Btukfyl

I am getting the following error "Ljava.lang.Object; cannot be cast to com.entity.MechanicEntity" when trying to fetch the list of mechanic rows from database and pass to the jsp page.

Mechanic Entity

@Entity

@Table(name="Mechanic")

public class MechanicEntity {

@Id

@GeneratedValue(strategy=GenerationType.AUTO)



int mechanicId;

String mechanicType;

int numberOfVehicles;

public int getMechanicId() {

    return mechanicId;

}

public void setMechanicId(int mechanicId) {

    this.mechanicId = mechanicId;

}

public String getMechanicType() {

    return mechanicType;

}

public void setMechanicType(String mechanicType) {

    this.mechanicType = mechanicType;

}

public int getNumberOfVehicles() {

    return numberOfVehicles;

}

public void setNumberOfVehicles(int numberOfVehicles) {

    this.numberOfVehicles = numberOfVehicles;

}



}

RegisterController.java

...

RegisterService service;

 @ModelAttribute("MechList")

 public Map<Integer,Integer> populateMechId()throws Exception {



    List<Mechanic> allMech = service.getAllMechanic();

    Map<Integer,Integer> MechanicMap=new HashMap<Integer,Integer>();



    for(Mechanic mechanic:allMech){

        MechanicMap.put(mechanic.getMechanicId(),mechanic.getMechanicId());

    }



    return MechanicMap;

}  ...

RegisterService.java

...

RegisterDAO dao;

public List<Mechanic> getAllMechanic() throws Exception

{

  return dao.getAllMechanic();

}

...

RegisterDAO.java

public List<Mechanic> getAllMechanic() throws Exception

{

    List<Mechanic> mlist=new ArrayList<Mechanic>();

    Query q=em.createQuery("select m.mechanicId,m.mechanicType from MechanicEntity m");

    List<MechanicEntity> l1=q.getResultList();

    for(MechanicEntity m:l1)

    {

        Mechanic mechanic=new Mechanic();

        mechanic.setMechanicId(m.getMechanicId());

        mlist.add(mechanic);



    }

    return mlist;

}

registerVehicle.jsp

<form:form name="registerForm1"  action="registerVehicle.htm"  modelAttribute="serviceregister" method="GET" >

<form:select path="mechanicId">

<form:options items="${MechList}" />

</form:select>

</form:form>

Error:

Type Exception Report



Message org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.entity.MechanicEntity



Description The server encountered an unexpected condition that prevented it from fulfilling the request.



Exception 

org.apache.jasper.JasperException: org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.entity.MechanicEntity

    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:594)

    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:495)

    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)

    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)

    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)

    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)







Root Cause 

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.entity.MechanicEntity

    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:978)

    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)

    javax.servlet.http.HttpServlet.service(HttpServlet.java:624)

    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)

    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)

    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

    org.apache.jasper.runtime.PageContextImpl.doForward(PageContextImpl.java:750)

    org.apache.jasper.runtime.PageContextImpl.forward(PageContextImpl.java:720)

    org.apache.jsp.index_jsp._jspService(index_jsp.java:92)

    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)

    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)

    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:472)

    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)

    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)

    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)

    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)







Root Cause 

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.entity.MechanicEntity

    com.dao.RegisterDAO.getAllMechanic(RegisterDAO.java:19)

    com.service.RegisterService.getAllMechanic(RegisterService.java:27)

    com.controller.RegisterController.populateMechId(RegisterController.java:40)

    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

    sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)

    sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

    java.lang.reflect.Method.invoke(Unknown Source)

    org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:163)

    org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:446)

    org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:434)

    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)

    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)

    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)

    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)

    javax.servlet.http.HttpServlet.service(HttpServlet.java:624)

    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)

    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)

    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

    org.apache.jasper.runtime.PageContextImpl.doForward(PageContextImpl.java:750)

    org.apache.jasper.runtime.PageContextImpl.forward(PageContextImpl.java:720)

    org.apache.jsp.index_jsp._jspService(index_jsp.java:92)

    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)

    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)

    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:472)

    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)

    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)

    javax.servlet.http.HttpServlet.service(HttpServlet.java:731)

    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

Please help me rectify it, so the dropdown is displayed when the view loads.

Your code doesn't even compile because of:

Query q=em.createQuery("select m.mechanicId,m.mechanicType from MechanicEntity m");

List<MechanicEntity> l1=q.getResultList();

The problem is that getResultList() return a List<Object> instead of List< MechanicEntity>.

To make it work:

 List<MechanicEntity> l1 = createQuery("select m from MechanicEntity m", MechanicEntity.class).getResultList();