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。

巴特西

【SpringCloud构建微服务系列】Feign的使用详解