es的rest-high-level-client使用

淩亂°似流年 2024-04-18 21:39 0阅读 0赞

**elasticsearch的官方文档的链接在此 **

[https://www.elastic.co/guide/en/elasticsearch/client/java-rest/current/index.html][https_www.elastic.co_guide_en_elasticsearch_client_java-rest_current_index.html]

如果不想看这文章, 请出门左转直接去看官方的api, 写的非常详细, 也写的很多

简单介绍下两种api

Java REST Client 有两种风格：
    
    Java Low Level REST Client ：用于Elasticsearch的官方低级客户端。它允许通过http与Elasticsearch集群通信。
    将请求编排和响应反编排留给用户自己处理。它兼容所有的Elasticsearch版本。
    （PS：学过WebService的话，对编排与反编排这个概念
    应该不陌生。可以理解为对请求参数的封装，以及对响应结果的解析）
    
    Java High Level REST Client ：用于Elasticsearch的官方高级客户端。它是基于低级客户端的，
    它提供很多API，并负责请求的编排与响应的反编排。
    （PS：就好比是，一个是传自己拼接好的字符串，并且自己解析返回的结果；而另一个是传对象，
    返回的结果也已经封装好了，
    直接是对象，更加规范了参数的名称以及格式，更加面对对象一点）
    （PS：所谓低级与高级，我觉得一个很形象的比喻是，面向过程编程与面向对象编程）
    使用需与ES版本保持一致
    
    在 Elasticsearch 7.0 中不建议使用TransportClient，并且在8.0中会完全删除TransportClient。
    因此，官方更建议我们用Java High Level REST Client，它执行HTTP请求，
    而不是序列号的Java请求。既然如此，这里就直接用高级了。

所以我就直接使用了es的最新版本7.3.1 , 这个es的启动需要jdk11, java的代码环境需要jdk8 以上.

当然了, 你可以和我一样装了jdk8 和11 ,然后在es的配置文件中加上这么一句

修改es的elasticsearch.bat 文件, 再最前面加上一个

set JAVA\_HOME=C:\\soft\\jdk11    就不会使用window配置的默认的jdk 了,使用11.

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**使用的maven坐标**

<dependencies>
            <dependency>
                <groupId>org.elasticsearch.client</groupId>
                <artifactId>elasticsearch-rest-high-level-client</artifactId>
                <version>7.3.1</version>
            </dependency>
            <dependency>
                <groupId>org.apache.logging.log4j</groupId>
                <artifactId>log4j-api</artifactId>
                <version>2.5</version>
            </dependency>
            <dependency>
                <groupId>org.apache.logging.log4j</groupId>
                <artifactId>log4j-core</artifactId>
                <version>2.5</version>
            </dependency>
        </dependencies>

**新建log4j2.xml, 一定要有这个, 不然启动报错.**

<?xml version="1.0" encoding="UTF-8"?>
    <Configuration status="WARN">
        <Appenders>
            <Console name="Console" target="SYSTEM_OUT">
                <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
            </Console>
        </Appenders>
        <Loggers>
            <Root level="error">
                <AppenderRef ref="Console" />
            </Root>
        </Loggers>
    </Configuration>

其实High Level REST Client 都有两种编程风格, 一种是同步的, 一种是异步的操作, 异步的操作添加一个监听器, 监听返回的结果即可.

在案例中了, 全部使用同步的进行操作.

package com.onyx;
    
    import org.apache.http.HttpHost;
    import org.elasticsearch.action.delete.DeleteRequest;
    import org.elasticsearch.action.delete.DeleteResponse;
    import org.elasticsearch.action.get.GetRequest;
    import org.elasticsearch.action.get.GetResponse;
    import org.elasticsearch.action.index.IndexRequest;
    import org.elasticsearch.action.index.IndexResponse;
    import org.elasticsearch.action.update.UpdateRequest;
    import org.elasticsearch.action.update.UpdateResponse;
    import org.elasticsearch.client.RequestOptions;
    import org.elasticsearch.client.RestClient;
    import org.elasticsearch.client.RestHighLevelClient;
    import org.elasticsearch.common.xcontent.XContentBuilder;
    import org.elasticsearch.common.xcontent.XContentFactory;
    import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
    
    import java.io.IOException;
    import java.util.Date;
    import java.util.HashMap;
    import java.util.Map;
    
    /**
     * @author zk
     * @Description: es的api crud的练习
     * @date 2019-09-12 8:50
     */
    public class UserCRUD {
    
        public static void main(String[] args) throws IOException, InterruptedException {
            RestHighLevelClient client = new RestHighLevelClient(
                    //因为使用的是http, 所以这里是9200 ,不是对应的9300,这是个大坑!
                    RestClient.builder(new HttpHost("localhost", 9200, "http")));
    
