采用spring中的restTemplate实现httpClient远程调用服务

妖狐艹你老母 2024-04-17 22:59 70阅读 0赞

今天我来说说restTemplate吧，它是spring提供的一种远程调用服务的方式，底层封装了httpClient。我之前讲过的webservice是另一种远程调用服务的方式，它是基于http+xml的，平台无关性强。而httpclient是基于http的，一般用于浏览器发送，平台无关性弱。

### 讲restTemplate之前，先介绍它的api： ###

执行Get类型的Url，返回响应[`ResponseEntity`][ResponseEntity]或自己定义返回类型

执行Post类型的Url，返回响应[`ResponseEntity`][ResponseEntity]或自己定义返回类型

执行del类型的Url

<table> 
 <tbody> 
  <tr> 
   <td><code>void</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#delete-java.lang.String-java.util.Map-" rel="nofollow">delete</a>(java.lang.String&nbsp;url, java.util.Map&lt;java.lang.String,?&gt;&nbsp;uriVariables)</code></td> 
  </tr> 
  <tr> 
   <td><code>void</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#delete-java.lang.String-java.lang.Object...-" rel="nofollow">delete</a>(java.lang.String&nbsp;url, java.lang.Object...&nbsp;uriVariables)</code></td> 
  </tr> 
  <tr> 
   <td><code>void</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#delete-java.net.URI-" rel="nofollow">delete</a>(java.net.URI&nbsp;url)</code></td> 
  </tr> 
 </tbody> 
</table>

执行Put类型的Url

<table> 
 <tbody> 
  <tr> 
   <td><code>void</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#put-java.lang.String-java.lang.Object-java.util.Map-" rel="nofollow">put</a>(java.lang.String&nbsp;url, java.lang.Object&nbsp;request, java.util.Map&lt;java.lang.String,?&gt;&nbsp;uriVariables)</code></td> 
  </tr> 
  <tr> 
   <td><code>void</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#put-java.lang.String-java.lang.Object-java.lang.Object...-" rel="nofollow">put</a>(java.lang.String&nbsp;url, java.lang.Object&nbsp;request, java.lang.Object...&nbsp;uriVariables)</code></td> 
  </tr> 
  <tr> 
   <td><code>void</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#put-java.net.URI-java.lang.Object-" rel="nofollow">put</a>(java.net.URI&nbsp;url, java.lang.Object&nbsp;request)</code></td> 
  </tr> 
 </tbody> 
</table>

执行给定Url,并指定的请求[`RequestEntity`][RequestEntity]，最后返回响应[`ResponseEntity`][ResponseEntity]。

