java.lang.ClassCastException While Using Projection in hibernate 4

Question

I am using hibernate to fetch only specific fields from and Entity. For that I am using Criteria API and using projections. I am getting ClassCastExcepiton when I try to traverse the list returned by the list() method of the Criteria API.

Please help me in finding out the missing of the below code.

@RequestMapping("/pResult")
public String retrieveLpnOnPagination(Model model) {

    for (int i = 1; i <= 9; i += 3) {
        List<MyLpn> lpns = lpnService.retrievePaginatedResult(i, 3,new String[]{"lpnId","status","whse"});
        for (MyLpn lpn : lpns)
            System.out.println(lpn.toString());
        System.out.println();
    }
    return "home";
}

DaoImpl method

public List<MyLpn> retrievePResult(int i, int j, String[] projectionFields) {
    Session currentSession = sessionFactory.getCurrentSession();
    Criteria createCriteria = currentSession.createCriteria(MyLpn.class);
    ProjectionList projectionList = Projections.projectionList();
    for (String field : projectionFields)
        projectionList.add(Projections.property(field));
    createCriteria.setProjection(projectionList);
    List<MyLpn> list = createCriteria.list();
    for (MyLpn lpn : list)
        System.out.println(lpn.toString());
    return list;
}

Exception

SEVERE: Servlet.service() for servlet [spring] in context with path [/MyW2014] threw exception [Request processing failed; nested exception is java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.w.model.MyLpn] with root cause
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.w.model.MyLpn
    at com.wmos.dao.LpnDaoImpl.retrievePResult(LpnDaoImpl.java:88)
    at com.w.service.LpnService.retrievePaginatedResult(LpnService.java:43)
    at com.wmos.service.LpnService$$FastClassBySpringCGLIB$$4e814eab.invoke(<generated>)
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:720)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:281)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:655)
    at com.wmos.service.LpnService$$EnhancerBySpringCGLIB$$bec224d4.retrievePaginatedResult(<generated>)
    at com.wmos.controller.LpnController.retrieveLpnOnPagination(LpnController.java:57)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:222)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:814)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:737)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:969)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:860)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:845)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:494)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:1025)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1136)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)

Thank you.

Well ofcourse it fails. You use a projection. So instead of getting the MyLpn you now get the result of the projection. Which is an object[] in your case containing the projected fields. — M. Deinum
– M. Deinum, Commented Aug 16, 2018 at 5:39

Nikolai Shevchenko · Accepted Answer · 2018-08-16 05:12:19Z

3

Try this

createCriteria.setResultTransformer(Transformers.aliasToBean(MyLpn.class));
List<MyLpn> list = createCriteria.list();

answered Aug 16, 2018 at 5:12

Nikolai Shevchenko

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