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SpringCloud学习之feign

一、关于feigin

　　feigin是一种模板化，声明式的http客户端，feign可以通过注解绑定到接口上来简化Http请求访问。当然我们也可以在创建Feign对象时定制自定义解码器(xml或者json等格式解析)和错误处理。

二、添加SpringCloud对feign的支持

gradle配置:

compile('org.springframework.cloud:spring-cloud-starter-feign')

feigin最基本使用方法：

 interface GitHub {

   @RequestLine("GET /repos/{owner}/{repo}/contributors")

   List<Contributor> contributors(@Param("owner") String owner, @Param("repo") String repo);

 }

 static class Contributor {

   String login;

   int contributions;

 }

 public static void main(String... args) {

   GitHub github = Feign.builder()

                        .decoder(new GsonDecoder())

                        .target(GitHub.class, "https://api.github.com");

   // Fetch and print a list of the contributors to this library.

   List<Contributor> contributors = github.contributors("OpenFeign", "feign");

   for (Contributor contributor : contributors) {

     System.out.println(contributor.login + " (" + contributor.contributions + ")");

   }

 }

feign发送json与xml的格式的http请求：

 interface LoginClient {

   @RequestLine("POST /")

   @Headers("Content-Type: application/xml")

   @Body("<login \"user_name\"=\"{user_name}\" \"password\"=\"{password}\"/>")

   void xml(@Param("user_name") String user, @Param("password") String password);

   @RequestLine("POST /")

   @Headers("Content-Type: application/json")

   // json curly braces must be escaped!

   @Body("%7B\"user_name\": \"{user_name}\", \"password\": \"{password}\"%7D")

   void json(@Param("user_name") String user, @Param("password") String password);

 }

注意示例中需要添加对gson的支持

feign发送https信任所有证书的代码:

 final TrustManager[] trustAllCerts = new TrustManager[]{new X509TrustManager() {

             @Override

             public void checkClientTrusted(

                     java.security.cert.X509Certificate[] chain,

                     String authType) {

             }

             @Override

             public void checkServerTrusted(

                     java.security.cert.X509Certificate[] chain,

                     String authType) {

             }

             @Override

             public java.security.cert.X509Certificate[] getAcceptedIssuers() {

                 return null;

             }

         }};

         final SSLContext sslContext = SSLContext.getInstance("TLSv1");

         sslContext.init(null, trustAllCerts,

                 new java.security.SecureRandom());

         // Create an ssl socket factory with our all-trusting manager

         final SSLSocketFactory sslSocketFactory = sslContext

                 .getSocketFactory();

         Feign.builder().client(new Client.Default(sslSocketFactory, (s, sslSession) -> true));

三、在SpringCloud中使用Feign

比如说注册中心有如下服务：

SpringCloud学习之feign-LMLPHP

1）application.yml的配置：

spring:

  application:

    name: demo-consumer

eureka:

  client:

    service-url:

      defaultZone: http://localhost:8080/eureka,http://localhost:8081/eureka

server:

  port: 8090

2）创建接口

 package com.bdqn.lyrk.consumer.demo.api;

 import org.springframework.cloud.netflix.feign.FeignClient;

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

 @FeignClient("demo")

 public interface DemoConfigService {

     @RequestMapping("/demo.do")

     String demoService();

 }

注意在接口上加上注解：@FeignClient("demo") 注解里的参数是在eureka注册的服务名

3）编写启动类：

package com.bdqn.lyrk.consumer.demo;

import com.bdqn.lyrk.consumer.demo.api.DemoConfigService;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

import org.springframework.cloud.netflix.feign.EnableFeignClients;

import org.springframework.context.ConfigurableApplicationContext;

@EnableDiscoveryClient

@EnableFeignClients

@SpringBootApplication

public class DemoConsumerProvider {

    public static void main(String[] args) {

        ConfigurableApplicationContext applicationContext = SpringApplication.run(DemoConsumerProvider.class, args);

        DemoConfigService demoConfigService = applicationContext.getBean(DemoConfigService.class);

        System.out.println(demoConfigService.demoService());

    }

}

注意在启动类上加上@EnableFeignClients来开启Feign功能

运行后输出：

SpringCloud学习之feign-LMLPHP

此时我们可以发现使用feign客户端我们访问服务的代码简洁了好多

4) feign多参数设置方法

service-api模块的接口定义：

public interface IBillService {

    @PostMapping("/queryBill")

    List<BillDTO> queryOrders(@RequestBody  BillsVO billsVO);

}

相关服务实现类：

@RestController

public class BillServiceImpl implements IBillService {

    @Autowired

    private BillMapper billMapper;

    @PostMapping("/queryBill")

    @Override

    public List<BillDTO> queryOrders(@RequestBody BillsVO billsVO) {

        return billMapper.query(BeanMap.create(billsVO));

    }

}

注意 需要在接口定义与实现类的参数上加@RequestBody注解

四、feign中的使用Hystrix

　　1) 在@FeignClient中有两个属性我们值得关注一下，它们分别是fallBack和fallBackFactory，当然我们系统里要添加Hystrix支持并且在属性文件里设置：

feign.hystrix.enabled=true

　　同样我们要在启动类里加上@EnableCircuitBreaker注解打开Hystrix保护

　　

