java.lang.ClassCastException:无法强制转换java.lang.Integer

Question

当我点击登录时,它检查数据库是否有值匹配然后我得到这个错误,否则它打印我null.

public Login authenticate(Login login) {
         String query = "SELECT 1 FROM Login AS l WHERE l.email=? AND l.password=?";
         Object[] parameters = { login.getEmail(), login.getPassword() };
         List resultsList = getHibernateTemplate().find(query,parameters);
         if (resultsList.isEmpty()) {            
         }
         else if (resultsList.size() > 1) {

         }
         else {
           Login login1 = (Login) resultsList.get(0);
           System.out.println("Hello" + login1);
           return login1;
         }       
       return null;  
}

错误如下

原因:java.lang.ClassCastException:java.lang.Integer无法在com.vaadin.event.EventRouter的com.vaadin.event.ListenerMethod.receiveEvent(ListenerMethod.java:507)中强制转换为com.intermedix.domain.Login. fireEvent(EventRouter.java:161)at com.vaadin.ui.AbstractComponent.fireEvent(AbstractComponent.java:1154)at com.vaadin.ui.Button.fireClick(Button.java:371)at com.vaadin.ui.Button .changeVariables(Button.java:193)在com.vaadin.terminal.gwt.server.AbstractCommunicationManager.handleVariables(AbstractCommunicationManager.java:1094)在com.vaadin.terminal.gwt.server.AbstractCommunicationManager.doHandleUidlRequest(AbstractCommunicationManager.java:590 )在com.vaadin.terminal.gwt.server.CommunicationManager.handleUidlRequest(CommunicationManager.java:266)在com.vaadin.terminal.gwt.server.AbstractApplicationServlet.service(AbstractApplicationServlet.java:476)在javax.servlet.http包. HttpServlet.service(HttpServlet.java:820)在org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.j)ava:511)org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:390)org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)atg.mortbay.jetty.servlet .sessionHandler.handle(SessionHandler.java:182)org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765)atg.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418)at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)在org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)在org.mortbay.jetty.handler.HandlerWrapper.handle( HandlerWrapper.java:152)org.mortbay.jetty.Server.handle(Server.java:326)org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)atg.mortbay.jetty.HttpConnection $ RequestHandler .content(HttpConnection.java:943)位于org.mortbay的org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:756)org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218).orm.mortbay.thread.QueuedThreadPool上的org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)中的jetty.HttpConnection.handle(HttpConnection.java:404)$ PoolThread.run(QueuedThreadPool.java:582)引起:java.lang.ClassCastException:java.lang.Integer无法在sun.reflect.NativeMethodAccessorImpl.invoke0的com.intermedix.services.LoginService.authenticate(LoginService.java:34)中强制转换为com.intermedix.domain.Login. (本地方法)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)at java.lang.reflect.Method.invoke(Method.java:597) )org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:301)org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)at org.springframework.aop.framework.ReflectiveMethodInvocation.继续(ReflectiveMethodInvocation.java:149)a 吨org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)在org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)在org.springframework.aop.framework.JdkDynamicAopProxy.invoke (JdkDynamicAopProxy.java:204)在$ Proxy32.authenticate(未知来源)的com.intermedix.ui.LoginDailog.checkLogin(LoginDailog.java:106)com.intermedix.ui.LoginDailog.access $ 0(LoginDailog.java:102) )在com.intermedix.ui.LoginDailog $ 1.buttonClick(LoginDailog.java:52)在sun.reflect.NativeMethodAccessorImpl.invoke0(本机方法)在sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)在sun.reflect .delegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)at java.lang.reflect.Method.invoke(Method.java:597)at com.vaadin.event.ListenerMethod.receiveEvent(ListenerMethod.java:487)... 26更多

Answer 1

也许你想要SELECT l(L字母)而不是SELECT 1(数字1)？选择数字时,将返回该数字.因此Integer

或者,如果这1是限制,那么使用query.setMaxResults(1)