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SpringCloud之Feign

【 前面的话 】书接上文，本文的某些知识依赖我的第一篇SpringCLoud的文章： SpringCloud之Eureka ，如果没有看过可以先移步去看一下。另外在微服务架构中，业务都会被拆分成一个个独立的服务，服务与服务的通讯是基于http restful的。Spring cloud有两种服务调用方式，一种是ribbon+restTemplate，另一种是feign。上一篇文章已经讲过 ribbon+rest 这种方式了，这一片博文主要讲feign的应用。

壹、Feign的简介

Feign是一个声明式的伪Http客户端，它使得写Http客户端变得更简单。使用Feign，只需要创建一个接口并注解。它具有可插拔的注解特性，可使用Feign 注解和JAX-RS注解。Feign支持可插拔的编码器和解码器。Feign默认集成了Ribbon，并和Eureka结合，默认实现了负载均衡的效果。

简而言之：

Feign 采用的是基于接口的注解
Feign 整合了ribbon

贰、准备工作

新建一个feign子工程 lovin-feign-client ，用于后面的操作。下面是主要的pom依赖:

<parent>
        <artifactId>lovincloud</artifactId>
        <groupId>com.eelve.lovincloud</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>lovin-feign-client</artifactId>
    <version>0.0.1</version>
    <name>lovinfeignclient</name>
    <description>feignclient测试</description>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-hystrix</artifactId>
            <version>1.4.7.RELEASE</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

这里为了安全，我这里还是添加 spring-boot-starter-security

server:
  port: 8806   # 服务端口号
spring:
  application:
    name: lovinfeignclient     # 服务名称
  security:
    basic:
      enabled: true
    user:
      name: lovin
      password: ${REGISTRY_SERVER_PASSWORD:lovin}
eureka:
  client:
    serviceUrl:
      defaultZone: http://lovin:lovin@localhost:8881/eureka/   # 注册到的eureka服务地址
feign:
  hystrix:
    enabled: true

配置 spring-boot-starter-security ，这里为了方便我这里放开所有请求

package com.eelve.lovin.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;

/**
 * @ClassName SecurityConfig
 * @Description TDO
 * @Author zhao.zhilue
 * @Date 2019/8/16 14:13
 * @Version 1.0
 **/
@Configuration
public class WebSecurityConfig extends WebSecurityConfigurerAdapter {

    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.authorizeRequests().anyRequest().permitAll()
                .and().csrf().disable();
    }
}

在主类上添加 @EnableFeignClients 和 @EnableHystrix ，当然也需要注册到注册中心：

package com.eelve.lovin;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.cloud.openfeign.EnableFeignClients;

/**
 * @ClassName LovinFeignClientApplication
 * @Description TDO
 * @Author zhao.zhilue
 * @Date 2019/8/15 17:17
 * @Version 1.0
 **/
@SpringBootApplication
@EnableFeignClients
@EnableDiscoveryClient
@EnableHystrix
public class LovinFeignClientApplication {
    public static void main(String[] args) {
        SpringApplication.run(LovinFeignClientApplication.class,args);
    }
}

添加一个远程调用的服务端 FeignRemoteService ，并且配置feign调用信息：

package com.eelve.lovin.service;

import com.eelve.lovin.hystrix.FeignRemoteServiceImpl;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

/**
 * @ClassName FeignRemoteService
 * @Description TDO
 * @Author zhao.zhilue
 * @Date 2019/8/15 17:18
 * @Version 1.0
 **/
@FeignClient(value = "lovineurkaclient",fallback = FeignRemoteServiceImpl.class)
public interface FeignRemoteService {

    @RequestMapping(value = "/hello",method = RequestMethod.GET)
    public String hello();
}

添加熔断器调用方法：新建 FeignRemoteServiceImpl 实现 FeignRemoteService 接口：

package com.eelve.lovin.hystrix;

import com.eelve.lovin.service.FeignRemoteService;
import org.springframework.stereotype.Component;

/**
 * @ClassName FeignRemoteServiceImpl
 * @Description TDO
 * @Author zhao.zhilue
 * @Date 2019/8/15 17:31
 * @Version 1.0
 **/
@Component
public class FeignRemoteServiceImpl implements FeignRemoteService {
    @Override
    public String hello() {
        return "hystrix起作用了";
    }
}

最后新建 FeignController ，来消费服务：

package com.eelve.lovin.controller;

import com.eelve.lovin.service.FeignRemoteService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

/**
 * @ClassName FeignController
 * @Description TDO
 * @Author zhao.zhilue
 * @Date 2019/8/15 17:21
 * @Version 1.0
 **/
@RestController
public class FeignController {

    @Autowired
    FeignRemoteService feignRemoteService;

    @GetMapping(value = "/getHello")
    public String getHello() {
        return feignRemoteService.hello();
    }
}

叁、启动测试

依次启动eureka的服务端和两个客户端，以及新建的lovin-feign-client

SpringCloud之Feign

我们可以看到服务已经全部启动成功

然后访问 http://localhost :8806/getHello

SpringCloud之Feign

我们可以看到已经可以通过feign调到我们建立的eureka客户端了

再次请求接口观察返回

SpringCloud之Feign

我们可以看到我们调到了通过feign调用ribbon负载的另外一个接口了，到这里我们就已经弄好了一个简单的ribbon负载。

肆、添加Hystrix Dashboard断路器监控

添加需要的pom依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId>
    <version>2.1.2.RELEASE</version>
</dependency>

在主类上添加 @EnableHystrixDashboard ，开启断路器监控，并且配置 HystrixMetricsStreamServlet

package com.eelve.lovin;

import com.netflix.hystrix.contrib.metrics.eventstream.HystrixMetricsStreamServlet;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;

/**
 * @ClassName LovinFeignClientApplication
 * @Description TDO
 * @Author zhao.zhilue
 * @Date 2019/8/15 17:17
 * @Version 1.0
 **/
@SpringBootApplication
@EnableFeignClients
@EnableDiscoveryClient
@EnableHystrix
@EnableHystrixDashboard
public class LovinFeignClientApplication {
    public static void main(String[] args) {
        SpringApplication.run(LovinFeignClientApplication.class,args);
    }

    @Bean
    public ServletRegistrationBean getServlet(){
        HystrixMetricsStreamServlet streamServlet = new HystrixMetricsStreamServlet();
        ServletRegistrationBean registrationBean = new ServletRegistrationBean(streamServlet);
        registrationBean.setLoadOnStartup(1);
        registrationBean.addUrlMappings("/actuator/hystrix.stream");
        registrationBean.setName("HystrixMetricsStreamServlet");
        return registrationBean;
    }
}

访问 http://localhost :8806/hystrix

SpringCloud之Feign

这里我们通过首页可以看到：

默认的集群监控：通过URL http://turbine-hostname:port/turbine.stream开启，实现对默认集群的监控。
指定的集群监控：通过URL http://turbine-hostname:port/turbine.stream?cluster=[clusterName]开启，实现对clusterName的监控。
单体应用监控：通过URL http://hystrix-app:port/hystrix.stream开启，实现对某个具体的服务监控