从4.2.0.RC3升级到4.2.0.RELEASE时出现Spring Async问题
问题内容：
我有一个使用spring（4.2.x）工件的Web应用程序spring-webmvc，spring-messaging，spring-websocket
我在spring config java类中具有以下@ Enable *批注
@EnableWebMvc
@EnableWebSocketMessageBroker
@EnableAsync
@EnableMBeanExport
WebSocket用于将消息广播到浏览器客户端。几乎没有用@Async注释的异步方法
该应用程序在Spring
4.2.0.RC3版本上运行良好。但是，当我将其更改为GA版本4.2.0.RELEASE时，启动时出现以下异常。如果我删除@EnableAsync，它可以正常工作，但是我需要异步功能。
org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [org.springframework.core.task.TaskExecutor] is defined: expected single matching bean but found 4: clientOutboundChannelExecutor,messageBrokerTaskScheduler,clientInboundChannelExecutor,brokerChannelExecutor
org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:366)
org.springframework.beans.factory.support.DefaultListableBeanFactory.getBean(DefaultListableBeanFactory.java:332)
org.springframework.scheduling.annotation.AsyncAnnotationBeanPostProcessor.setBeanFactory(AsyncAnnotationBeanPostProcessor.java:128)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeAwareMethods(AbstractAutowireCapableBeanFactory.java:1597)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1565)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:545)
org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:305)
org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:301)
org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:201)
org.springframework.context.support.PostProcessorRegistrationDelegate.registerBeanPostProcessors(PostProcessorRegistrationDelegate.java:228)
org.springframework.context.support.AbstractApplicationContext.registerBeanPostProcessors(AbstractApplicationContext.java:682)
org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:522)
org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:667)
org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:539)
org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:493)
org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:136)
问题答案：
你的一个中@Configuration必须实现AsyncConfigurer指定特定TaskExecutor的@Async方法。
否则，将会使从中选择哪个混淆applicationContext。
即使可以正常使用RC3也没关系，因此该错误已针对进行了修复GA。
更新
源代码AsyncAnnotationBeanPostProcessor如下所示：
Executor executorToUse = this.executor;
if (executorToUse == null) {
try {
// Search for TaskExecutor bean... not plain Executor since that would
// match with ScheduledExecutorService as well, which is unusable for
// our purposes here. TaskExecutor is more clearly designed for it.
executorToUse = beanFactory.getBean(TaskExecutor.class);
}
catch (NoUniqueBeanDefinitionException ex) {
try {
executorToUse = beanFactory.getBean(DEFAULT_TASK_EXECUTOR_BEAN_NAME, TaskExecutor.class);
}
catch (NoSuchBeanDefinitionException ex2) {
throw new IllegalStateException("More than one TaskExecutor bean exists within the context, " +
"and none is named 'taskExecutor'. Mark one of them as primary or name it " +
"'taskExecutor' (possibly as an alias); or specify the AsyncConfigurer interface " +
"and implement getAsyncExecutor() accordingly.", ex);
}
}
catch (NoSuchBeanDefinitionException ex) {
logger.debug("Could not find default TaskExecutor bean", ex);
// Giving up -> falling back to default executor within the advisor...
}
}
因此，我想在从RC3迁移到GA之前，您已经taskExecutor对此事有所了解。
正如您在StackTrace上看到的那样，已经有一个这样的bean …
