如果有失败的请求,遍历打印请求信息
            for (BulkItemResponse bulkItemResponse:response){
                BulkItemResponse.Failure failure = bulkItemResponse.getFailure();
                System.out.println(failure.getMessage());
            }
        }
        restHighLevelClient.close();
    }
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8.批量查询索引mget

/**
     * 批量查询 mget
     * @throws IOException
     */
    @Test
    public void testMget() throws IOException {
    	RestHighLevelClient restHighLevelClient= new RestHighLevelClient(RestClient.builder(new HttpHost("192.168.137.228",9200,"http")));
        MultiGetRequest request = new MultiGetRequest();
        request.add(new MultiGetRequest.Item("test","user","1"));
        request.add(new MultiGetRequest.Item("test","user","2"));
        MultiGetResponse responses = restHighLevelClient.mget(request, RequestOptions.DEFAULT);
        //遍历得到的结果,并输出
        for(MultiGetItemResponse itemResponse:responses){
            GetResponse response = itemResponse.getResponse();
            if(response.isExists()){
                System.out.println(response.getSourceAsString());
            }
        }
        restHighLevelClient.close();
    }
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9.SearchType

es把数据存在了多个分片中，查询的时候会把请求分发到这多个分片中，各个分片都会返回查询结果，最后对这些结果做聚合。由此衍生出了几种查询类型：
Search and fetch：向所有分片发送查询请求，所有分片将查询结果返回后聚合。查询速率快，但是结果数据量可能比预期大很多
Search then fetch：向所有分片发送查询请求，各分片只返回文档id和排名相关信息，聚合后进行一个总得排名，最后取前n个，根据文档id再去对应的分片查询文档内容，这样的好处是得到的数据量是和预期一样的，但因为各个分片的打分标准不一样，可能导致得到的数据不准确
DFS Search and fetch：它的排序方法和第一种方法大致一样，只不过它在查询前，先给所有分片发请求，将所有分片文档的频率和词频汇总到一起，统一各个分片的打分标准，在进行后面的排序。这么做返回的结果准确，但是返回的数据量可能比预期大很多
DFS Search then fetch：它的排序方法和第二种方法大致一样，但也是在查询前对各分片打分标准做了统一，他的优点是返回的数据量和数据都是准确的，但是查询效率最低，但在可容忍范围内。
用户可以根据实际需求对排序标准做选择

 /**
     *SearchType
     */
    @Test
    public void testSearchType() throws IOException {
   		 RestHighLevelClient restHighLevelClient= new RestHighLevelClient(RestClient.builder(new HttpHost("192.168.137.228",9200,"http")));
        SearchRequest searchRequest = new SearchRequest();
        SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
        searchSourceBuilder.query(QueryBuilders.termQuery("age", 28));
        searchRequest.source(searchSourceBuilder);  //设置获取数据内容
        searchRequest.indices("test");              //设置索引
        searchRequest.types("user");                //设置类型
        searchRequest.searchType(SearchType.QUERY_THEN_FETCH);  //设置searchType

        SearchResponse searchResponse = restHighLevelClient.search(searchRequest, RequestOptions.DEFAULT);
        SearchHits hits = searchResponse.getHits();
        System.out.println(hits.getTotalHits());
        restHighLevelClient.close();
    }
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ES客户端还提供了其他许多的api，这里不一一记录，有兴趣的同学可自行前往官网查看

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