【SpringCloud构建微服务系列】Feign的使用详解

一、简介

在微服务中，服务消费者需要请求服务生产者的接口进行消费，可以使用SpringBoot自带的RestTemplate或者HttpClient实现，但是都过于麻烦。

这时，就可以使用Feign了，它可以帮助我们更加便捷、优雅地调用HTTP API。

本文代码全部已上传至我的github，点击这里获取。

二、为服务消费者整合Feign

1.复制项目microservice-consumer-movie，并修改为microservice-consumer-movie-feign

2.pom文件添加依赖：

 　　　　<dependency>
             <groupId>org.springframework.cloud</groupId>
             <artifactId>spring-cloud-starter-feign</artifactId>
         </dependency>

3.创建一个Feign接口，并添加@FeignClient注解

 package cn.sp.client;

 import cn.sp.bean.User;
 import org.springframework.cloud.netflix.feign.FeignClient;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;

 /**
  * @author ship
  * @Description
  * @Date: 2018-07-17 13:25
  */
 @FeignClient(name = "microservice-provider-user")
 public interface UserFeignClient {

     @GetMapping("/{id}")
     User findById(@PathVariable("id") Long id);
 }

@FeignClient注解中的microservice-provider-user是一个任意的客户端名称，用于创建Ribbon负载均衡器。

再这里，由于使用了Eureka，所以Ribbon会把microservice-provider-user解析为Eureka Server服务注册表中的服务。

4.Controller层代码

 /**
  * 请求用户微服务的API
  * Created by 2YSP on 2018/7/8.
  */
 @RestController
 public class MovieController {

     @Autowired
     private UserFeignClient userFeignClient;

     @GetMapping("/user/{id}")
     public User findById(@PathVariable Long id){
         return userFeignClient.findById(id);
     }
 }

5.修改启动类，添加@EnableFeignClients注解

 /**
  * 使用Feign进行声明式的REST Full API调用
  */
 @EnableFeignClients(basePackages = {"cn.sp.client"})
 @EnableEurekaClient
 @SpringBootApplication
 public class MicroserviceConsumerMovieFeignApplication {

     public static void main(String[] args) {
         SpringApplication.run(MicroserviceConsumerMovieFeignApplication.class, args);
     }
 }

这里我添加了basePackages属性指定扫描的包，开始没添加报错了。

这样，电影微服务就可以调用用户微服务的API了。

1.启动microservice-discovery-eureka 

2.启动生产者microservice-provider-user

3.启动microservice-consumer-movie-feign

4.访问http://localhost:8010/user/1获得返回数据。

三、手动创建Feign

1.复制microservice-provider-user并修改artifactId为microservice-provider-user-with-auth

2.添加依赖

 <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-security</artifactId>
  </dependency>

3.代码部分

 package cn.sp.conf;

 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
 import org.springframework.security.config.annotation.method.configuration.EnableGlobalMethodSecurity;
 import org.springframework.security.config.annotation.web.builders.HttpSecurity;
 import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
 import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
 import org.springframework.security.core.GrantedAuthority;
 import org.springframework.security.core.authority.SimpleGrantedAuthority;
 import org.springframework.security.core.userdetails.UserDetails;
 import org.springframework.security.core.userdetails.UserDetailsService;
 import org.springframework.security.core.userdetails.UsernameNotFoundException;
 import org.springframework.security.crypto.password.NoOpPasswordEncoder;
 import org.springframework.security.crypto.password.PasswordEncoder;
 import org.springframework.stereotype.Component;

 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;

 /**
  * @author ship
  * @Description
  * @Date: 2018-07-18 09:51
  */
 @Configuration
 @EnableWebSecurity
 @EnableGlobalMethodSecurity(prePostEnabled = true)
 public class WebSecurityConfig extends WebSecurityConfigurerAdapter{

     @Autowired
     CustomUserDetailService userDetailService;

     @Override
     protected void configure(AuthenticationManagerBuilder auth) throws Exception {
         super.configure(auth);
         auth.userDetailsService(userDetailService).passwordEncoder(this.passwordEncoder());
     }

     @Override
     protected void configure(HttpSecurity http) throws Exception {
         super.configure(http);
         //所有请求都需要经过HTTP basic认证
         http.authorizeRequests().anyRequest().authenticated().and().httpBasic();
     }

