SpringCloud Feign声明式服务调用
1. 加入pom依赖
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
2. Application.java上声明@EnableFeignClients
表示允许声明式feign调用
@EnableEurekaClient
@SpringBootApplication
@EnableFeignClients(basePackages = {
"com.service.client.feign.inter" })
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
3. @FeignClient声明接口调用服务名,(SpirngMVC绑定方法,可有可无)
接口@FeignClient注解指定服务名来绑定服务,然后再使用Spring MVC的注解来绑定具体该服务提供的REST接口。
@FeignClient("hello-service-provider")
public interface HelloServiceFeign {
@RequestMapping(value = "/demo/getHost", method = RequestMethod.GET)
public String getHost(String name);
@RequestMapping(value = "/demo/postPerson", method = RequestMethod.POST, produces = "application/json; charset=UTF-8")
public Person postPerson(String name);
注意,(SpirngMVC绑定方法,可有可无),若写则@RequestMapping需要写全面,假如XXInterface中Controller层也有 @RestController, @RequestMapping("/hello")
则应该为:
@FeignClient("hello-service-provider")
public interface HelloServiceFeign {
@RequestMapping(value = "/hello/demo/getHost", method = RequestMethod.GET)
public String getHost(String name);
@RequestMapping(value = "/hello/demo/postPerson", method = RequestMethod.POST, produces = "application/json; charset=UTF-8")
public Person postPerson(String name);
}
4. Feign负载均衡是通过ribbon实现的
Spring Cloud Feign的客户端负载均衡是通过Spring Cloud Ribbon实现的,可以直接配置Ribbon客户端的方式来自定义各个服务客户端调用参数。
Spring Cloud Ribbon默认负载均衡策略是轮询策略,不过该不一定满足我们的需要。Ribbon一共提供了7种负载均衡策略,如果我们需要ZoneAvoidanceRule,首先要在application.properties文件中添加配置,如下所示:
ribbon.NFLoadBalancerRuleClassName=com.netflix.loadbalancer.ZoneAvoidanceRule
不过,只是添加了如上配置,还无法实现负载均衡策略的更改。还需要实例化该策略,可以在应用主类中直接加入IRule实例的创建,如下:
/**
* 服务调用者,,eureka客户端 feign调用
*
* @version
* @since 1.8
*/
@EnableEurekaClient
@SpringBootApplication
@EnableFeignClients(basePackages = {
"com.client.feign.inter" })
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
@Bean
public IRule feignRule() {
return new ZoneAvoidanceRule();
}
}
5. 常见问题与解决
- 遇到404,检查@GetMapping中url
- 超时,application.yml配置ribbon
- 还报超时,访问不到,有可能跨域问题
在controller层增加 @CrossOrigin;
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- 没报错,就是返回结果不是期望的值,有可能程序中间有异常报错
日志如上,被调用的服务日志打印完全一致,结果不是想要的,最后发现是程序后续处理过程有bug…;
6. 小技巧,可调试用
在url处配置服务的ip与端口,调试程序问题;
@FeignClient(name="hello-service-provider",url="http://xxx.xxx.xxx.xxx/")
public interface HelloServiceFeign {
@RequestMapping(value = "/hello/demo/getHost", method = RequestMethod.GET)
public String getHost(String name);
@RequestMapping(value = "/hello/demo/postPerson", method = RequestMethod.POST, produces = "application/json; charset=UTF-8")
public Person postPerson(String name);
}