The bean 'llWebSocketHandler' could not be injected because it is a JDK dynamic proxy that implemen

摘要：在做Spring Boot、WebSockets整合的时候，出现了bean注入失败的问题，错误异常如下：

一：异常信息：

2018-08-10 11:44:50.072  WARN 20296 --- [           main] ationConfigEmbeddedWebApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'llWebSocketConfig': Unsatisfied dependency expressed through field 'llWebSocketHandler'; nested exception is org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'llWebSocketHandler' is expected to be of type 'com.micai.spring.messaging.web.socket.LlWebSocketHandler' but was actually of type 'com.sun.proxy.$Proxy57'
2018-08-10 11:44:50.075  INFO 20296 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2018-08-10 11:44:50.287  INFO 20296 --- [           main] utoConfigurationReportLoggingInitializer : 

Error starting ApplicationContext. To display the auto-configuration report re-run your application with 'debug' enabled.
2018-08-10 11:44:50.292 ERROR 20296 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

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APPLICATION FAILED TO START
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Description:

The bean 'llWebSocketHandler' could not be injected as a 'com.micai.spring.messaging.web.socket.LlWebSocketHandler' because it is a JDK dynamic proxy that implements:


Action:

Consider injecting the bean as one of its interfaces or forcing the use of CGLib-based proxies by setting proxyTargetClass=true on @EnableAsync and/or @EnableCaching.

其中最重要的一句就是：

The bean 'llWebSocketHandler' could not be injected as a 'com.micai.spring.messaging.web.socket.LlWebSocketHandler' because it is a JDK dynamic proxy that implements:

二：解决过程：

我们知道：spring.proxy-target-class属性值决定是基于接口的还是基于类的代理被创建。首先说明下proxy-target-class="true"和proxy-target-class="false"的区别，为true则是基于类的代理将起作用（需要cglib库），为false或者省略这个属性，则标准的JDK 基于接口的代理将起作用。
proxy-target-class在spring事务、aop、缓存这几块都有设置，其作用都是一样的。

所以要想解决上面的问题，只需要在application.properties文件中配置下spring.aop.proxy-target-class=true就行，这样LlWebSocketHandler类就可以被当做基于类的代理注入进来了。

以上就是对这个错误的分析过程。