在springboot中使用dubbo，本来是件挺简单的事情，但现实的世界就是如此的复杂，今天我用一个亲身经历的跳坑和填坑的事来讲在spring boot中使用高版本dubbo（当当的魔改版）的三重境界。
1、看山是山，使用官方starter
简单的使用dubbo starter集成进spring boot还是非常简单的。
在springboot2的pom.xml中引入dubbo的starter
<dependency>
<groupId>com.alibaba.spring.boot</groupId>
<artifactId>dubbo-spring-boot-starter</artifactId>
<version>2.0.0</version>
</dependency>在启动类里面加上注解@EnableDubboConfiguration
@EnableDubboConfiguration
@SpringBootApplication
public class DubbodemoApplication {
public static void main(String[] args) {
SpringApplication.run(DubbodemoApplication.class, args);
}
}在application.properties里面写dubbo的相关配置
spring.dubbo.application.name=mydubbostarterdemo
spring.dubbo.server=true
spring.dubbo.protocol.name=dubbo
spring.dubbo.registry.address=zookeeper://127.0.0.1:2181作为服务的提供者，我们发布一个服务
public interface IHelloService {
public String hello(String str);
}import com.alibaba.dubbo.config.annotation.Service;
//这个service的注解是dubbo的service，不是spring的service注解
@Service(interfaceClass = IHelloService.class)
@Component
public class HelloServiceImpl implements IHelloService {
@Override
public String hello(String str) {
String returnStr = "Hello "+str;
return returnStr;
}
}然后运行DubbodemoApplication就能发布这个服务了。
同样的，在消费者那边，我们直接用@Reference注解来引用这个服务即可
@Reference
private IHelloService helloService;
@GetMapping("/hello/{name}")
public String hello(@PathVariable("name") String name) {
String str = helloService.hello(name);
System.out.println(str);
return str;
}记得在消费者的工程里面要加上IHelloService的接口类。
这样就能愉快的调用了
是不是很简单，是不是很容易。但是这个世界是复杂的，我们看下pom文件可以看到，里面引用的dubbo版本是2.6.0
但现在很多地方用的并不是dubbo，而是当当改过的dubbo，最新的版本已经到了2.8.4，如果服务提供者用这个版本，那么消费者还用这种方法调用，就会报错
2019-12-05 11:51:28.094 ERROR 17808 --- [nio-8088-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is com.alibaba.dubbo.rpc.RpcException: Failed to invoke the method hello in the service com.skyblue.dubbodemo.service.IHelloService. Tried 3 times of the providers [192.168.1.103:20880] (1/1) from the registry 115.29.199.6:2181 on the consumer 192.168.1.103 using the dubbo version 2.6.0. Last error is: Failed to invoke remote method: hello, provider: dubbo://192.168.1.103:20880/com.skyblue.dubbodemo.service.IHelloService?anyhost=true&application=mydubbostarterdemo&check=false&dubbo=2.8.4a&generic=false&interface=com.skyblue.dubbodemo.service.IHelloService&methods=hello&pid=17808®ister.ip=192.168.1.103&remote.timestamp=1575517827193&side=consumer×tamp=1575517879746, cause: Fail to decode request due to: RpcInvocation [methodName=hello, parameterTypes=null, arguments=null, attachments={path=com.skyblue.dubbodemo.service.IHelloService, input=223, dubbo=2.6.0, version=0.0.0}]] with root cause
com.alibaba.dubbo.remoting.RemotingException: Fail to decode request due to: RpcInvocation [methodName=hello, parameterTypes=null, arguments=null, attachments={path=com.skyblue.dubbodemo.service.IHelloService, input=223, dubbo=2.6.0, version=0.0.0}]
at com.alibaba.dubbo.remoting.exchange.support.DefaultFuture.returnFromResponse(DefaultFuture.java:218) ~[dubbo-2.6.0.jar:2.6.0]
at com.alibaba.dubbo.remoting.exchange.support.DefaultFuture.get(DefaultFuture.java:137) ~[dubbo-2.6.0.jar:2.6.0]
at com.alibaba.dubbo.remoting.exchange.support.DefaultFuture.get(DefaultFuture.java:111) ~[dubbo-2.6.0.jar:2.6.0]
at com.alibaba.dubbo.rpc.protocol.dubbo.DubboInvoker.doInvoke(DubboInvoker.java:95) ~[dubbo-2.6.0.jar:2.6.0]
at com.alibaba.dubbo.rpc.protocol.AbstractInvoker.invoke(AbstractInvoker.java:142) ~[dubbo-2.6.0.jar:2.6.0]
......同样，提供服务端也是报错
