feign的使用，可以簡化服務之間的呼叫，讓服務之間呼叫更加優雅，本文從feign自定義配置和建立feign完成服務之間複雜許可權驗證，來進一步理解和定製feign。

本文示例參考了《Spring Cloud與Docker微服務架構實踐》

自定義配置

• 建立Feign的配置類

@Configuration
public class FeignConfiguration{
     @Bean
     public Contract feignContract(){
         return new feign.Contract.Default();
    }

    @Bean
 

    public BasicAuthRequestInterceptor basicAuthRequestInterceptor(){
         return new BasicAuthRequestInterceptor("user","password");
   }
}

說明：第一個@Bean配置是在FeignClient中的介面中使用Feign自帶的註解； 第二個@Bean配置是在請求介面中要進行基於Http Basic的認證後才能呼叫。

• FeignClient介面引用配置

@FeignClient(name="hello", configuration=FeignConfiguration.class)
public
 
 interface HelloService{
    @RequestLine("GET /message")
    HelloMessage hello();
}

需要注意的是： FeignConfiguration類不能包含在主應用程式上下文的@ComponentScan中，否則該配置會被所有的@FeignClient共享。

Ribbon的自定義配置中也需要注意這個問題。

服務呼叫的複雜許可權認證

上面演示了服務之間可以通過自定義配置完成基於Http Basic的認證，但是不能滿足根據不同的角色不同的使用者執行不同的操作，即服務之間的呼叫有更復雜的許可權要求，就不能滿足要求了，這時候要針對feign做進一步的改進。

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

• 關鍵許可權配置（服務提供者）

package com.example.helloauth.configuration;

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;

/**
 * @author billjiang [email protected]
 * @create 17-8-26
 */
@Configuration
@EnableWebSecurity
@EnableGlobalMethodSecurity(prePostEnabled = true)
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception{
        http.authorizeRequests().anyRequest().authenticated().and().httpBasic();
    }


    @Bean
    public PasswordEncoder passwordEncoder(){
        return NoOpPasswordEncoder.getInstance();
    }

    @Autowired
    private CustomUserDetailService userDetailService;

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

    @Component
    class CustomUserDetailService implements UserDetailsService{
        @Override
        public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException{
            if("user".equals(username)){
                return new SecurityUser("user","123456","user-role");
            }else if("admin".equals(username)){
                return new SecurityUser("admin","123456","admin-role");
            }else{
                return null;
            }
        }
    }

    class SecurityUser implements UserDetails{
        private static final long serialVersionUID=1L;

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

        public SecurityUser(){

        }

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


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

        public Long getId() {
            return id;
        }

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

        @Override
        public String getUsername() {
            return 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;
        }

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

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

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

        public String getRole() {
            return role;
        }

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

}

啟動專案hello-auth後,可以見到頁面需要輸入使用者名稱和密碼才能訪問。

• 服務消費者hello-auth-feign修改
  1）去掉啟動類上的@EnableFeignClients註解
  2）去掉介面的@FeignClient的註解

package com.example.helloauthconsumerfeign.service;

import com.example.helloauthconsumerfeign.model.User;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

/**
 * @author billjiang [email protected]
 * @create 17-8-23
 */
//@FeignClient(value="hello-auth")
public interface HelloAuthService {

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


}

3）編寫Controller類如下

package com.example.helloauthconsumerfeign.controller;

import com.example.helloauthconsumerfeign.model.User;
import com.example.helloauthconsumerfeign.service.HelloAuthService;
import feign.Client;
import feign.Contract;
import feign.Feign;
import feign.auth.BasicAuthRequestInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import feign.codec.Decoder;
import feign.codec.Encoder;
import org.springframework.cloud.netflix.feign.FeignClientsConfiguration;
import org.springframework.context.annotation.Import;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;


/**
 * @author billjiang [email protected]
 * @create 17-8-26
 */
@Import(FeignClientsConfiguration.class)
@RestController
public class HelloAuthFeignController {
    private HelloAuthService userAuthService;

    private HelloAuthService adminAuthService;

    @Autowired
    public HelloAuthFeignController(Decoder decoder, Encoder encoder, Client client, Contract contract){
        this.userAuthService= Feign.builder().client(client).encoder(encoder).decoder(decoder).contract(contract)
                .requestInterceptor(new BasicAuthRequestInterceptor("user","123456"))
                .target(HelloAuthService.class,"http://hello-auth/");

        this.adminAuthService= Feign.builder().client(client).encoder(encoder).decoder(decoder).contract(contract)
                .requestInterceptor(new BasicAuthRequestInterceptor("admin","123456"))
                .target(HelloAuthService.class,"http://hello-auth/");
    }

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


    @GetMapping("/admin/{id}")
    public User findByIdAdmin(@PathVariable Long id){
        return this.adminAuthService.findById(id);
    }


}

• 消費者呼叫
  在瀏覽器器分別輸入http://localhost:8031/admin/1和http://localhost:8031/user/2則可以完成服務之間授權的呼叫。

在實際業務中會根據不同的角色，執行不同的業務操作，基於以上示例可以在服務之間完成複雜的服務鑑權。