feign介绍

feign整合了ribbon和hystrix。除了整合两者的强大功能外，还提供了一种声明式的web服务客户端定义方式。feign简化了ribbon中template的开发，提供更高层次的接口.feign自身也提供了一下可插拔的组件，如编码器和解码器。等等

快速入门

spring-cloud-consumer-01

步骤:

1. 添加feign的依赖

在pom.xml中添加下面的maven配置

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

1. 启动类中添加@EnableFeignClients注解

2. 开发FeignClient程序

详细代码实现

SpringCloudConsumer01Application.java

package com.example.demo;
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;
import org.springframework.cloud.netflix.ribbon.RibbonClient;
import com.example.config.LoadBarentConfig;
@EnableEurekaClient
@SpringBootApplication
@EnableFeignClients
public class SpringCloudConsumer01Application {
    public static void main(String[] args) {
        SpringApplication.run(SpringCloudConsumer01Application.class, args);
    }
}

UserFeignClient.java

package com.example.demo.feign;
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.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import com.example.demo.model.User;
import feign.Param;
@FeignClient("spring-cloud-provider")
public interface UserFeignClient {
    @RequestMapping(value="/user/get?id={id}",method=RequestMethod.GET)
    public User get(@PathVariable("id") String id);
}

UserConstroller.java

package com.example.demo.controller;
@RestController
@RequestMapping(value="/user")
public class UserConstroller {
    @Autowired
    private UserFeignClient userFeignClient;
    @ResponseBody
    @GetMapping("/feign_get")
    public User feign(String id){
        User  u = userFeignClient.get(id);
        return u;
    }
}

服务提供端

spring-cloud-provider-01和spring-cloud-provider-02

这两个微服务注册到eureka中

spring-cloud-provider-01

package com.example.demo.controller;
import java.util.HashMap;
import java.util.Map;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import com.example.demo.model.User;

@RestController
@RequestMapping(value="/user")
public class UserController {
    private Map<String, User> umap = new HashMap();
    public UserController(){
        umap.put("1", new User("1", "xiaoming1", 30));
        umap.put("2", new User("2", "xiaohong1", 20));
        umap.put("3", new User("3", "zhangsan1", 80));
        umap.put("4", new User("4", "lisi1", 10));
        umap.put("5", new User("5", "wangwu1", 22));
    }
    @RequestMapping(value="/get")
    @ResponseBody
    public User get(String id){
        return umap.get(id);
    }
}

spring-cloud-provider-02

package com.example.demo.controller;
import java.util.HashMap;
import java.util.Map;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

import com.example.demo.model.User;

@RestController
@RequestMapping(value="/user")
public class UserController {
    private Map<String, User> umap = new HashMap();
    public UserController(){
        umap.put("1", new User("1", "xiaoming", 30));
        umap.put("2", new User("2", "xiaohong", 20));
        umap.put("3", new User("3", "zhangsan", 80));
        umap.put("4", new User("4", "lisi", 10));
        umap.put("5", new User("5", "wangwu", 22));
    }
    @RequestMapping(value="/get")
    @ResponseBody
    public User get(String id){
        return umap.get(id);
    }
}

验证

在浏览器中打开:http://192.168.88.101:9000/user/feign_get?id=1

反复刷新浏览器会交替显示下面的json数据

{"id":"1","userName":"xiaoming1","age":30,"birthday":null}
{"id":"1","userName":"xiaoming","age":30,"birthday":null}

问题

在调试feign程序的过程中，经常会出现timeout的问题，可以使用下面的3中方法之一来解决:

hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds: 5000
hystrix.command.default.execution.timeout.enabled: false
feign.hystrix.enabled: false ## 索性禁用feign的hystrix支持