     @Bean
     public PasswordEncoder passwordEncoder(){
         //明文编码器，这是一个不做任何操作的密码编码器，是Spring提供给我们做明文测试的
         return NoOpPasswordEncoder.getInstance();
     }

 }

 @Component
 class CustomUserDetailService implements UserDetailsService{
     /**
      * 模拟两个账号：用户名user和用户名admin
      * @param username
      * @return
      * @throws UsernameNotFoundException
      */
     @Override
     public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
         if ("user".equals(username)){
             return new SecurityUser("user","password1","user-role");
         }else if ("admin".equals(username)){
             return new SecurityUser("admin","password2","admin-role");
         }
         return null;
     }
 }

 class SecurityUser implements UserDetails{

     private Long id;
     private String username;
     private String password;
     private String role;

     public SecurityUser(String username,String password,String role){
         this.username = username;
         this.password = password;
         this.role = role;
     }

     public Long getId() {
         return id;
     }

     public void setId(Long id) {
         this.id = id;
     }

     public void setUsername(String username) {
         this.username = username;
     }

     public void setPassword(String password) {
         this.password = password;
     }

     public String getRole() {
         return role;
     }

     public void setRole(String role) {
         this.role = role;
     }

     @Override
     public Collection<? extends GrantedAuthority> getAuthorities() {
         List<GrantedAuthority> authorities = new ArrayList<>();
         SimpleGrantedAuthority authority = new SimpleGrantedAuthority(this.role);
         authorities.add(authority);
         return authorities;
     }

     @Override
     public String getPassword() {
         return this.password;
     }

     @Override
     public String getUsername() {
         return this.username;
     }

     @Override
     public boolean isAccountNonExpired() {
         return true;
     }

     @Override
     public boolean isAccountNonLocked() {
         return true;
     }

     @Override
     public boolean isCredentialsNonExpired() {
         return true;
     }

     @Override
     public boolean isEnabled() {
         return true;
     }
 }

 package cn.sp.controller;

 import cn.sp.bean.User;
 import cn.sp.service.UserService;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.security.core.GrantedAuthority;
 import org.springframework.security.core.context.SecurityContextHolder;
 import org.springframework.security.core.userdetails.UserDetails;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RestController;

 import java.util.Collection;

 /**
  * Created by 2YSP on 2018/7/8.
  */
 @RestController
 public class UserController {

     @Autowired
     private UserService userService;

     private static final Logger log = LoggerFactory.getLogger(UserController.class);

     @GetMapping("/{id}")
     public User findById(@PathVariable Long id){
         Object principal = SecurityContextHolder.getContext().getAuthentication().getPrincipal();
         if (principal instanceof UserDetails){
             UserDetails user = (UserDetails) principal;
             Collection<? extends GrantedAuthority> authorities = user.getAuthorities();
             for (GrantedAuthority g : authorities){
                 //打印用户当前信息
                 log.info("当前用户是:{},角色是:{}",user.getUsername(),g.getAuthority());
             }
         }else {
             //do other things
         }
         return userService.findById(id);
     }
 }

4.测试修改后的用户服务

先启动microservice-discovery-eureka，再启动microservice-provider-user-with-auth，访问http://localhost:8000/1，即可弹出一个登录框，输入用户名和密码（user/password1和admin/password）才能获取结果。

5.修改电影服务，复制microservice-consumer-movie-feign并改为microservice-consumer-movie-feign-manual

6.去掉Feign接口的@FeignClient注解，去掉启动类的@EnableFeignClients注解

7.controller层代码修改如下。

/**
 * 请求用户微服务的API
 * Created by 2YSP on 2018/7/8.
 */
@Import(FeignClientsConfiguration.class)
@RestController
public class MovieController {

    private UserFeignClient userUserFeignClient;

    private UserFeignClient adminUserFeignClient;

    @Autowired
    public MovieController(Decoder decoder, Encoder encoder, Client client, Contract contract){
        this.userUserFeignClient = Feign.builder().client(client).decoder(decoder).encoder(encoder)
                .contract(contract).requestInterceptor(new BasicAuthRequestInterceptor("user","password1"))
                .target(UserFeignClient.class,"http://microservice-provider-user/");

        this.adminUserFeignClient = Feign.builder().client(client).decoder(decoder).encoder(encoder)
                .contract(contract).requestInterceptor(new BasicAuthRequestInterceptor("admin","password2"))
                .target(UserFeignClient.class,"http://microservice-provider-user/");
    }