2019-12-05 12:00:55.144 WARN 7412 --- [w I/O worker #7] c.a.d.r.p.dubbo.DecodeableRpcInvocation : [DUBBO] Decode rpc invocation failed: expected integer at 0x12 java.lang.String (Ljava/lang/String;), dubbo version: 2.8.4a, current host: 192.168.1.103
com.alibaba.com.caucho.hessian.io.HessianProtocolException: expected integer at 0x12 java.lang.String (Ljava/lang/String;)
at com.alibaba.com.caucho.hessian.io.Hessian2Input.error(Hessian2Input.java:2720) ~[dubbo-2.8.4a.jar:2.8.4a]
at com.alibaba.com.caucho.hessian.io.Hessian2Input.expect(Hessian2Input.java:2691) ~[dubbo-2.8.4a.jar:2.8.4a]
at com.alibaba.com.caucho.hessian.io.Hessian2Input.readInt(Hessian2Input.java:773) ~[dubbo-2.8.4a.jar:2.8.4a]
at com.alibaba.dubbo.common.serialize.support.hessian.Hessian2ObjectInput.readInt(Hessian2ObjectInput.java:58) ~[dubbo-2.8.4a.jar:2.8.4a]
at com.alibaba.dubbo.rpc.protocol.dubbo.DecodeableRpcInvocation.decode(DecodeableRpcInvocation.java:106) ~[dubbo-2.8.4a.jar:2.8.4a]
显然，因为版本差异造成了向下兼容有问题，那怎么办呢，我首先想到的是把消费端的dubbo starter也升级到2.8.4，但这个版本不是阿里做的，所以阿里官方的starter还是稳稳的停留在2.0.0的最新版本，只支持dubbo 2.6.0的版本，那怎么办呢？
2、看山不是山，回归传统，不用starter
我其实首先尝试的是starter直接强行引用2.8.4的版本
<dependency>
<groupId>com.alibaba.spring.boot</groupId>
<artifactId>dubbo-spring-boot-starter</artifactId>
<version>2.0.0</version>
<exclusions>
<exclusion>
<groupId>com.alibaba</groupId>
<artifactId>dubbo</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>dubbo</artifactId>
<version>2.8.4</version>
</dependency>可惜可耻的失败了，启动消费端的时候就报错了
12:12:01.733 [main] ERROR org.springframework.boot.SpringApplication - Application run failed
java.lang.NoClassDefFoundError: com/alibaba/dubbo/qos/server/DubboLogo
at com.alibaba.dubbo.spring.boot.context.event.DubboBannerApplicationListener.buildBannerText(DubboBannerApplicationListener.java:49)
at com.alibaba.dubbo.spring.boot.context.event.DubboBannerApplicationListener.onApplicationEvent(DubboBannerApplicationListener.java:39)
at com.alibaba.dubbo.spring.boot.context.event.DubboBannerApplicationListener.onApplicationEvent(DubboBannerApplicationListener.java:23)
at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:127)
at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:76)
at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:53)
at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:345)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:308)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215)
at com.skyblue.dubbodemo.DubbodemoClientApplication.main(DubbodemoClientApplication.java:13)这里有一个DubboLogo的报错，后面我们会讲到。显然，starter里面用到的dubbo2.6.0的代码在dubbo2.8.4里面做了改动，已经调不了了，怎么办，只能抛弃starter，使用传统的dubbo调用方法了。
//不使用starter
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>dubbo</artifactId>
<version>2.8.4</version>
</dependency>在resources/spring目录下添加一个dubbo-consumer.xml文件
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://code.alibabatech.com/schema/dubbo
http://code.alibabatech.com/schema/dubbo/dubbo.xsd">
<dubbo:application name="mydubbodemo"/>
<!-- 注册中心配置，使用zookeeper注册中心暴露服务地址 -->
<dubbo:registry id="registry1" address="zookeeper://127.0.0.1:2181" timeout="60000" />
<dubbo:consumer timeout="120000" retries="0" check="false"/>
<dubbo:reference interface="com.skyblue.dubbodemo.service.IHelloService" registry="registry1" id="helloService"/>
</beans>然后在消费端的启动文件里面加上这个xml文件
@SpringBootApplication
@ImportResource("classpath:spring/dubbo-consumer.xml")
class DubbodemoClientApplication{
public static void main(String[] args) {
SpringApplication.run(DubbodemoClientApplication.class, args);
}
}调用服务的类改成传统的引入方式
@Autowired
private IHelloService helloService;这样就能使用2.8.4版本的dubbo了。
但是，这种方法需要在xml里面显式的申明我需要调用的服务，和直接用注解@Reference就调用服务比方便性差太多了，虽然现在可以使用了，但我还是深深的想念starter...
