一、整合feign

第一步：给三个模块引入依赖

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

第二步：在启动类上加上@EnableFeignClients
第三步：编写代码

package com.badcat.a.feignClient;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;

/**
 * @author 50244
 */
@FeignClient(name = "b")
public interface BFeignClinet {

    @GetMapping("/hello/say_hello")
    String sayHello();
}

package com.badcat.a.controller;

import com.badcat.a.feignClient.BFeignClinet;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import java.util.List;

/**
 * @author 50244
 */
@Slf4j
@RestController
@RequestMapping("/feign")
public class TestFeignController {

    @Autowired
    private BFeignClinet bFeignClinet;

    @GetMapping("/let_module-b_say_hello")
    public String letModuleBSayHello(){

        String result = this.bFeignClinet.sayHello();

        log.info("module-b say : [{}]", result);
        return String.format("module-b say : [%s]", result);
    }
}

调用结果，完美兼容ribbon组件：

二、feign的日志级别

下面使用全局配置的方式将日志级别修改为full

前提：需要先将feign接口所在的包的日志级别修改为debug

logging:
  level:
    ## 设置feign接口的日志级别为debug
    com.badcat.a.feignClient: debug

方式一：Java代码

package com.badcat.a.config.feign;

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

public class FeignConfiguration {

    @Bean
    public Logger.Level level(){
        return Logger.Level.FULL;
    }
}

修改启动文件的注解：@EnableFeignClients(defaultConfiguration = FeignConfiguration.class)

package com.badcat.a;

import com.badcat.a.config.feign.FeignConfiguration;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

/**
 * @author 50244
 */
@SpringBootApplication
@EnableFeignClients(defaultConfiguration = FeignConfiguration.class)
public class AApplication {
    public static void main(String[] args) {
        SpringApplication.run(AApplication.class, args);
    }

    @Bean
    @LoadBalanced
    public RestTemplate restTemplate(){
        return new RestTemplate();
    }
}

调用结果，调用module-b、module-c都呈现full级别日志：

方式二：配置文件方式

回退上面Java方式的代码，添加如下配置

feign:
  client:
    config:
      default:
        loggerLevel: full

调用结果，调用module-b、module-c都呈现full级别日志：

三、细粒度控制feign日志级别

下面修改日志级别，调用module-b的日志级别是full，调用module-c的日志级别是basic

前提：需要先将feign接口所在的包的日志级别修改为debug

logging:
  level:
    ## 设置feign接口的日志级别为debug
    com.badcat.a.feignClient: debug

方式一：Java代码：

注意：@Configuration的问题同上一章ribbon类似。

package com.badcat.a.config.feign;

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

public class BFeignConfiguration {

    @Bean
    public Logger.Level level(){
        return Logger.Level.FULL;
    }
}

package com.badcat.a.feignClient;

import com.badcat.a.config.feign.BFeignConfiguration;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;

/**
 * @author 50244
 */
@FeignClient(name = "b", configuration = BFeignConfiguration.class)
//@FeignClient(name = "b")
public interface BFeignClinet {

    @GetMapping("/hello/say_hello")
    String sayHello();
}

package com.badcat.a.config.feign;

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

public class CFeignConfiguration {

    @Bean
    public Logger.Level level(){
        return Logger.Level.BASIC;
    }
}

package com.badcat.a.feignClient;

import com.badcat.a.config.feign.BFeignConfiguration;
import com.badcat.a.config.feign.CFeignConfiguration;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;

/**
 * @author 50244
 */
@FeignClient(name = "c", configuration = CFeignConfiguration.class)
//@FeignClient(name = "c")
public interface CFeignClinet {

    @GetMapping("/hello/say_hello")
    String sayHello();
}

调用结果，调用module-b呈现full级别日志，调用module-c呈现basic基本别日志：

方式二：配置文件方式

先将Java方式的代码还原，在配置文件中添加如下配置：

feign:
  client:
    config:
      b:
        loggerLevel: full
      c:
        loggerLevel: basic

调用结果，调用module-b呈现full级别日志，调用module-c呈现basic基本别日志：

四、feign支持的配置项

五、对象类参数的处理方式

例如对于这样的接口，feign该如何写呢？

public User getOne(User user);

如果是get请求，需要在参数前添加@SpringQueryMap，例如：

@FeignClient("user")
public interface UserFeignClient {
  @GetMapping("/get_one")
  public User getOne(@SpringQueryMap User user);
}

如果是get请求，需要在参数前添加@RequestBody，例如：

@FeignClient("user")
public interface UserFeignClient {
  @PostMapping("/get_one")
  public User getOne(@RequestBody User user);
}

六、使用连接池

方式一：httpclient

引入依赖

        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-httpclient</artifactId>
        </dependency>

添加配置

feign:
  httpclient:
    enabled: true
    # feign的最大连接数
    max-connections: 200
    # feign单个路径的最大连接数
    max-connections-per-route: 50

方式二：okhttp

引入依赖

        <dependency>
            <groupId>io.github.openfeign</groupId>
            <artifactId>feign-okhttp</artifactId>
            <version>11.8</version>
        </dependency>

添加配置

feign:
  httpclient:
    # enabled: true
    # feign的最大连接数
    max-connections: 200
    # feign单个路径的最大连接数
    max-connections-per-route: 50
  okhttp:
    enabled: true

这部分代码放到了码云 study_badcat/spring-cloud-alibaba-study (gitee.com)
，v4.0分支