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从零开始认识Dubbo-创新互联

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1.Dubbo是什么

http://dubbo.apache.org/zh-cn/index.html

Apache Dubbo™ 是一款高性能Java RPC框架。

Dubbo是一个分布式服务框架，致力于提供高性能和透明化的RPC远程服务调用方案，以及SOA服务治理方案。简单的说，dubbo就是个服务框架，如果没有分布式的需求，其实是不需要用的，只有在分布式的时候，才有dubbo这样的分布式服务框架的需求，并且本质上是个服务调用的东东，说白了就是个远程服务调用的分布式框架（告别Web Service模式中的WSdl，以服务者与消费者的方式在dubbo上注册）
其核心部分包含:

  1. 远程通讯: 提供对多种基于长连接的NIO框架抽象封装，包括多种线程模型，序列化，以及“请求-响应”模式的信息交换方式。

  2. 集群容错: 提供基于接口方法的透明远程过程调用，包括多协议支持，以及软负载均衡，失败容错，地址路由，动态配置等集群支持。

  3. 自动发现: 基于注册中心目录服务，使服务消费方能动态的查×××提供方，使地址透明，使服务提供方可以平滑增加或减少机器。

2.Dubbo能做什么

  1. 透明化的远程方法调用，就像调用本地方法一样调用远程方法，只需简单配置，没有任何API侵入。
  2. 软负载均衡及容错机制，可在内网替代F5等硬件负载均衡器，降低成本，减少单点。
  3. 服务自动注册与发现，不再需要写死服务提供方地址，注册中心基于接口名查询服务提供者的IP地址，并且能够平滑添加或删除服务提供者。

Dubbo采用全spring配置方式，透明化接入应用，对应用没有任何API侵入，只需用Spring加载Dubbo的配置即可，Dubbo基于Spring的Schema扩展进行加载。

3.Dubbo架构

从零开始认识Dubbo

节点角色说明：

​ Provider: 暴露服务的服务提供方。

​ Consumer: 调用远程服务的服务消费方。

​ Registry: 服务注册与发现的注册中心。

​ Monitor: 统计服务的调用次调和调用时间的监控中心。

​ Container: 服务运行容器。

调用关系说明：

  1. 服务容器负责启动，加载，运行服务提供者。

  2. 服务提供者在启动时，向注册中心注册自己提供的服务。

  3. 服务消费者在启动时，向注册中心订阅自己所需的服务。

  4. 注册中心返回服务提供者地址列表给消费者，如果有变更，注册中心将基于长连接推送变更数据给消费者。

  5. 服务消费者，从提供者地址列表中，基于软负载均衡算法，选一台提供者进行调用，如果调用失败，再选另一台调用。

  6. 服务消费者和提供者，在内存中累计调用次数和调用时间，定时每分钟发送一次统计数据到监控中心。

4.Dubbo的使用方法

Dubbo采用全Spring配置方式，透明化接入应用，对应用没有任何API侵入，只需用Spring加载Dubbo的配置即可，Dubbo基于Spring的Schema扩展进行加载。如果不想使用Spring配置，可以通过API的方式进行调用（注解式，不推荐使用）

下载安装zookeeper注册中心（不建议使用multicast）
1.Windows

下载地址：https://www.apache.org/dyn/closer.cgi/zookeeper/

使用方法：下载解压即可，进入解压目录运行zkServer.cmd启动注册服务中心

截图：

从零开始认识Dubbo

2.MacOS

下载地址：https://www.apache.org/dyn/closer.cgi/zookeeper/

使用方法：下载解压即可，进入解压目录运行zkServer.sh start启动注册服务中心

3.Linux

下载地址：https://www.apache.org/dyn/closer.cgi/zookeeper/

使用方法：下载解压即可，进入解压目录运行zkServer.sh start启动注册服务中心

服务提供者
1.定义服务接口(该接口需单独打包，在服务提供方和消费方共享)

DemoService.java

package org.apache.dubbo.demo;

public interface DemoService {
    String sayHello(String name);
}
2.服务提供方实现接口：(对服务消费方隐藏实现)

DemoServiceImpl.java

package org.apache.dubbo.demo.provider;

import org.apache.dubbo.demo.DemoService;

public class DemoServiceImpl implements DemoService {
    public String sayHello(String name) {
        return "Hello " + name;
    }
}
3.用Spring配置声明暴露服务：

dubbo-provider.xml：

?xml version="1.0" encoding="UTF-8"?>
4.加载Spring配置，启动服务：

Provider.java：

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Provider {
    public static void main(String[] args) throws Exception {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[] {"spring/dubbo-provider.xml"});
        context.start();
        System.in.read(); // 按任意键退出
    }
}