　　2) fallBack属性很简单，用来设置降级方法，当feign请求服务失败时所调用的方法, 这里我给出接口的例子：

　　首先定义一个接口：IOrderService　　

package com.bdqn.lyrk.service.api;

import com.bdqn.lyrk.service.dto.OrderDTO;

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

import org.springframework.web.bind.annotation.PathVariable;

public interface IOrderService {

    @GetMapping("/orderId/{orderId}")

    OrderDTO getOrderById(@PathVariable("orderId") Integer orderId);

    @GetMapping("/errorOrder")

    OrderDTO getErrorOrder();

}

　　其次定义Feign的接口OrderServiceClient继承IOrderService

package com.bdqn.lyrk.order.service.consumer.feign;

import com.bdqn.lyrk.service.api.IOrderService;

import org.springframework.cloud.openfeign.FeignClient;

import org.springframework.context.annotation.Primary;

@Primary

@FeignClient(value = "ORDER-SERVER", fallBack="FailedOrderServiceClientImpl.class")

public interface OrderServiceClient extends IOrderService {

}

　　由于IOrderService不在同一个项目里，而且SpringCloud不推荐服务端和客户端使用同一个接口，所以我采用继承的方式，注意加上@Primary注解以免使用@Autowired时注入失败

　　在定义实现类：

package com.bdqn.lyrk.order.service.consumer.feign;

import com.bdqn.lyrk.service.dto.OrderDTO;

import org.springframework.stereotype.Component;

@Component

public class FailedOrderServiceClientImpl implements OrderServiceClient {

    @Override

    public OrderDTO getOrderById(Integer orderId) {

        OrderDTO orderDTO = new OrderDTO();

        orderDTO.setId(orderId);

        orderDTO.setOrderName("服务中失败的订单,id为：" + orderId);

        return null;

    }

    @Override

    public OrderDTO getErrorOrder() {

        OrderDTO orderDTO = new OrderDTO();

        orderDTO.setOrderName("服务中失败的订单");

        orderDTO.setId(-1);

        return orderDTO;

    }

}

　　最后@FeignClient中设置属性fallBack="FailedOrderServiceClientImpl.class" 就可以了

　　3) 当我们需要封装服务端的异常信息时，可以指定fallbackFactory属性，请看下面的例子：

　　

package com.bdqn.lyrk.order.service.consumer.feign;

import com.bdqn.lyrk.service.dto.OrderDTO;

import feign.hystrix.FallbackFactory;

import org.springframework.stereotype.Component;

@Component

public class OrderServiceFallbackFactoryImpl implements FallbackFactory<OrderServiceClient> {

    @Override

    public OrderServiceClient create(Throwable cause) {

       return new OrderServiceClient() {

           @Override

           public OrderDTO getOrderById(Integer orderId) {

               OrderDTO orderDTO = new OrderDTO();

               orderDTO.setOrderName(cause.getMessage());

               return orderDTO;

           }

           @Override

           public OrderDTO getErrorOrder() {

               OrderDTO orderDTO = new OrderDTO();

               orderDTO.setOrderName(cause.getMessage());

               return orderDTO;

           }

       };

    }

}

　　注意：FallbackFactory的泛型参数一定要指定为@FeignClient修饰的接口，同时不建议fallback与fallbackFactory同时使用

　　最后 我贴一下服务端的实现代码：

　　

package com.bdqn.lyrk.springcloud.order.service;

import com.bdqn.lyrk.service.api.IOrderService;

import com.bdqn.lyrk.service.dto.OrderDTO;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty;

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

import org.springframework.web.bind.annotation.PathVariable;

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

import java.util.concurrent.TimeUnit;

@RestController

public class OrderServiceImpl implements IOrderService {

    @HystrixCommand(fallbackMethod = "errorDTO",

            commandProperties = {@HystrixProperty(name = "execution.isolation.thread.timeoutInMilliseconds", value = "3000")}

    )

    @GetMapping("/orderId/{orderId}")

    @Override

    public OrderDTO getOrderById(@PathVariable("orderId") Integer orderId) {

        OrderDTO orderDTO = new OrderDTO();

        orderDTO.setId(orderId);

        orderDTO.setOrderName("订单ID为" + orderId + "的订单");

        try {

            TimeUnit.SECONDS.sleep(orderId);

        } catch (InterruptedException e) {

            throw new RuntimeException(e);

        }

        return orderDTO;

    }

    @Override

    public OrderDTO getErrorOrder() {

        System.out.println(1 / 0);

        return null;

    }

    public OrderDTO errorDTO(Integer orderId) {

        OrderDTO orderDTO = new OrderDTO();

        orderDTO.setId(-1);

        orderDTO.setOrderName("错误的订单，请重试");

        return orderDTO;

    }

}

　　对于Hystrix可以参考：SpringCloud学习之Hystrix

05-02 09:13
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