开发环境：IntelliJ IDEA 2019.2.2
Spring Boot版本：2.1.8
一、发布REST服务
1、IDEA新建一个名称为rest-server的Spring Boot项目
2、新建一个实体类User.java
package com.example.restserver.domain;
public class User {
String name;
Integer age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
}
3、新建一个控制器类 UserController.java
package com.example.restserver.web;
import com.example.restserver.domain.User;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class UserController {
@RequestMapping(value="/user/{name}", produces = MediaType.APPLICATION_JSON_VALUE)
public User user(@PathVariable String name) {
User u = new User();
u.setName(name);
u.setAge(30);
return u;
}
}
项目结构如下：
访问http://localhost:8080/user/lc，页面显示：
{"name":"lc","age":30}
二、使用RestTemplae调用服务
1、IDEA新建一个名称为rest-client的Spring Boot项目
2、新建一个含有main方法的普通类RestTemplateMain.java，调用服务
package com.example.restclient;
import com.example.restclient.domain.User;
import org.springframework.web.client.RestTemplate;
public class RestTemplateMain {
public static void main(String[] args){
RestTemplate tpl = new RestTemplate();
User u = tpl.getForObject("http://localhost:8080/user/lc", User.class);
System.out.println(u.getName() + "," + u.getAge());
}
}
右键Run 'RestTemplateMain.main()'，控制台输出：lc,30
3、在bean里面使用RestTemplate，可使用RestTemplateBuilder，新建类UserService.java
package com.example.restclient.service;
import com.example.restclient.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
@Service
public class UserService {
@Autowired
private RestTemplateBuilder builder;
@Bean
public RestTemplate restTemplate(){
return builder.rootUri("http://localhost:8080").build();
}
public User userBuilder(String name){
User u = restTemplate().getForObject("/user/" + name, User.class);
return u;
}
}
4、编写一个单元测试类，来测试上面的UserService的bean。
package com.example.restclient.service;
import com.example.restclient.domain.User;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
@RunWith(SpringRunner.class)
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.NONE)
public class UserServiceTest {
@Autowired
private UserService userService;
@Test
public void testUser(){
User u = userService.userBuilder("lc");
Assert.assertEquals("lc", u.getName());
}
}
5、控制器类UserController.cs 中调用
配置在application.properties 配置端口和8080不一样，如server.port = 9001
@Autowired
private UserService userService;
@RequestMapping(value="/user/{name}", produces = MediaType.APPLICATION_JSON_VALUE)
public User user(@PathVariable String name) {
User u = userService.userBuilder(name);
return u;
}
三、使用Feign调用服务
继续在rest-client项目基础上修改代码。
1、pom.xml添加依赖
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-core</artifactId>
<version>9.5.0</version>
</dependency>
<dependency>
<groupId>io.github.openfeign</groupId>
<artifactId>feign-gson</artifactId>
<version>9.5.0</version>
</dependency>
2、新建接口UserClient.java
package com.example.restclient.service;
import com.example.restclient.domain.User;
import feign.Param;
import feign.RequestLine;
public interface UserClient {
@RequestLine("GET /user/{name}")
User getUser(@Param("name")String name);
}
3、在控制器类UserController.java 中调用
decoder(new GsonDecoder()) 表示添加了解码器的配置，GsonDecoder会将返回的JSON字符串转换为接口方法返回的对象。
相反的，encoder(new GsonEncoder())则是编码器，将对象转换为JSON字符串。
@RequestMapping(value="/user2/{name}", produces = MediaType.APPLICATION_JSON_VALUE)
public User user2(@PathVariable String name) {
UserClient service = Feign.builder().decoder(new GsonDecoder())
.target(UserClient.class, "http://localhost:8080/");
User u = service.getUser(name);
return u;
}
4、优化第3步代码，并把请求地址放到配置文件中。
（1）application.properties 添加配置
（2）新建配置类ClientConfig.java
package com.example.restclient.config;
import com.example.restclient.service.UserClient;
import feign.Feign;
import feign.gson.GsonDecoder;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class ClientConfig {
@Value("${application.client.url}")
private String clientUrl;
@Bean
UserClient userClient(){
UserClient client = Feign.builder()
.decoder(new GsonDecoder())
.target(UserClient.class, clientUrl);
return client;
}
}
（3）控制器 UserController.java 中调用
@Autowired
private UserClient userClient;
@RequestMapping(value="/user3/{name}", produces = MediaType.APPLICATION_JSON_VALUE)
public User user3(@PathVariable String name) {
User u = userClient.getUser(name);
return u;
}
UserController.java最终内容：
package com.example.restclient.web;
import com.example.restclient.domain.User;
import com.example.restclient.service.UserClient;
import com.example.restclient.service.UserService;
import feign.Feign;
import feign.gson.GsonDecoder;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.MediaType;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class UserController {
@Autowired
private UserService userService;
@Autowired
private UserClient userClient;
@RequestMapping(value="/user/{name}", produces = MediaType.APPLICATION_JSON_VALUE)
public User user(@PathVariable String name) {
User u = userService.userBuilder(name);
return u;
}
@RequestMapping(value="/user2/{name}", produces = MediaType.APPLICATION_JSON_VALUE)
public User user2(@PathVariable String name) {
UserClient service = Feign.builder().decoder(new GsonDecoder())
.target(UserClient.class, "http://localhost:8080/");
User u = service.getUser(name);
return u;
}
@RequestMapping(value="/user3/{name}", produces = MediaType.APPLICATION_JSON_VALUE)
public User user3(@PathVariable String name) {
User u = userClient.getUser(name);
return u;
}
}
项目结构
先后访问下面地址，可见到输出正常结果
http://localhost:9001/user/lc
http://localhost:9001/user2/lc2
http://localhost:9001/user3/lc3