<table> 
 <tbody> 
  <tr> 
   <td><code>&lt;T&gt;&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/ResponseEntity.html" rel="nofollow">ResponseEntity</a>&lt;T&gt;</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#exchange-org.springframework.http.RequestEntity-java.lang.Class-" rel="nofollow">exchange</a>(<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/RequestEntity.html" rel="nofollow">RequestEntity</a>&lt;?&gt;&nbsp;requestEntity, java.lang.Class&lt;T&gt;&nbsp;responseType)</code> <p>&nbsp;</p> </td> 
  </tr> 
  <tr> 
   <td><code>&lt;T&gt;&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/ResponseEntity.html" rel="nofollow">ResponseEntity</a>&lt;T&gt;</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#exchange-org.springframework.http.RequestEntity-org.springframework.core.ParameterizedTypeReference-" rel="nofollow">exchange</a>(<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/RequestEntity.html" rel="nofollow">RequestEntity</a>&lt;?&gt;&nbsp;requestEntity,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/core/ParameterizedTypeReference.html" rel="nofollow">ParameterizedTypeReference</a>&lt;T&gt;&nbsp;responseType)</code></td> 
  </tr> 
  <tr> 
   <td><code>&lt;T&gt;&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/ResponseEntity.html" rel="nofollow">ResponseEntity</a>&lt;T&gt;</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#exchange-java.lang.String-org.springframework.http.HttpMethod-org.springframework.http.HttpEntity-java.lang.Class-java.util.Map-" rel="nofollow">exchange</a>(java.lang.String&nbsp;url,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpMethod.html" rel="nofollow">HttpMethod</a>&nbsp;method,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpEntity.html" rel="nofollow">HttpEntity</a>&lt;?&gt;&nbsp;requestEntity, java.lang.Class&lt;T&gt;&nbsp;responseType, java.util.Map&lt;java.lang.String,?&gt;&nbsp;uriVariables)</code></td> 
  </tr> 
  <tr> 
   <td><code>&lt;T&gt;&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/ResponseEntity.html" rel="nofollow">ResponseEntity</a>&lt;T&gt;</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#exchange-java.lang.String-org.springframework.http.HttpMethod-org.springframework.http.HttpEntity-java.lang.Class-java.lang.Object...-" rel="nofollow">exchange</a>(java.lang.String&nbsp;url,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpMethod.html" rel="nofollow">HttpMethod</a>&nbsp;method,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpEntity.html" rel="nofollow">HttpEntity</a>&lt;?&gt;&nbsp;requestEntity, java.lang.Class&lt;T&gt;&nbsp;responseType, java.lang.Object...&nbsp;uriVariables)</code></td> 
  </tr> 
  <tr> 
   <td><code>&lt;T&gt;&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/ResponseEntity.html" rel="nofollow">ResponseEntity</a>&lt;T&gt;</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#exchange-java.lang.String-org.springframework.http.HttpMethod-org.springframework.http.HttpEntity-org.springframework.core.ParameterizedTypeReference-java.util.Map-" rel="nofollow">exchange</a>(java.lang.String&nbsp;url,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpMethod.html" rel="nofollow">HttpMethod</a>&nbsp;method,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpEntity.html" rel="nofollow">HttpEntity</a>&lt;?&gt;&nbsp;requestEntity,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/core/ParameterizedTypeReference.html" rel="nofollow">ParameterizedTypeReference</a>&lt;T&gt;&nbsp;responseType, java.util.Map&lt;java.lang.String,?&gt;&nbsp;uriVariables)</code></td> 
  </tr> 
  <tr> 
   <td><code>&lt;T&gt;&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/ResponseEntity.html" rel="nofollow">ResponseEntity</a>&lt;T&gt;</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#exchange-java.lang.String-org.springframework.http.HttpMethod-org.springframework.http.HttpEntity-org.springframework.core.ParameterizedTypeReference-java.lang.Object...-" rel="nofollow">exchange</a>(java.lang.String&nbsp;url,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpMethod.html" rel="nofollow">HttpMethod</a>&nbsp;method,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpEntity.html" rel="nofollow">HttpEntity</a>&lt;?&gt;&nbsp;requestEntity,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/core/ParameterizedTypeReference.html" rel="nofollow">ParameterizedTypeReference</a>&lt;T&gt;&nbsp;responseType, java.lang.Object...&nbsp;uriVariables)</code></td> 
  </tr> 
  <tr> 
   <td><code>&lt;T&gt;&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/ResponseEntity.html" rel="nofollow">ResponseEntity</a>&lt;T&gt;</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#exchange-java.net.URI-org.springframework.http.HttpMethod-org.springframework.http.HttpEntity-java.lang.Class-" rel="nofollow">exchange</a>(java.net.URI&nbsp;url,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpMethod.html" rel="nofollow">HttpMethod</a>&nbsp;method,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpEntity.html" rel="nofollow">HttpEntity</a>&lt;?&gt;&nbsp;requestEntity, java.lang.Class&lt;T&gt;&nbsp;responseType)</code></td> 
  </tr> 
  <tr> 
   <td><code>&lt;T&gt;&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/ResponseEntity.html" rel="nofollow">ResponseEntity</a>&lt;T&gt;</code></td> 
   <td><code><a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/RestTemplate.html#exchange-java.net.URI-org.springframework.http.HttpMethod-org.springframework.http.HttpEntity-org.springframework.core.ParameterizedTypeReference-" rel="nofollow">exchange</a>(java.net.URI&nbsp;url,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpMethod.html" rel="nofollow">HttpMethod</a>&nbsp;method,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpEntity.html" rel="nofollow">HttpEntity</a>&lt;?&gt;&nbsp;requestEntity,&nbsp;<a href="https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/core/ParameterizedTypeReference.html" rel="nofollow">ParameterizedTypeReference</a>&lt;T&gt;&nbsp;responseType)</code></td> 
  </tr> 
 </tbody> 
</table>

主要选择get和post方式进行介绍

定义一个服务端：

package com.example.demo.controller;
    
    import com.example.demo.entity.User;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.PostMapping;
    import org.springframework.web.bind.annotation.RequestBody;
    import org.springframework.web.bind.annotation.RequestParam;
    import org.springframework.web.bind.annotation.RestController;
    
    /**
     * Created by linjiaming
     */
    @RestController
    public class TestController {
    