    @GetMapping("/user-user/{id}")
    public User findByIdUser(@PathVariable Long id){
        return userUserFeignClient.findById(id);
    }

    @GetMapping("/user-admin/{id}")
    public User findByIdAdmin(@PathVariable Long id){
        return adminUserFeignClient.findById(id);
    }
}

8.启动microservice-consumer-movie-feign-manual，并访问http://localhost:8010/user-user/4获取结果同时看到用户微服务打印日志。

-- ::06.320  INFO  --- [nio--exec-] cn.sp.controller.UserController          : 当前用户是:user,角色是:user-role

访问http://localhost:8010/user-admin/4打印日志：

-- ::13.772  INFO  --- [nio--exec-] cn.sp.controller.UserController          : 当前用户是:admin,角色是:admin-role

四、Feign对继承的支持

Feign还支持继承，将一些公共操作弄到父接口，从而简化开发

比如，先写一个基础接口：UserService.java

 public interface UserService {
     @RequestMapping(method= RequestMethod.GET,value="/user/{id}")
     User getUser(@PathVariable("id") long id);
 }

服务提供者Controller：UserResource.java

 @RestController
 public class UserResource implements UserService {

   //...
 }

服务消费者：UserClient.java

 @FeignClient("users")
 public interface UserClient extends UserService {
 }

虽然很方便但是官方不建议这样做。

五、Feign对压缩的支持

Feign还可以对传输的数据进行压缩，只需要在appllication.properties文件添加如下配置即可。

feign.compression.request.enable=true
feign.compression.response.enable=true
feign.compression.request.mime-types=text/xml,application/xml,application/json
feign.compression.request.min-request-size=2048

六、设置Feign的日志

1.复制项目microservice-consumer-movie-feign，修改为microservice-consumer-movie-feign-logging

2.编写Feign配置类

 package cn.sp.conf;

 import feign.Logger;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;

 /**
  * Created by 2YSP on 2018/7/18.
  */
 @Configuration
 public class FeignLogConfiguration {

     /**
      * NONE:不记录任何日志（默认）
      * BASIC：仅记录请求方法、URL、响应状态代码以及执行时间
      * HEADERS：记录BASIC级别的基础上，记录请求和响应的header
      * FULL:记录请求和响应的header，body和元数据
      * @return
      */
     @Bean
     Logger.Level feignLoggerLevel(){
         return Logger.Level.FULL;
     }
 }

3.修改Feign，使用指定配置类

 @FeignClient(name = "microservice-provider-user",configuration = FeignLogConfiguration.class)
 public interface UserFeignClient {

     @GetMapping("/{id}")
     User findById(@PathVariable("id") Long id);
 }

4.在application.yml中添加如下内容，设置日志级别，注意：Feign的日志打印只会对DEBUG级别做出响应

5测试：启动microservice-discovery-eureka，microservice-provider-user和microservice-consumer-movie-feign-logging，访问http://localhost:8010/user/1，可看到日志结果。

七、使用Feign构造多参数请求

当我们用Get请求多参数的URL的时候，比如：http://microservice-provider-user/get?id=1&username=zhangsan，可能会采取如下的方式

 @FeignClient(name = "microservice-provider-user")
 public interface UserFeignClient {

     @RequestMapping(value = "/get",method = RequestMethod.GET)
     User get0(User user);

 }

然而会报错，尽管指定了GET方法，Feign仍然会使用POST方法发起请求。

正确处理方式一：使用@RequestParam注解

  @RequestMapping(value = "/get",method = RequestMethod.GET)
  User get1(@RequestParam("id") Long id,@RequestParam("username") String username);

但是这种方法也有个缺点，如果参数比较多就要写很长的参数列表。

正确处理方式二：使用map接收

 @RequestMapping(value = "/get",method = RequestMethod.GET)
 User get2(Map<String,Object> map);

处理方式三：如果请求方式没有限制的话，换成POST方式

  @RequestMapping(value = "/get",method = RequestMethod.POST)
  User get3(User user);

排版比较乱敬请见谅，参考资料：SpringCloud与Docker微服务架构实战。