集成 openfeign 做远程调用和负载均衡
如果没有学 feign 的同学，可以使用 restTemplate 来做出处有坑
步骤回显
- 引入openfeign的依赖
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>
- 被调用的微服务提供接口
@RestController
@RequestMapping("/test")
public class CouponController {
@RequestMapping("/list")
public Result list(@RequestParam Map<String, Object> params){
PageUtils page = couponService.queryPage(params);
return Result.ok().put("page", page);
}
}
- 调用方编写feign的接口
@FeignClient("test1-demo")
public interface TestFeign {
@RequestMapping("/test/list")
Result list();
}
项目用的alibaba的nacos作为注册中心，故@FeignClient(“test1-demo”)的名称为被调用服务接口放的在nacos上的注册名称。
- 开启openFeign
只需要在启动类上如下注解就好了
@SpringBootApplication
@EnableDiscoveryClient
//加入如下注解，开启openFeign
@EnableFeignClients
public class Test2DemoApplication {
public static void main(String[] args) {
SpringApplication.run(Test2DemoApplication.class, args);
}
}
发现报错
缺少依赖,启动报错
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.bearjun.gulimail.member.feign.CouponFeign': Unexpected exception during bean creation; nested exception is java.lang.IllegalStateException: No Feign Client for loadBalancing defined. Did you forget to include spring-cloud-starter-loadbalancer?
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:537) ~[spring-beans-5.3.6.jar:5.3.6]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:335) ~[spring-beans-5.3.6.jar:5.3.6]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-5.3.6.jar:5.3.6]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:333) ~[spring-beans-5.3.6.jar:5.3.6]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:208) ~[spring-beans-5.3.6.jar:5.3.6]
at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276) ~[spring-beans-5.3.6.jar:5.3.6]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1380) ~[spring-beans-5.3.6.jar:5.3.6]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1300) ~[spring-beans-5.3.6.jar:5.3.6]
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:657) ~[spring-beans-5.3.6.jar:5.3.6]
... 21 common frames omitted
Caused by: java.lang.IllegalStateException: No Feign Client for loadBalancing defined. Did you forget to include spring-cloud-starter-loadbalancer?
at org.springframework.cloud.openfeign.FeignClientFactoryBean.loadBalance(FeignClientFactoryBean.java:333) ~[spring-cloud-openfeign-core-3.0.2.jar:3.0.2]
问题分析
由于SpringCloud Feign在Hoxton.M2 RELEASED版本之后不再使用Ribbon而是使用spring-cloud-loadbalancer，所以不引入spring-cloud-loadbalancer会报错。
链接：https://blog.csdn.net/weixin_43556636/article/details/110653989
解决方法
加入spring-cloud-loadbalancer依赖 并且在nacos中排除ribbon依赖，不然loadbalancer无效
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-loadbalancer</artifactId>
</dependency>
依赖冲突
java.lang.AbstractMethodError: org.springframework.cloud.netflix.ribbon.RibbonLoadBalancerClient.choose(Ljava/lang/String;Lorg/springframework/cloud/client/loadbalancer/Request;)Lorg/springframework/cloud/client/ServiceInstance;
at org.springframework.cloud.openfeign.loadbalancer.FeignBlockingLoadBalancerClient.execute(FeignBlockingLoadBalancerClient.java:88) ~[spring-cloud-openfeign-core-3.0.2.jar:3.0.2]
at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:119) ~[feign-core-10.10.1.jar:na]
at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:89) ~[feign-core-10.10.1.jar:na]
at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:100) ~[feign-core-10.10.1.jar:na]
at com.sun.proxy.$Proxy91.list(Unknown Source) ~[na:na]
at com.bearjun.gulimail.member.controller.MemberController.list(MemberController.java:44) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_261]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_261]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_261]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_261]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197) ~[spring-web-5.3.6.jar:5.3.6]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141) ~[spring-web-5.3.6.jar:5.3.6]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.3.6.jar:5.3.6]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894) ~[spring-webmvc-5.3.6.jar:5.3.6]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.6.jar:5.3.6]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.6.jar:5.3.6]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060) ~[spring-webmvc-5.3.6.jar:5.3.6]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962) ~[spring-webmvc-5.3.6.jar:5.3.6]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.6.jar:5.3.6]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.3.6.jar:5.3.6]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:626) ~[tomcat-embed-core-9.0.45.jar:4.0.FR]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.6.jar:5.3.6]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.45.jar:4.0.FR]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:227) ~[tomcat-embed-core-9.0.45.jar:9.0.45]...........
问题分析
nacos中 pring-cloud-starter-netflix-ribbon会与它冲突，造成loadbalanc包失效
解决方法
我们只需要再nacos的服务注册与发现的依赖中去掉ribbon
<dependency>
<groupId>com.alibaba.cloud</groupId>
<artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
<!-- 排除ribbon的依赖 -->
<exclusions>
<exclusion>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
</exclusion>
</exclusions>
</dependency>
Maven显示中央仓库找不到spring-cloud-starter-alibaba-nacos-discovery，去阿里云镜像发现上面版本信息写的unknown，有点懵逼于是去MavenRepository找一下版本号，看一下与SpringCloud适配的版本，Nacos1.3，完事
版本不匹配解决方法如下：
com.alibaba.nacos.api.exception.NacosException: failed to req API解决方案