背景

我在学习spring-cloud-alibaba技术栈期间，在学习服务熔断与限流的时候，服务启动发生了以下异常

#这是控制台最上面的

sun.misc.Unsafe.park(Native Method)

 java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)

 java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)

 java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1093)

 java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809)

 java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1074)

 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1134)

 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)

 java.lang.Thread.run(Thread.java:748)

#下面的是这样

Caused by: java.lang.AbstractMethodError: com.alibaba.cloud.sentinel.feign.SentinelContractHolder.parseAndValidateMetadata(Ljava/lang/Class;)Ljava/util/List;

	at feign.ReflectiveFeign$ParseHandlersByName.apply(ReflectiveFeign.java:151) ~[feign-core-10.7.4.jar:na]

	at feign.ReflectiveFeign.newInstance(ReflectiveFeign.java:49) ~[feign-core-10.7.4.jar:na]

	at feign.Feign$Builder.target(Feign.java:252) ~[feign-core-10.7.4.jar:na]

	at org.springframework.cloud.openfeign.HystrixTargeter.target(HystrixTargeter.java:38) ~[spring-cloud-openfeign-core-2.2.2.RELEASE.jar:2.2.2.RELEASE]

	at org.springframework.cloud.openfeign.FeignClientFactoryBean.loadBalance(FeignClientFactoryBean.java:253) ~[spring-cloud-openfeign-core-2.2.2.RELEASE.jar:2.2.2.RELEASE]

	at org.spring

framework.cloud.openfeign.FeignClientFactoryBean.getTarget(FeignClientFactoryBean.java:282) ~[spring-cloud-openfeign-core-2.2.2.RELEASE.jar:2.2.2.RELEASE]

	at org.springframework.cloud.openfeign.FeignClientFactoryBean.getObject(FeignClientFactoryBean.java:262) ~[spring-cloud-openfeign-core-2.2.2.RELEASE.jar:2.2.2.RELEASE]

	at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:171) ~[spring-beans-5.2.4.RELEASE.jar:5.2.4.RELEASE]

	... 33 common frames omitted

版本

 <properties>

        <java.version>1.8</java.version>

        <spring-cloud.version>Hoxton.SR3</spring-cloud.version>

        <spring-cloud-alibaba.version>2.2.0.RELEASE</spring-cloud-alibaba.version>

    </properties>

    <dependencyManagement>

        <dependencies>

            <dependency>

                <groupId>org.springframework.cloud</groupId>

                <artifactId>spring-cloud-dependencies</artifactId>

                <version>${spring-cloud.version}</version>

                <type>pom</type>

                <scope>import</scope>

            </dependency>

            <dependency>

                <groupId>com.alibaba.cloud</groupId>

                <artifactId>spring-cloud-alibaba-dependencies</artifactId>

                <version>${spring-cloud-alibaba.version}</version>

                <type>pom</type>

                <scope>import</scope>

            </dependency>

        </dependencies>

    </dependencyManagement>

最后发现这个问题是由于版本冲突造成的，because：spring-cloud版本不同，openfeign的版本也不同

修改spring-cloud版本为

<spring-cloud.version>Hoxton.SR1</spring-cloud.version>

运行项目

2020-03-07 23:25:53.279  INFO 12452 --- [1)-192.168.81.1] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring DispatcherServlet 'dispatcherServlet'

2020-03-07 23:25:53.279  INFO 12452 --- [1)-192.168.81.1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'

INFO: log output type is: file

INFO: log charset is: utf-8

INFO: log base dir is: C:\Users\taoym\logs\csp\

INFO: log name use pid is: false

2020-03-07 23:25:53.295  INFO 12452 --- [1)-192.168.81.1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 16 ms

测试服务熔断

总结

跟着官网的教程走，如果报错，那很有可能是版本的问题，多试几下就可以了！