【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。

2018-07-18 14:19:06.320  INFO 14256 --- [nio-8000-exec-1] 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：

2018-07-18 14:20:13.772  INFO 14256 --- [nio-8000-exec-2] 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。