或者使用springBoot启动

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ImportResource;

@SpringBootApplication
@ImportResource("spring/dubbo-provider.xml")
public class DubboProviderApplication {

    public static void main(String[] args) throws Exception {
        SpringApplication.run(DubboProviderApplication.class, args);

    }
}
服务消费者：

applicationContext-dubbo.xml 中注册自己需要调用的接口。

1.通过Spring配置引用远程服务

dubbo-consumer.xml：
2.加载Spring配置，并调用远程服务：

Consumer.java

import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.apache.dubbo.demo.DemoService;

public class Consumer {
    public static void main(String[] args) throws Exception {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[] {"spring/dubbo-consumer.xml"});
        context.start();
        DemoService demoService = (DemoService)context.getBean("demoService"); // 获取远程服务代理
        String hello = demoService.sayHello("world"); // 执行远程方法
        System.out.println( hello ); // 显示调用结果
    }
}

或者使用springBoot启动

import org.apache.dubbo.common.logger.Logger;
import org.apache.dubbo.common.logger.LoggerFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.ImportResource;

@SpringBootApplication
@ImportResource("spring/dubbo-consumer.xml")
public class DubboConsumerApplicaiton {

    public static final Logger logger = LoggerFactory.getLogger(DubboConsumerApplicaiton.class);

    public static void main(String[] args) {
        SpringApplication.run(DubboConsumerApplicaiton.class, args);

    }
}

并添加对应的restful接口提供接口访问

@RequestMapping("/demo")
public ModelAndView testDemo() {
    ModelAndView modelAndView = new ModelAndView("index");
    org.apache.dubbo.rpc.RpcContext.getContext().setAttachment(Constants.TAG_KEY, "gray");
    modelAndView.addObject("result", demoService.sayHello("Dubbo Meetup"));
    return modelAndView;
}

修改对应index页面




    
    Vertical centering in valid CSS
    




${result.msg}


From : ${result.userName}
3.dubbo管理页面：

https://github.com/apache/dubbo-admin

启动后访问 http://localhost:8080/dubbo-admin/

输入账号密码root/root

从零开始认识Dubbo

从零开始认识Dubbo

应用页面：

从零开始认识Dubbo

提供者页面:

从零开始认识Dubbo

消费者页面：

从零开始认识Dubbo

服务页面：

从零开始认识Dubbo

测试是否成功，只要看状态是否正常，就ok了 ....

从零开始认识Dubbo

provider-log:

2019-07-04 11:37:49,326 [DubboServerHandler-192.168.0.46:20880-thread-2] INFO  org.apache.dubbo.demo.impl.DemoServiceImpl (DemoServiceImpl.java:31) -  [DUBBO] [11:37:49] Hello Alterem., request from consumer: /192.168.0.46:52031, dubbo version: 2.7.0, current host: 192.168.0.46

5.使用Dubbo可能遇到的问题

1、org.springframework.beans.factory.BeanCreationException
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'mgmtFactoryInoutDetailsController': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'goodsInoutServiceImpl' available
    at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:321) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1268) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:312) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:308) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.web.method.HandlerMethod.createWithResolvedBean(HandlerMethod.java:299) ~[spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.getHandlerInternal(AbstractHandlerMethodMapping.java:323) ~[spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.getHandlerInternal(AbstractHandlerMethodMapping.java:61) ~[spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.handler.AbstractHandlerMapping.getHandler(AbstractHandlerMapping.java:352) ~[spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.getHandler(DispatcherServlet.java:1160) [spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:940) [spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) [spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.proce***equest(FrameworkServlet.java:970) [spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) [spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) [servlet-api.jar:na]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) [spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) [servlet-api.jar:na]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-websocket.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90) [shiro-core-1.2.4.jar:1.2.4]
    at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83) [shiro-core-1.2.4.jar:1.2.4]
    at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383) [shiro-core-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125) [shiro-web-1.2.4.jar:1.2.4]
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:347) [spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:263) [spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) [spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at ue.common.filter.MultiPrefixHideUrlFilter.doFilter(MultiPrefixHideUrlFilter.java:76) [YKXCommon-3.3.01.jar:na]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at ue.common.filter.PageableFilter.doFilterInternal(PageableFilter.java:48) [YKXCommon-3.3.01.jar:na]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) [catalina.jar:8.0.36]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) [catalina.jar:8.0.36]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) [catalina.jar:8.0.36]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) [catalina.jar:8.0.36]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [catalina.jar:8.0.36]
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) [catalina.jar:8.0.36]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) [catalina.jar:8.0.36]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528) [catalina.jar:8.0.36]
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1099) [tomcat-coyote.jar:8.0.36]
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:670) [tomcat-coyote.jar:8.0.36]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1520) [tomcat-coyote.jar:8.0.36]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1476) [tomcat-coyote.jar:8.0.36]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_131]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_131]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-util.jar:8.0.36]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_131]
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'goodsInoutServiceImpl' available
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinition(DefaultListableBeanFactory.java:687) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getMergedLocalBeanDefinition(AbstractBeanFactory.java:1213) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:284) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:275) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:522) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:496) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:627) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:169) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88) ~[spring-beans-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:318) ~[spring-context-4.3.16.RELEASE.jar:4.3.16.RELEASE]
    ... 67 common frames omitted

