java.lang.ClassCastException : java. lang.Integer 无法转换

Question

当我点击登录时，它会检查数据库是否有匹配的值，然后我会收到此错误，否则它会打印我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;  
}

以下错误

Cause: java.lang.ClassCastException: java.lang.Integer cannot be cast to com.intermedix.domain.Login at com.vaadin.event.ListenerMethod.receiveEvent(ListenerMethod.java:507) at com.vaadin.event.EventRouter.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) at com.vaadin.terminal.gwt.server.AbstractCommunicationManager.handleVariables(AbstractCommunicationManager.java:1094) at com.vaadin.terminal.gwt.server.AbstractCommunicationManager.doHandleUidlRequest(AbstractCommunicationManager.java:590) at com.vaadin.terminal.gwt.server.CommunicationManager.handleUidlRequest(CommunicationManager.java:266) at com.vaadin.terminal.gwt.server.AbstractApplicationServlet.service(AbstractApplicationServlet.java:476) at javax.servlet.http.HttpServlet.service(HttpServlet.java:820) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:390) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418) at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230) at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:326) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542) at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:943) at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:756) at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404) at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410) at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582) Caused by: java.lang.ClassCastException: java.lang.Integer cannot be cast to com.intermedix.domain.Login at com.intermedix.services.LoginService.authenticate(LoginService.java:34) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 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) at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:301) at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204) at $Proxy32.authenticate(Unknown Source) at com.intermedix.ui.LoginDailog.checkLogin(LoginDailog.java:106) at com.intermedix.ui.LoginDailog.access$0(LoginDailog.java:102) at com.intermedix.ui.LoginDailog$1.buttonClick(LoginDailog.java:52) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 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) at com.vaadin.event.ListenerMethod.receiveEvent(ListenerMethod.java:487) ... 26 more

Answer 1

也许您想要SELECT l(L字母)而不是SELECT 1(数字1)？当您选择一个号码时，系统会返回该号码。因此整数

或者，如果此 1 意味着限制，则使用 query.setMaxResults(1)