各个章节可能有关联关系，查找《SpringCloud实战教程》其他章节请参考：
http://www.yayihouse.com/yayishuwu/book/79
7. Springcloud在Feign中整合断路器Hystrix实现发生异常时友好提示
feign客户端代码：
(1) Pom.xml依赖，feign整合了Hystrix，不用另外添加依赖：
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.wlg.springcloud</groupId>
<artifactId>springcloud</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<groupId>com.wlg.springcloud</groupId>
<artifactId>euraka-client-feifn</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>euraka-client-feifn</name>
<description>Demo project for Spring Boot</description>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
</dependencies>
</project>
(2) application.yml:
server:
port: 9903
spring:
application:
name: service-two
eureka:
client:
serviceUrl:
defaultZone: http://localhost:9901/eureka/
(3) Feign接口加上fallback = FeignClientServiceImp.class：
当用户访问sayHello传参数txt为0时抛出异常，那么就会执行fallback返回信息给用户
@FeignClient(value = "service-one",fallback = FeignClientServiceImp.class)
public interface FeignClientService {
@RequestMapping("/hello")
public String sayHello(@RequestParam("txt")String txt);
}
(4) FeignClientServiceImp内容如下，方法要和接口的方法一致：
public class FeignClientServiceImp {
public String sayHello(String txt) {
return "系统维护中，请稍后再试。。。";
}
}
(1) 通过feign接口调用其他服务
@Controller
public class FeignClientController {
@Autowired
private FeignClientService feignClientService;
@RequestMapping("/sayHello")
public void sayHello(String txt, HttpServletResponse response) throws IOException {
String result = feignClientService.sayHello(txt);
response.setCharacterEncoding("utf-8");
response.setContentType("text/html; charset=utf-8");
PrintWriter writer = response.getWriter();
writer.print(result);
writer.flush();
writer.close();
}
}
(2) 被调用的工程eureka-client被调用的方法（在注册中心的服务名为service-one，前面章节创建了）
@RequestMapping("/hello")
@ResponseBody
public String sayHello(@RequestParam("txt") String txt) throws Exception {
if("0".equals(txt)){
throw new Exception();
}
return "收到你传过来的参数为："+txt;
}
(3) 演示：
启动前面章节创建的服务发现及注册中心eurekaServer，启动被调用的服务eureka-client，启动feign客户端（端口9903）
浏览器访问：http://localhost:9903/sayHello?txt=1
没异常事的结果：收到你传过来的参数为：1
浏览器访问：http://localhost:9903/sayHello?txt=0
有异常结果：收到你传过来的参数为：0,但系统正在维护中。。。
这就说明了hystrix捕捉并处理了异常