SpringCloud-----Feign使用及相关配置

1、Feign是个什么东西？
Feign是微服务调用端的便捷技术。

要说它是什么？我们就要讲到它的作用了。

大家都知道，Ribbon也是微服务调用端的技术，既然有Ribbon技术了，为什么还要用Feign技术呐？

因为Feign是站在巨人Ribbon的肩膀上的成功者。

它成功的整合了Ribbon，是客户端调用从Rest调用变成了接口调用。

接口调用，那就相当简单了。

例如：Ribbon的微服务调用代码如下：

@Resource
	private RestTemplate restTemplate;

@GetMapping("/get")
	public Object getDept(long id){
		
		return this.restTemplate.exchange(DEPT_GET_URL+id, HttpMethod.GET, new HttpEntity(headers), Dept.class);
	}

其中，rest调用微服务代码其实多了就很繁冗了。于是就有了Feign

Feign代码如下：

@Resource
	private IDeptClientService deptClientService;

	@GetMapping("/get")
	public Object getDept(long id){
		
		
		return deptClientService.get(id);
	}

@FeignClient(value="DEPT-8001", configuration=FeignClientConfig.class)
public interface IDeptClientService {

	@GetMapping(value="/dept/get/{id}")
	public Dept get(@PathVariable("id") Long id);
}

知其然顾知其所以然。

2、新建Feign工程

依赖包、feign依赖包中包含了Ribbon包，毕竟是站在巨人的肩膀上出生的嘛

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

FeignClientConfig.java安全配置

package com.zemel.common;

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

import feign.auth.BasicAuthRequestInterceptor;

@Configuration
public class FeignClientConfig {

	@Bean
	public BasicAuthRequestInterceptor getBasicAuthRequestInterceptor(){
		return new BasicAuthRequestInterceptor("wendy", "wendy");
	}
}

4、Feign的重点配置接口

package com.zemel.service;

import java.util.List;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;

import com.zemel.common.FeignClientConfig;
import com.zemel.vo.Dept;

@FeignClient(value="DEPT-8001", configuration=FeignClientConfig.class)
public interface IDeptClientService {

	@GetMapping(value="/dept/get/{id}")
	public Dept get(@PathVariable("id") Long id);
	
	@GetMapping(value="/dept/list")
	public List<Dept> list();
	
	@PostMapping(value="/dept/add")
	public boolean add(Dept dept);
	
}

5、application.yml

eureka:
  client:
    register-with-eureka: false # 不注册
    serviceUrl:
      defaultZone: http://admin:admin@eurekaserver-7001.com:7001/eureka,http://admin:admin@eurekaserver-7002.com:7002/eureka,http://admin:admin@eurekaserver-7003.com:7003/eureka

6、Feign调用

package com.zemel.consumer.controller;

import javax.annotation.Resource;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.zemel.service.IDeptClientService;
import com.zemel.vo.Dept;

@RestController
@RequestMapping("/consumer/dept")
public class DeptController {
	
	@Resource
	private IDeptClientService deptClientService;

	@GetMapping("/get")
	public Object getDept(long id){
		
		
		return deptClientService.get(id);
	}
	
	@GetMapping("/list")
	public Object list(){
		return deptClientService.list();
	}
	
	@GetMapping("/add")
	public Object add(Dept dept){
		return deptClientService.add(dept);
	}
}

7、App.java启动类

package com.zemel.consumer;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;

/**
 * Hello world!
 *
 */
@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients(basePackages={"com.zemel.service"})
public class FeignApp {
	public static void main(String[] args) {
		SpringApplication.run(FeignApp.class, args);
	}
	
	
}

8、Feign压缩配置

我们知道，Rest服务的核心本质是：数据的传输（包括Json、xml等），

那么假如传输数据过大的话，会导致访问过慢，所以需要配置一个压缩机制。

application.yml

server:
  port: 80

logging:
  level:
    com.zemel.service: DEBUG

eureka:
  client:
    register-with-eureka: false # 不注册
    serviceUrl:
      defaultZone: http://admin:admin@eurekaserver-7001.com:7001/eureka,http://admin:admin@eurekaserver-7002.com:7002/eureka,http://admin:admin@eurekaserver-7003.com:7003/eureka

feign:
  compression:
    request:
      mime-types: # 压缩类型
      - text/xml
      - application/xml
      - application/json
      min-request-size: 2048 #超过2048字节进行压缩
      

9、配置日志输出

其中8当中已经配置了日志输出，feign的程序日志输出如下：

package com.zemel.consumer.config;

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

import feign.auth.BasicAuthRequestInterceptor;

@Configuration
public class FeignClientConfig {
	
    // 所有日志输出
	@Bean
	public feign.Logger.Level getFeignLoggerLevel(){
		return feign.Logger.Level.FULL;
	}

	@Bean
	public BasicAuthRequestInterceptor getBasicAuthRequestInterceptor(){
		return new BasicAuthRequestInterceptor("wendy", "wendy");
	}
}

总结：Feign=RestTemplate + HttpHeader + Ribbon + Eureka综合题 = 业务接口的自动实例化