SpringBoot之操作Elasticsearch(基于RestTemplate方式实现)_elasticsearchresttemplate初始化

1.声明

当前内容主要用于本人学习和复习使用RestTemplate操作Elasticsearch,涉及到简单的查询操作

2.pom依赖

<parent>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-parent</artifactId>
	<version>2.2.5.RELEASE</version>
	<relativePath /> <!-- lookup parent from repository -->
</parent>
<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
<dependency>
	<groupId>org.projectlombok</groupId>
	<artifactId>lombok</artifactId>
</dependency>
<dependency>
	<groupId>org.projectlombok</groupId>
	<artifactId>lombok</artifactId>
</dependency>
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3.创建基本的配置和入口类以及实体类

@SpringBootApplication
public class ElasticsearchRestTemplateApplication {
	@Bean
	public RestTemplate restTemplate(){
		return new RestTemplate();
	}
	public static void main(String[] args) {
		SpringApplication.run(ElasticsearchRestTemplateApplication.class, args);
	}
}

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这里本人使用restTemplate.getForObject(URL, String.class);，所以后面需要分析结果

创建实体类：Person（对应查询后的返回结果的实体类）

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Person implements Serializable {
	private static final long serialVersionUID = 1L;
	private String user;
	private String title;
	private String desc;
}
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4.分析返回的结果

使用_search方式返回的结果：

hits->hits->_source集合

使用主键查询，/1方式的返回结果：

直接获取_source即可

5.通过上面分析的json结果创建工具类(默认使用jackson实现)

public abstract class ElasticsearchJsonFormatUtils {
	static ObjectMapper mapper = new ObjectMapper();
	static JsonFactory factory = mapper.getFactory();

	public static <T> List<T> getTargetsFromElasticsearch(String jsonStr, Class<T> clazz) {
		List<T> ts = new LinkedList<T>();
		try {
			TreeNode hits = findHits(jsonStr);
			for (int i = 0; i < hits.size(); i++) {
				TreeNode node = hits.get(i);
				T t = convertTreeNode(node, clazz);
				ts.add(t);
			}
			return ts;
		} catch (Exception e) {
			e.printStackTrace();
		}
		return ts;

	}

	private static TreeNode findHits(String jsonStr) {
		try {
			JsonParser createParser = factory.createParser(jsonStr);
			TreeNode readTree = mapper.readTree(createParser);
			TreeNode hits = readTree.get("hits").get("hits");
			return hits;
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}

	}

	private static <T> T convertTreeNode(TreeNode node, Class<T> clazz) {
		T t = null;
		Iterator<String> fieldNames = node.fieldNames();
		while (fieldNames.hasNext()) {
			String next = fieldNames.next();
			if (next.equals("_source")) {
				TreeNode source = node.get(next);
				return mapper.convertValue(source, clazz);
			}
		}
		return t;
	}

	public static <T> T getTargetFromElasticsearch(String jsonString, Class<T> clazz) {
		try {
			JsonParser createParser = factory.createParser(jsonString);
			TreeNode readTree = mapper.readTree(createParser);
			TreeNode treeNode = readTree.get("_source");
			T value = mapper.convertValue(treeNode, clazz);
			return value;
		} catch (IOException e) {
			e.printStackTrace();
			return null;
		}

	}
}

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6.创建controller类实现操作

@RestController
public class PersonController {
	@Autowired
	RestTemplate restTemplate;
	private static final String URL = "http://192.168.126.128:9200";

	@RequestMapping("/selectAll")
	public List<?> selectAll() {
		String resultStr = restTemplate.getForObject(URL + "/accounts/person/_search", String.class);
		System.out.println(resultStr);
		List<Person> persons = ElasticsearchJsonFormatUtils.getTargetsFromElasticsearch(resultStr, Person.class);
		return persons;
	}

	@RequestMapping("/selectById/{id}")
	public Person selectById(@PathVariable("id") Integer id) {
		String resultStr = restTemplate.getForObject(URL + "/accounts/person/" + id, String.class);
		System.out.println(resultStr);
		return ElasticsearchJsonFormatUtils.getTargetFromElasticsearch(resultStr, Person.class);
	}
}

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7.执行结果

操作成功，其他的删除修改操作可以看前面的文章！

8.总结

1.使用restTemplate操作Elasticsearch的时候，需要指定当前访问的url，还需要将需要的操作拼接，麻烦

2.获取返回数据的时候，默认结果是不同的，查询所有的时候需要解析两个hits,查询一个的时候只需要一个_source,解析工作复杂

==3.虽然上面的操作实现了基本的操作，但是过程过于复杂，需要分析返回结果==

以上纯属个人见解，如有问题请联系本人！