原因分析：

Error creating bean with name 'mgmtFactoryInoutDetailsController': Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No bean named 'goodsInoutServiceImpl' available
    at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessPropertyValues(CommonAnnotationBeanPostProcessor.java:321)

解决方案

在dubbo-provider.xml添加对应的声明暴露服务

在dubbo-consumer.xml添加对应的服务订阅

2、org.apache.dubbo.rpc.RpcException
org.apache.dubbo.rpc.RpcException: No provider available from registry 120.79.246.86:2181 for service ue.biz.service.bas.EnterpriseUserService on consumer 192.168.0.63 use dubbo version 2.7.0, please check status of providers(disabled, not registered or in blacklist).
    at org.apache.dubbo.registry.integration.RegistryDirectory.doList(RegistryDirectory.java:522) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.cluster.directory.AbstractDirectory.list(AbstractDirectory.java:82) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.cluster.support.AbstractClusterInvoker.list(AbstractClusterInvoker.java:274) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.cluster.support.AbstractClusterInvoker.invoke(AbstractClusterInvoker.java:238) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.cluster.support.wrapper.MockClusterInvoker.invoke(MockClusterInvoker.java:75) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.proxy.InvokerInvocationHandler.invoke(InvokerInvocationHandler.java:57) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.common.bytecode.proxy7.getCurrent(proxy7.java) ~[dubbo-2.7.0.jar:2.7.0]
    at ue.mgmt.controller.CommonController.main(CommonController.java:787) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_131]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_131]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_131]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_131]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) ~[spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133) ~[spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97) ~[spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:849) ~[spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:760) ~[spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967) [spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901) [spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.proce***equest(FrameworkServlet.java:970) [spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) [spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) [servlet-api.jar:na]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) [spring-webmvc-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) [servlet-api.jar:na]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) [tomcat-websocket.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90) [shiro-core-1.2.4.jar:1.2.4]
    at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83) [shiro-core-1.2.4.jar:1.2.4]
    at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383) [shiro-core-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362) [shiro-web-1.2.4.jar:1.2.4]
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125) [shiro-web-1.2.4.jar:1.2.4]
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:347) [spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:263) [spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) [spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at ue.common.filter.MultiPrefixHideUrlFilter.doFilter(MultiPrefixHideUrlFilter.java:76) [YKXCommon-3.3.01.jar:na]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at ue.common.filter.PageableFilter.doFilterInternal(PageableFilter.java:48) [YKXCommon-3.3.01.jar:na]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) [spring-web-4.3.20.RELEASE.jar:4.3.20.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240) [catalina.jar:8.0.36]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207) [catalina.jar:8.0.36]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212) [catalina.jar:8.0.36]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) [catalina.jar:8.0.36]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) [catalina.jar:8.0.36]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141) [catalina.jar:8.0.36]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [catalina.jar:8.0.36]
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) [catalina.jar:8.0.36]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) [catalina.jar:8.0.36]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:528) [catalina.jar:8.0.36]
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1099) [tomcat-coyote.jar:8.0.36]
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:670) [tomcat-coyote.jar:8.0.36]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1520) [tomcat-coyote.jar:8.0.36]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1476) [tomcat-coyote.jar:8.0.36]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_131]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_131]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-util.jar:8.0.36]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_131]

原因分析

No provider available from registry 120.79.246.86:2181 for service ue.biz.service.bas.EnterpriseUserService on consumer 192.168.0.63 use dubbo version 2.7.0, please check status of providers

