Question

我遇到过这个问题。我已经成功地从JBoss中查找了我的远程bean，但是当我尝试调用它的任何方法时，下一个异常即将出现：

java.lang.Class cannot be cast to java.lang.String.

完整堆栈跟踪是：

java.lang.ClassCastException: java.lang.Class cannot be cast to java.lang.String
at org.jboss.ejb.client.remoting.ProtocolMessageHandler.readAttachments(ProtocolMessageHandler.java:56)
at org.jboss.ejb.client.remoting.InvocationExceptionResponseHandler$MethodInvocationExceptionResultProducer.getResult(InvocationExceptionResponseHandler.java:85)
at org.jboss.ejb.client.EJBClientInvocationContext.getResult(EJBClientInvocationContext.java:212)
at org.jboss.ejb.client.TransactionInterceptor.handleInvocationResult(TransactionInterceptor.java:47)
at org.jboss.ejb.client.EJBClientInvocationContext.getResult(EJBClientInvocationContext.java:214)
at org.jboss.ejb.client.ReceiverInterceptor.handleInvocationResult(ReceiverInterceptor.java:96)
at org.jboss.ejb.client.EJBClientInvocationContext.getResult(EJBClientInvocationContext.java:203)
at org.jboss.ejb.client.EJBClientInvocationContext.awaitResponse(EJBClientInvocationContext.java:341)
at org.jboss.ejb.client.EJBInvocationHandler.doInvoke(EJBInvocationHandler.java:126)
at org.jboss.ejb.client.EJBInvocationHandler.doInvoke(EJBInvocationHandler.java:107)
at org.jboss.ejb.client.EJBInvocationHandler.invoke(EJBInvocationHandler.java:90)
at com.sun.proxy.$Proxy32.createEvent(Unknown Source)
at com.mypackage.FacadeImpl.createEvent(FacadeImpl.java:89)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:201)
at com.sun.proxy.$Proxy28.createEvent(Unknown Source)

最后一行是调用我的方法＆＃34; CreateEvent＆＃34;。我猜这个例外是在＃34; getResult（）＆＃34; EJBClientInvocationContext的方法。

我的代码是：

IEventDao eventDao = (IEventDao) ctx.lookup("java:/task/EventDao!MyPackage.IEventDao");

EventDao已成功从远程获取。试图调用一个方法：

public Event createEvent(final Event event) {
    return eventDao.createEvent(event);
}

Event event = new EventImpl("Test event: Star Wars: Episode VI");
createEvent(event); <-- Line #89. Exception has been throwned.

CreateEvent方法体。但仅仅是为了您的信息：它甚至没有输入这段代码。它甚至在调用entityManager.persist(event);

之前就会抛出异常

@Transactional(propagation = Propagation.REQUIRED)
public Event createEvent(Event event) {
    entityManager.persist(event);
    return event;
}

以下是FacadeImpl的完整代码：

@Service
public class FacadeImpl implements BookingFacade {
@Autowired
private FacadeUtils facadeUtils;
private IEventDao eventDao;  
private InitialContext ctx;
private Properties props = new Properties();

public void init() throws NamingException, IOException {
    props.load(getClass().getResourceAsStream("/jndi.properties"));
    ctx = new InitialContext(props);
    eventDao = (IEventDao) ctx.lookup("java:/Assignment16-1.0-SNAPSHOT/EventDao!com.mypackage.IEventDao");      
}

public Event createEvent(final Event event) {
    return eventDao.createEvent(event);
}
}

Answer 1

大多数情况下，错误java.lang.ClassCastException: java.lang.Class cannot be cast to java.lang.String是由于使用泛型，或尝试向下转换（例如Object - ＆gt; String）为不兼容的类型。请记住，如果没有显式类型转换，则不能将Object类型分配给String类型，并且该对象应该可以转换为String。

这是排除ClassCastException问题的好帖子：http://examples.javacodegeeks.com/java-basics/exceptions/java-lang-classcastexception-how-to-solve-class-cast-exception/

调用EJB Bean方法时，不能将java.lang.Class强制转换为java.lang.String

1 个答案: