RestHighLevelClient

一、创建连接
!ps:RestHighLevelClient是官方指定的连接API。另外一个是TransportClient，但是TransportClient这个是已经废弃不用的，所以会在ES8.0之后完全移除，也就是说8.0之后就无法使用了
RestHighLevelClient的maven依赖为（使用前必须添加相应依赖）

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-high-level-client</artifactId>
    <version>7.9.2</version>
</dependency>
        <dependency>
            <groupId>org.elasticsearch</groupId>
            <artifactId>elasticsearch</artifactId>
            <version>7.9.2</version>
 </dependency>

注意：以上的依赖版本可以根据你使用的ES的版本来定，向下兼容，但是无法向上兼容

创建连接

    static String ip = "localhost";
    static int port = 9200;
    static RestHighLevelClient restHighLevelClient = null;
    static TransportClient client = null;
    
    static  RestHighLevelClient initClient(){
        //这里的RestClient.builder(new HttpHost(ip,port),.........)支持多个httphost连接，也就是支持连接多个elasticsearch
        restHighLevelClient = new RestHighLevelClient(RestClient.builder(new HttpHost(ip,port)));
    }

    static Connection getInstance(){
        synchronized (ElasticSearchFactory.class){
            if (restHighLevelClient == null){
             restHighLevelClient  =   initClient();
            }
        }
        return connection;
    }

RestHighLevelClient 支持对ES的增删改查、批量操作
新增：

 public static  void creatIndex(String json){
        IndexRequest indexRequest = new IndexRequest("test_index","String");
        indexRequest.source(json, XContentType.JSON);//这里的json为存入ES的文档内容
        try {
            restHighLevelClient.index(indexRequest, RequestOptions.DEFAULT);//RequestOptions在新方法中必须选择
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

查询：
查询支持直接查询和条件查询，由于ES是根据索引、文档类型和文档ID确定一个唯一的文档的，所以直接查询必须要有索引和类型还有ID

    public static Map<String, Object> getIndex(String indexName,String type,String id){
        GetRequest request = new GetRequest(indexName);
        //SearchRequest searchRequest = new SearchRequest(indexName);
        try {
            GetResponse search = restHighLevelClient.get(request, RequestOptions.DEFAULT);
            Map<String, Object> source = search.getSource();
            return source;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return new HashMap<>();
    }
``

条件查询：
条件查询支持所有的ES的查询规则：![使用ES查询语句须知]{https://www.jianshu.com/p/cfbac15e0b7a}

public static Map<String, Object> searchIndex(String indexName){
    //GetRequest request = new GetRequest(indexName);
    //SearchRequest searchRequest = new SearchRequest(indexName);
    QueryBuilder queryBuilders = QueryBuilders.boolQuery().filter(
            QueryBuilders.termQuery("queryKey","吱吱吱ZZZ")
    );
    SearchRequest searchRequest = new SearchRequest();
    //searchRequest.indices("posts");这里可以设计GEET或者POST
    SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
    // searchSourceBuilder.sort(new ScoreSortBuilder().order(SortOrder.DESC));支持按评分排序，评分是指分词之后取得的文档相似度评分
    searchSourceBuilder.query(QueryBuilders.boolQuery().filter(QueryBuilders.termQuery("queryKey.keyword","吱吱吱ZZZ")));
    searchRequest.source(searchSourceBuilder);
    try {
        SearchResponse search = restHighLevelClient.search(searchRequest, RequestOptions.DEFAULT);
        SearchHit[] hits = search.getHits().getHits();
        for (SearchHit searchHit : hits){
            Map<String, Object> sourceAsMap = searchHit.getSourceAsMap();
            System.out.println("source : {}" + sourceAsMap.toString());
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
    return new HashMap<>();
}


修改：
ps:ES中其实并不存在真正意义上的修改，其实是进行的文档覆盖，先将原文档查出来标记删除，然后在原文档的基础上添加上修改形成一份新文档，存入ES中，之后再将打上删除标记的文档删除。

public static void updateIndex(String indexName, String type, String id, String json){
    UpdateRequest request = new UpdateRequest(indexName, type, id);

    request.doc(json, XContentType.JSON);
    try {
        UpdateResponse updateResponse = restHighLevelClient.update(request,RequestOptions.DEFAULT);
    } catch (IOException e) {
        e.printStackTrace();
    }
}


删除:

public static void deleteIndex(String indexName, String type, String id){
    DeleteRequest request = new DeleteRequest(indexName,type,id);
    try {
        restHighLevelClient.delete(request,RequestOptions.DEFAULT);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

bulk操作，bulk操作相当于批处理，能够在一次操作中处理一批数据，同时能够同时处理，增删改操作

public static void bulkIndex(){
        BulkRequest request = new BulkRequest();
        String jsonString="{\n" +
                "\t\"databaseId\": \"謝謝謝謝謝謝\",\n" +
                "\t\"databaseType\": \"嘻嘻嘻\",\n" +
                "\t\"queryKey\":\"吱吱吱ZZZ\"\n" +
                "}\n";
    UUID uuid = UUID.randomUUID();
    request.add(new IndexRequest("test_index", "String", uuid.toString())
                .source(jsonString,XContentType.JSON));
        String updateJson="{\n" +
                "  \"queryKey\":\"吱吱吱ZZZ\"\n" +
                "}";
        request.add(new UpdateRequest("test_index", "String", uuid.toString())
                .doc(updateJson,XContentType.JSON));
        request.add(new DeleteRequest("test_index", "String", uuid.toString()));

    try {
        restHighLevelClient.bulk(request, RequestOptions.DEFAULT);
    } catch (IOException e) {
        e.printStackTrace();
    }
}