            //createDoc(client);
            //TimeUnit.SECONDS.sleep(2);
            //getDoc(client);
    
            //existsDoc(client);
            //deleteDoc(client);
    
            //updateDoc(client);
    
    
    
            client.close();
        }
    
    
        /**
         * 更新doc
         * @param client
         * @throws IOException
         */
        private static void updateDoc(RestHighLevelClient client) throws IOException {
            //不存在的更新会报错
            Map<String, Object> jsonMap = new HashMap<String, Object>();
            jsonMap.put("postDate", new Date());
            jsonMap.put("message", "daily update");
            UpdateRequest updateRequest = new UpdateRequest("posts", "3").doc(jsonMap);
            UpdateResponse updateResponse = client.update(updateRequest, RequestOptions.DEFAULT);
            System.out.println(updateResponse.status());
        }
    
    
        /**
         * 删除文档
         * @param client
         * @throws IOException
         */
        private static void deleteDoc(RestHighLevelClient client) throws IOException {
            DeleteRequest request = new DeleteRequest("posts", "1");
            DeleteResponse delete = client.delete(request, RequestOptions.DEFAULT);
            System.out.println(delete.status() + "~" + delete.getResult());
        }
    
    
        /**
         * 文档是否存在
         * @param client
         * @throws IOException
         */
        private static void existsDoc(RestHighLevelClient client) throws IOException {
            for (int i = 1; i <5; i++) {
                GetRequest request = new GetRequest("posts", String.valueOf(i));
                request.fetchSourceContext(new FetchSourceContext(false));
                request.storedFields("_none_");
                boolean exists = client.exists(request, RequestOptions.DEFAULT);
                System.out.println(exists);
            }
    
    
            /*GetRequest request2 = new GetRequest("posts", "5");
            request.fetchSourceContext(new FetchSourceContext(false));
            request.storedFields("_none_");
            boolean exists2 = client.exists(request2, RequestOptions.DEFAULT);
            System.out.println(exists2);*/
    
        }
    
    
        /**
         * 获取一个文档
         * @param client
         * @throws IOException
         */
        private static void getDoc(RestHighLevelClient client) throws IOException {
            //没有posts 会报错的
            GetRequest posts = new GetRequest("posts", "1");
            GetResponse response = client.get(posts, RequestOptions.DEFAULT);
            System.out.println(response.getId());
            System.out.println(response.getIndex());
            System.out.println(response.getSourceAsString());
            System.out.println(response.getSourceAsMap());
        }
    
    
        /**
         * 创建一个文档
         * @param client
         * @throws IOException
         */
        private static void createDoc(RestHighLevelClient client) throws IOException {
            IndexRequest request = new IndexRequest("posts");
            request.id("1");
            String jsonString = "{" +
                    "\"user\":\"zk\"," +
                    "\"postDate\":\"2019-01-30\"," +
                    "\"message\":\"trying out java\"" +
                    "}";
            String jsonString2 = "{" +
                    "\"user\":\"zk2\"," +
                    "\"postDate\":\"2019-10-01\"," +
                    "\"message\":\"trying out javascript\"" +
                    "}";
            //为什么这里要有个jsonString2 ,因为这个request.source(jsonString, jsonString2);
            // 的参数数量必须是偶数, 不然会报错的.
            request.source(jsonString, jsonString2);
            IndexResponse indexResponse = client.index(request, RequestOptions.DEFAULT);
            System.out.println(indexResponse.getResult());
    
    
            Map<String, Object> jsonMap = new HashMap<String, Object>();
            jsonMap.put("user", "ting");
            jsonMap.put("postDate", new Date());
            jsonMap.put("message", "trying out hadoop");
            IndexRequest post = new IndexRequest("post").id("2").source(jsonMap);
            client.index(post, RequestOptions.DEFAULT);
    
    
            XContentBuilder builder = XContentFactory.jsonBuilder();
            builder.startObject();
            {
                builder.field("user", "wang");
                builder.timeField("postDate", new Date());
                builder.field("message", "trying out scala");
            }
            builder.endObject();
            IndexRequest posts = new IndexRequest("posts").id("3").source(builder);
            client.index(posts, RequestOptions.DEFAULT);
    
    
            IndexRequest source = new IndexRequest("posts").id("4").source("user", "peng",
                    "postDate", new Date(),
                    "message", "trying out golang");
    
            client.index(source, RequestOptions.DEFAULT);
        }
    
    }

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[https_www.elastic.co_guide_en_elasticsearch_client_java-rest_current_index.html]: https://www.elastic.co/guide/en/elasticsearch/client/java-rest/current/index.html
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