4 在Java应用中访问ElasticSearch

4.1 在Java应用中实现查询文档

##pom中加入ElasticSearch6.2.4的依赖：

<dependencies>
    <dependency>
      <groupId>org.elasticsearch.client</groupId>
      <artifactId>transport</artifactId>
      <version>6.2.4</version>
    </dependency>    
    
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
  
  </dependencies> 
  
  <build>
      <plugins>
			<!-- java编译插件 -->
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.2</version>
				<configuration>
					<source>1.8</source>
					<target>1.8</target>
					<encoding>UTF-8</encoding>
				</configuration>
			</plugin>
		</plugins>
  </build>  

4.2 在Java应用中实现添加文档

              "{" +
                "\"id\":\"1\"," +
                "\"title\":\"Java设计模式之装饰模式\"," +
                "\"content\":\"在不必改变原类文件和使用继承的情况下，动态地扩展一个对象的功能。\"," +
                "\"postdate\":\"2018-05-20 14:38:00\"," +
                "\"url\":\"csdn.net/79239072\"" +
                "}"
 
 

 XContentBuilder doc1 = XContentFactory.jsonBuilder()
                    .startObject()
                    .field("id","3")
                    .field("title","Java设计模式之单例模式")
                    .field("content","枚举单例模式可以防反射攻击。")
                    .field("postdate","2018-02-03")
                    .field("url","csdn.net/79247746")
                    .endObject();
        
        IndexResponse response = client.prepareIndex("index1", "blog", null)
                .setSource(doc1)
                .get();
        
		System.out.println(response.status());
```		
### 4.3 在Java应用中实现删除文档

DeleteResponse response=client.prepareDelete(“index1”,“blog”,“SzYJjWMBjSAutsuLRP_P”).get();

//删除成功返回OK，否则返回NOT_FOUND

System.out.println(response.status());

### 4.4 在Java应用中实现更新文档

UpdateRequest request=new UpdateRequest(); request.index(“index1”) .type(“blog”) .id(“2”) .doc( XContentFactory.jsonBuilder().startObject() .field(“title”,“单例模式解读”) .endObject() ); UpdateResponse response=client.update(request).get();

//更新成功返回OK，否则返回NOT_FOUND

System.out.println(response.status());

upsert方式：

IndexRequest request1 =new IndexRequest(“index1”,“blog”,“3”) .source( XContentFactory.jsonBuilder().startObject() .field(“id”,“3”) .field(“title”,“装饰模式”) .field(“content”,“动态地扩展一个对象的功能”) .field(“postdate”,“2018-05-23”) .field(“url”,“csdn.net/79239072”) .endObject() ); UpdateRequest request2=new UpdateRequest(“index1”,“blog”,“3”) .doc( XContentFactory.jsonBuilder().startObject() .field(“title”,“装饰模式解读”) .endObject() ).upsert(request1);

UpdateResponse response=client.update(request2).get();

//upsert操作成功返回OK，否则返回NOT_FOUND

System.out.println(response.status());

### 4.5 在Java应用中实现批量操作

MultiGetResponse mgResponse = client.prepareMultiGet() .add(“index1”,“blog”,“3”,“2”) .add(“lib3”,“user”,“1”,“2”,“3”) .get();

for(MultiGetItemResponse response:mgResponse){ GetResponse rp=response.getResponse(); if(rp!=null && rp.isExists()){ System.out.println(rp.getSourceAsString()); } }

bulk：

BulkRequestBuilder bulkRequest = client.prepareBulk();

bulkRequest.add(client.prepareIndex(“lib2”, “books”, “4”) .setSource(XContentFactory.jsonBuilder() .startObject() .field(“title”, “python”) .field(“price”, 68) .endObject() ) ); bulkRequest.add(client.prepareIndex(“lib2”, “books”, “5”) .setSource(XContentFactory.jsonBuilder() .startObject() .field(“title”, “VR”) .field(“price”, 38) .endObject() ) ); //批量执行 BulkResponse bulkResponse = bulkRequest.get();

System.out.println(bulkResponse.status()); if (bulkResponse.hasFailures()) {

        System.out.println("存在失败操作");
    }

```

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