Dubbo包编译版本较高导致项目启动失败

问题描述：

本地启动dubbo项目一直报错，错误信息如下

Caused by: java.lang.ExceptionInInitializerError
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
	at java.lang.reflect.Constructor.newInstance(Unknown Source)
	at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:100)
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:61)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:877)
	... 17 more
Caused by: java.lang.IllegalStateException: fail to create adaptive instance: java.lang.IllegalStateException: Can not create adaptive extenstion interface com.alibaba.dubbo.rpc.Protocol, cause: fail to create adaptive instance: java.lang.NoSuchMethodError: java.util.concurrent.ConcurrentHashMap.keySet()Ljava/util/concurrent/ConcurrentHashMap$KeySetView;
	at com.alibaba.dubbo.common.extension.ExtensionLoader.getAdaptiveExtension(ExtensionLoader.java:459)
	at com.alibaba.dubbo.config.ServiceConfig.(ServiceConfig.java:61)
	... 24 more
Caused by: java.lang.IllegalStateException: Can not create adaptive extenstion interface com.alibaba.dubbo.rpc.Protocol, cause: fail to create adaptive instance: java.lang.NoSuchMethodError: java.util.concurrent.ConcurrentHashMap.keySet()Ljava/util/concurrent/ConcurrentHashMap$KeySetView;
	at com.alibaba.dubbo.common.extension.ExtensionLoader.createAdaptiveExtension(ExtensionLoader.java:723)
	at com.alibaba.dubbo.common.extension.ExtensionLoader.getAdaptiveExtension(ExtensionLoader.java:455)
	... 25 more
Caused by: java.lang.IllegalStateException: fail to create adaptive instance: java.lang.NoSuchMethodError: java.util.concurrent.ConcurrentHashMap.keySet()Ljava/util/concurrent/ConcurrentHashMap$KeySetView;
	at com.alibaba.dubbo.common.extension.ExtensionLoader.getAdaptiveExtension(ExtensionLoader.java:459)
	at com.alibaba.dubbo.common.extension.ExtensionLoader.createAdaptiveExtensionClass(ExtensionLoader.java:738)
	at com.alibaba.dubbo.common.extension.ExtensionLoader.getAdaptiveExtensionClass(ExtensionLoader.java:732)
	at com.alibaba.dubbo.common.extension.ExtensionLoader.createAdaptiveExtension(ExtensionLoader.java:721)
	... 26 more
Caused by: java.lang.NoSuchMethodError: java.util.concurrent.ConcurrentHashMap.keySet()Ljava/util/concurrent/ConcurrentHashMap$KeySetView;
	at com.alibaba.dubbo.common.utils.ConcurrentHashSet.iterator(ConcurrentHashSet.java:48)
	at com.alibaba.dubbo.config.spring.extension.SpringExtensionFactory.getExtension(SpringExtensionFactory.java:44)
	at com.alibaba.dubbo.common.extension.factory.AdaptiveExtensionFactory.getExtension(AdaptiveExtensionFactory.java:47)
	at com.alibaba.dubbo.common.extension.ExtensionLoader.injectExtension(ExtensionLoader.java:533)
	at com.alibaba.dubbo.common.extension.ExtensionLoader.createAdaptiveExtension(ExtensionLoader.java:721)
	at com.alibaba.dubbo.common.extension.ExtensionLoader.getAdaptiveExtension(ExtensionLoader.java:455)
	... 29 more

问题原因：

maven依赖下载的dubbo包的编译JDK版本为1.8，而本地运行环境JDK版本为1.7，包的编译版本高于本地运行版本，所以出现上面错误，没仔细研究，很奇怪。

解决方法：

重新下载dubbo编译版本低的包即可。

注：

查看dubbo包JDK编译版本方法：

Build-Jdk即为编译该JAR的JDK版本，如果比运行环境高，可能会导致启动报上面的错误

本文完。