解决方案

可能是因为providers没有启动，或者是provider对应暴露的服务被禁用，启动providers或者解除禁用即可

3、java.lang.IllegalStateException
java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load [io.netty.channel.nio.NioEventLoop]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
    at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading(WebappClassLoaderBase.java:1352)
    at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1340)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1205)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1166)
    at ch.qos.logback.classic.spi.PackagingDataCalculator.loadClass(PackagingDataCalculator.java:207)
    at ch.qos.logback.classic.spi.PackagingDataCalculator.bestEffortLoadClass(PackagingDataCalculator.java:226)
    at ch.qos.logback.classic.spi.PackagingDataCalculator.computeBySTEP(PackagingDataCalculator.java:138)
    at ch.qos.logback.classic.spi.PackagingDataCalculator.populateUncommonFrames(PackagingDataCalculator.java:113)
    at ch.qos.logback.classic.spi.PackagingDataCalculator.populateFrames(PackagingDataCalculator.java:105)
    at ch.qos.logback.classic.spi.PackagingDataCalculator.calculate(PackagingDataCalculator.java:57)
    at ch.qos.logback.classic.spi.ThrowableProxy.calculatePackagingData(ThrowableProxy.java:147)
    at ch.qos.logback.classic.spi.LoggingEvent.(LoggingEvent.java:124)
    at ch.qos.logback.classic.Logger.buildLoggingEventAndAppend(Logger.java:440)
    at ch.qos.logback.classic.Logger.filterAndLog_0_Or3Plus(Logger.java:396)
    at ch.qos.logback.classic.Logger.warn(Logger.java:713)
    at io.netty.util.internal.logging.Slf4JLogger.warn(Slf4JLogger.java:151)
    at io.netty.channel.nio.NioEventLoop.handleLoopException(NioEventLoop.java:486)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:469)
    at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884)
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
    at java.lang.Thread.run(Thread.java:748)

原因分析

this web application instance has been stopped already.
所以，需要重启Tomcat的情况下才有可能发上，这是第一个出错条件。
Could not load [io.netty.channel.nio.NioEventLoop].
看这个不能直接推出问题产生条件，但是很明显是关于加载的。

解决方案

总结以上两点，通俗点讲，就是重启了工程（可能是因为直接修改代码，工程reload了）， 并且，连过了数据库（登录等），才出现了上述报错信息。
原因是因为在tomcat重启的时候，之前的tomcat的线程还没有完全关闭，最新启动tomcat就会报这个异常。

4、org.apache.dubbo.remoting.TimeoutException
Caused by: org.apache.dubbo.remoting.TimeoutException: Waiting server-side response timeout by scan timer. start time: 2019-07-04 15:05:41.363, end time: 2019-07-04 15:05:51.388, client elapsed: 94 ms, server elapsed: 9931 ms, timeout: 10000 ms, request: Request [id=0, version=2.0.2, twoway=true, event=false, broken=false, data=RpcInvocation [methodName=find, parameterTypes=[class ue.biz.entity.sys.Permission$Type], arguments=[url], attachments={path=ue.biz.service.sys.PermissionService, interface=ue.biz.service.sys.PermissionService, version=0.0.0, timeout=10000}]], channel: /192.168.0.46:54424 -> /192.168.0.46:20880
    at org.apache.dubbo.remoting.exchange.support.DefaultFuture.returnFromResponse(DefaultFuture.java:296) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.remoting.exchange.support.DefaultFuture.get(DefaultFuture.java:191) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.remoting.exchange.support.DefaultFuture.get(DefaultFuture.java:164) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.protocol.dubbo.DubboInvoker.doInvoke(DubboInvoker.java:108) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.protocol.AbstractInvoker.invoke(AbstractInvoker.java:156) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.monitor.support.MonitorFilter.invoke(MonitorFilter.java:88) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:73) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.protocol.dubbo.filter.FutureFilter.invoke(FutureFilter.java:49) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:73) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.filter.ConsumerContextFilter.invoke(ConsumerContextFilter.java:54) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper$1.invoke(ProtocolFilterWrapper.java:73) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.listener.ListenerInvokerWrapper.invoke(ListenerInvokerWrapper.java:77) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.protocol.InvokerWrapper.invoke(InvokerWrapper.java:56) ~[dubbo-2.7.0.jar:2.7.0]
    at org.apache.dubbo.rpc.cluster.support.FailoverClusterInvoker.doInvoke(FailoverClusterInvoker.java:80) ~[dubbo-2.7.0.jar:2.7.0]
    ... 65 common frames omitted

原因分析

org.apache.dubbo.remoting.TimeoutException: Waiting server-side response timeout by scan timer. start time: 2019-07-04 15:05:41.363, end time: 2019-07-04 15:05:51.388, client elapsed: 94 ms, server elapsed: 9931 ms, timeout: 10000 ms, request: Request [id=0, version=2.0.2, twoway=true, event=false, broken=false, data=RpcInvocation [methodName=find, parameterTypes=[class ue.biz.entity.sys.Permission$Type], arguments=[url], attachments={path=ue.biz.service.sys.PermissionService

解决方案

在dubbo-provider.xml增加超时时间

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文章题目：从零开始认识Dubbo-创新互联
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