3、看山还是山，就要用starter
看过我之前文章的朋友应该清楚，其实starter是一个很简单的规范，可以让开发人员来自定义自己的starter，既然官方不支持，那我们就自己改一个starter不就行了，我就是拿2.0.0版本的官方dubbo starter改的。先clone一份官方的版本，这里。
首先要改的就是把pom.xml的dubbo版本升级到2.8.4，但改完后就会看到有报错。报错就是这个类DubboBannerApplicationListener
bannerTextBuilder.append(DubboSpringBootStarterConstants.LINE_SEPARATOR).append(DubboLogo.dubbo)
.append(" :: Dubbo :: (v").append(Version.getVersion()).append(")")
.append(DubboSpringBootStarterConstants.LINE_SEPARATOR);里面的DubboLogo这个类在dubbo后面版本里面被去掉了，所以报错，但这个其实是在后台的console 出现一个dubbo的标志，不要也无所谓，去掉就好了。上面我们在消费端强行升级dubbo版本，启动时报的其实也是这个错。
然后我们再次改pom.xml文件，把spring boot和jdk的版本也升一下
<properties>
...
<java.version>1.8</java.version>
<spring-boot.version>2.2.1.RELEASE</spring-boot.version>
<dubbo.version>2.8.4a</dubbo.version>
...
</properties>这样，一个可以在2.8.4a版本下使用的dubbo starter就改造完成了。
4、用起来
虽然改完了，但怎么用却还是一个问题，第一种方法是直接用mvn package生成dubbo-spring-boot-starter-2.8.4a.jar，然后copy到项目中去。但这种方法在现在的软件开发中已经不常用了，大部分用的方法是发布到maven的nexus私服。首先要把pom.xml改一下
<distributionManagement>
<snapshotRepository>
<id>snapshots</id>
<url>http://私服ip:port/nexus/content/repositories/snapshots</url>
</snapshotRepository>
<repository>
<id>releases</id>
<url>http://私服ip:port/nexus/content/repositories/releases</url>
</repository>
</distributionManagement>另外本地maven软件的setting.xml文件也要配置一下：
<servers>
<server>
<id>releases</id>
<username>账号</username>
<password>密码</password>
</server>
<server>
<id>snapshots</id>
<username>admin</username>
<password>admin123</password>
</server>
</servers>然后执行 mvn deploy就能发布到私服上去了。如果deploy有报这个错
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-gpg-plugin:1.6:sign (sign-artifacts) on project dubbo-spring-boot-starter: Unable to execute gpg command: Error while executing process. Cannot run program "gpg.exe": CreateProcess error=2, 系统找不到指定的文件。 -> [Help 1]
是因为deploy的时候调用了gpg的签名，我们私服不见得需要，我直接把它从pom.xml里面去掉了
<plugin>
<artifactId>maven-gpg-plugin</artifactId>
<version>${maven-gpg-plugin.version}</version>
<configuration>
<skip>false</skip>
</configuration>
<executions>
<execution>
<id>sign-artifacts</id>
<phase>verify</phase>
<goals>
<goal>sign</goal>
</goals>
</execution>
</executions>
</plugin>就是这段，去掉后，发布成功就能够直接在项目的pom.xml中引用了。
修改后的starter源代码