错误信息：java.lang.AbstractMethodError

大家好，又见面了，我是你们的朋友全栈君。

java.lang.AbstractMethodError: org.springframework.cloud.netflix.ribbon.RibbonLoadBalancerClient.choose(Ljava/lang/String;Lorg/springframework/cloud/client/loadbalancer/Request;)Lorg/springframework/cloud/client/ServiceInstance;

错误信息详细如下：

org.springframework.web.util.NestedServletException: Handler dispatch failed; nested exception is 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.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1075)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:962)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:652)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:93)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:888)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1597)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.base/java.lang.Thread.run(Thread.java:844)
Caused by: 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)
	at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:119)
	at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:89)
	at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:100)
	at com.sun.proxy.$Proxy137.getCourseInfoById(Unknown Source)
	at cn.wufen.orderservice.service.impl.TOrderServiceImpl.saveOrder(TOrderServiceImpl.java:39)
	at cn.wufen.orderservice.service.impl.TOrderServiceImpl$$FastClassBySpringCGLIB$$d80bffad.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:688)
	at cn.wufen.orderservice.service.impl.TOrderServiceImpl$$EnhancerBySpringCGLIB$$b434cefb.saveOrder(<generated>)
	at cn.wufen.orderservice.controller.TOrderController.save(TOrderController.java:33)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:564)
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:197)
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:141)
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1060)
	... 43 more

最近在写项目，一部分功能需要通过微服务进行远程调用，需要注册进nacos，加入相关依赖后，系统启动出错（当时没保存错误信息），然后在网上找答案，需要加入依赖，使用loadbalancer负载均衡：

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-loadbalancer</artifactId>
    <version>2.2.5.RELEASE</version>
</dependency>

• 一段时间运行没问题，远程调用微服务，删除阿里云上的视频也没问题。
• 后续需要通过多个微服务远程调用，出现了问题，一直报错！
• 在做评论功能时，就一直报错，功能点做完，一直也没办法测试，也搁置在那!
• 经过分析，发现了原因是因为我引入了loadbalancer负载均衡，当时不知道没有生效，后续发现需要将ribbon排除掉，才能使loadbalancer生效。

<dependency>
     <groupId>org.springframework.cloud</groupId>
     <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
     <!--问题：具体见error文件-->
     <exclusions>
         <exclusion>
             <groupId>org.springframework.cloud</groupId>
             <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
         </exclusion>
     </exclusions>
</dependency>

排除掉ribbon后，远程调用就可以使用了!!!