springboot使用RestTemplate实现远程调用服务

简介

spring框架提供的RestTemplate类可用于在应用中调用rest服务，它简化了与http服务的通信方式，统一了RESTful的标准，封装了http链接，我们只需要传入url及返回值类型即可。相较于之前常用的HttpClient，RestTemplate是一种更优雅的调用RESTful服务的方式。

RestTemplate默认依赖JDK提供http连接的能力（HttpURLConnection），如果有需要的话也可以通过setRequestFactory方法替换为例如Apache HttpComponents、Netty或OkHttp等其它HTTP library。

其实spring并没有真正的去实现底层的http请求（3次握手），而是集成了别的http请求，spring只是在原有的各种http请求进行了规范标准，让开发者更加简单易用，底层默认用的是jdk的http请求。

首先咋门搭建两个服务，一个接口提供者，一个接口调用者

接口提供者环境准备

1，application.yml

server:
  port: 9005
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/myqx?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
    username: root
    password: 1234

2，提供接口，供以调用

@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserInfoService userInfoService;

    @GetMapping("/params/{id}")
    public String findAll(@PathVariable("id") Integer id) {
        System.out.println(id);
        return "myqxin";
    }

    @GetMapping("/get")
    public List<UserInfo> findAll() {
        List<UserInfo> result = userInfoService.findAll();
        return result;
    }

    @PutMapping("/update")
    public String updateUser(@RequestBody UserInfo userInfo) {
        userInfoService.updateUser(userInfo);
        return "修改成功";
    }

    @DeleteMapping("/delete")
    public String deletUser(@RequestParam Integer id) {
        userInfoService.deleteUser(id);
        return "删除成功";
    }

    @PostMapping("/add")
    public String add(@RequestBody UserInfo userInfo) {
        userInfoService.add(userInfo);
        System.out.println(userInfo);
        return "添加成功";
    }

}

我这里只暴露了配置和接口，细节上就是CURD的简单接口实现，不必关注，知道调通了就行

服务调用者环境准备

1，导入所需依赖

  <!-- restTemplate 远程调用 -->
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.5</version>
        </dependency>

2，application.yml

server:
  port: 9013

3，编写RestTemplateConfig

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
import org.springframework.web.client.RestTemplate;

/**
 * @author: myqxin
 * @Desc:
 * @create: 2021-08-20 16:22
 **/
@Configuration
public class RestTemplateConfig {

    @Bean
    public RestTemplate restTemplate() {
        HttpComponentsClientHttpRequestFactory httpRequestFactory = new HttpComponentsClientHttpRequestFactory();
        httpRequestFactory.setConnectionRequestTimeout(30 * 1000);
        httpRequestFactory.setConnectTimeout(30 * 3000);
        httpRequestFactory.setReadTimeout(30 * 3000);
        return new RestTemplate(httpRequestFactory);
    }

}

代码示例及效果

1，服务调用者接口示例

import com.myqxin.pojo.UserInfo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;


/**
 * @author: myqxin
 * @Desc:
 * @create: 2021-08-19 17:29
 **/
@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private RestTemplate restTemplate;

    /**
     * 参数
     * @return
     */
    @GetMapping("/test005")
    public String params() {
        Integer id = 3;
        ResponseEntity<String> exchange = this.restTemplate.exchange(String.format("http://localhost:9005/user/params/%s",id), HttpMethod.GET, null, String.class);
        int statusCodeValue = exchange.getStatusCodeValue();
        String body = exchange.getBody();
        System.out.println(statusCodeValue);
        System.out.println(body);
        return "myqxin";
    }

    /**
     * 添加
     * @return
     */
    @GetMapping("/test004")
    public String add() {
        UserInfo userInfo = new UserInfo();
        userInfo.setUsername("myqxin");
        userInfo.setPassword("1234");
        userInfo.setAge(20);
        HttpEntity httpEntity = new HttpEntity(userInfo);
        ResponseEntity<String> exchange = this.restTemplate.exchange("http://localhost:9005/user/add", HttpMethod.POST, httpEntity, String.class);
        int statusCodeValue = exchange.getStatusCodeValue();
        String body = exchange.getBody();
        System.out.println(statusCodeValue);
        System.out.println(body);
        return "myqxin";
    }

    /**
     * 删除
     * @return
     */
    @GetMapping("/test003")
    public String delete() {
        Integer id = 4;
        ResponseEntity<String> exchange = this.restTemplate.exchange("http://localhost:9005/user/delete?id="+id, HttpMethod.DELETE, null, String.class);
        int statusCodeValue = exchange.getStatusCodeValue();
        String body = exchange.getBody();
        System.out.println(statusCodeValue);
        System.out.println(body);
        return "myqxin";
    }

    /**
     * 修改
     * @return
     * @throws Exception
     */
    @GetMapping("/test002")
    public String update() throws Exception {
        UserInfo userInfo = new UserInfo();
        userInfo.setId(4);
        userInfo.setUsername("myqxin");
        userInfo.setPassword("123456");
        userInfo.setAge(18);
        HttpEntity httpEntity = new HttpEntity(userInfo);
        ResponseEntity<String> exchange = this.restTemplate.exchange("http://localhost:9005/user/update", HttpMethod.PUT, httpEntity, String.class);
        int statusCodeValue = exchange.getStatusCodeValue();
        String body = exchange.getBody();
        System.out.println(statusCodeValue);
        System.out.println(body);
        return "myqxin";
    }

    /**
     * 查询
     * @return
     */
    @GetMapping("/test001")
    public String get() {
        /**
         * url: 请求地址；
         * method: 请求类型(如：POST,PUT,DELETE,GET)；
         * requestEntity: 请求实体，封装请求头，请求内容
         * responseType: 响应类型，根据服务接口的返回类型决定
         * uriVariables: url中参数变量值
         */
        ResponseEntity<String> exchange = this.restTemplate.exchange("http://localhost:9005/user/get", HttpMethod.GET, null, String.class);
        int statusCodeValue = exchange.getStatusCodeValue();
        String body = exchange.getBody();
        System.out.println(statusCodeValue);
        System.out.println(body);
        return "myqxin";
    }

}

请求：http://localhost:9013/user/test004 发送POST请求，添加用户

请求：http://localhost:9013/user/test002 发送PUT请求，修改用户

请求：http://localhost:9013/user/test001 发送GET请求，查询用户

请求：http://localhost:9013/user/test003 发送DELETE请求，删除用户，参数以@RequestParam方式传递

请求：http://localhost:9013/user/test005 发送GET请求，参数以@PathVariable方式传递