        @GetMapping("/getUser")
        public User getUser() {
            User u = new User();
            u.setName("getUser");
            return u;
        }
        
        @PostMapping("/postUser")
        public User postUser () {
            User u = new User();
            u.setName("postUser");
            return u;
        }
    
        @PostMapping("/postUserByName")
        public User postUser (@RequestBody User u) {
            return u;
        }
    }

分别是get，post无参，post有参方式

### 定义一个客户端： ###

package com.example.demo.controller;
    
    import com.example.demo.entity.User;
    import java.util.HashMap;
    import java.util.Map;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.http.HttpEntity;
    import org.springframework.http.HttpHeaders;
    import org.springframework.http.MediaType;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.PostMapping;
    import org.springframework.web.bind.annotation.RequestParam;
    import org.springframework.web.bind.annotation.RestController;
    import org.springframework.web.client.RestTemplate;
    
    /**
     * Created by linjiaming
     */
    @RestController
    public class TestController {
        @Autowired
        RestTemplate restTemplate;
    
        private static String GET_URL = "http://localhost:8080/getUser";
        private static String POST_URL = "http://localhost:8080/postUser";
        private static String POST_PARAM_URL = "http://localhost:8080/postUserByName";
    
    
        /**
         * 测试无参情况
         * @return
         */
        @GetMapping("/testgetUser")
        public User getUser() {
            //getForObject方式
            User user = restTemplate.getForObject(GET_URL, User.class);
    
            //getForEntity方式
            /*ResponseEntity<User> entity = restTemplate.getForEntity(GET_URL, User.class);
            User user = entity.getBody();*/
            return user;
        }
    
    
        @GetMapping("/testpostUser")
        public User postUser () {
            //PostForObject方式
            HttpHeaders headers = new HttpHeaders();
            headers.setContentType(MediaType.APPLICATION_JSON_UTF8);
            String data = "";
            HttpEntity<String> Entity = new HttpEntity<String>(data, headers);
            User user = restTemplate.postForObject(POST_URL, Entity, User.class);
    
            //PostForEntity方式
           /* HttpHeaders headers = new HttpHeaders();
            String data = "";
            HttpEntity<String> Entity = new HttpEntity<String>(data, headers);
            ResponseEntity<User> entity = restTemplate.postForEntity(POST_URL, Entity, User.class);
            User user = entity.getBody();*/
            return user;
        }
    
        @GetMapping("/testpostUserByName")
        public User postUserByName () {
            //PostForObject方式
            HttpHeaders headers = new HttpHeaders();
            headers.setContentType(MediaType.APPLICATION_JSON_UTF8);
            User u = new User();
            u.setName("lisi");
            u.setAge("18");
            HttpEntity<String> Entity = new HttpEntity(u,headers);
            User user = restTemplate.postForObject(POST_PARAM_URL, Entity, User.class);
    
            return user;
        }
    }

在定义这个controller之前，还需要配置restTemplate：

package com.example.demo.config;
    
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.http.client.ClientHttpRequestFactory;
    import org.springframework.http.client.SimpleClientHttpRequestFactory;
    import org.springframework.web.client.RestTemplate;
    
    /**
     * Created by linjiaming
     */
    @Configuration
    public class restTemplateConfig {
    
        @Bean
        public RestTemplate restTemplate(ClientHttpRequestFactory factory) {
            return new RestTemplate(factory);
        }
    
        @Bean
        public ClientHttpRequestFactory simpleClientHttpRequestFactory() {
            SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
            factory.setReadTimeout(5000);//ms
            factory.setConnectTimeout(15000);//ms
            return factory;
        }
    }

接下来可以测试一下效果了：

分别启动服务端（port：8080）和客户端（port：8081）

地址栏输入：[http://localhost:8081/testgetUser][http_localhost_8081_testgetUser]

结果：\{"name":"getUser","age":null\}

地址栏输入：[http://localhost:8081/testpostUser][http_localhost_8081_testpostUser]

结果：\{"name":"postUser","age":null\}

地址栏输入：[http://localhost:8081/testpostUserByName][http_localhost_8081_testpostUserByName]

结果：\{"name":"lisi","age":"18"\}

[ResponseEntity]: https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/ResponseEntity.html
[RequestEntity]: https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/RequestEntity.html
[http_localhost_8081_testgetUser]: http://localhost:8081/testgetUser
[http_localhost_8081_testpostUser]: http://localhost:8081/testpostUser
[http_localhost_8081_testpostUserByName]: http://localhost:8081/testpostUserByName