java.lang.ClassCastException: [Ljava.lang.Object; and how to Convert the Class

Question

my DAO is

public class bookRequestStatusDAO {

    public static  List<Book> getbookRequest()
    {

           Session session=null;
           try
           {
                 List booklist=new ArrayList();

            session = HibernateUtil.getSession();
            System.out.println(" Session :: "+session);
            Query query=session.createSQLQuery("{call SP_bookRequestTable()}");
            booklist=query.list();
            System.out.println("in dao getrequest----"+booklist.size());
            if(booklist!=null)
            return booklist;
            else
                return new ArrayList();
           }
           catch(Exception e)
           {
               System.out.println("Exception in BookREqueststatus::"+e);
               return  null;
           }
           finally
           {
               session.close();

           }

    }

my Struts Action Class is

public ActionForward execute(ActionMapping mapping, ActionForm  form,
            HttpServletRequest request, HttpServletResponse response)
            throws Exception {
          System.out.println(" exce -----");
        BookrequeststatusForm bookrequeststatusForm=(BookrequeststatusForm)form;
        List<Book> convertlist=new ArrayList<Book>();
           convertlist=bookRequestStatusDAO.getbookRequest();


         System.out.println("list in Action::" +convertlist.size() );
          request.setAttribute("bookDeatils",convertlist );
        System.out.print("request in Action::"+request.getAttribute("bookDeatils"));
        return mapping.findForward(Constants.ACTION_FORWARD_SUCCESS);

    }
}

and in my jsp

<link rel="stylesheet" href="/REC_BookBank/css/bookRequestStatus.css">
<% 
   List<Book>list=new ArrayList<Book>();
    if(request.getAttribute("bookDeatils")!=null)
    {

        list = (ArrayList)request.getAttribute("bookDeatils");
            System.out.println("inside loop List --- "+list.size());
            for(Book book : list)
                {
                out.println("<tr><td>"+book.getId()+"</td></tr>");
            }
               }
    System.out.println(" List --- "+list.size());
%>

my Book.java

import java.io.Serializable;

/**
 *
 * @author Administrator
 */
public class Book implements Serializable {
 private String id;
 private String subject;
 private String title;
 private String author;
 private String publication;
 private String edition;
 private String status;
 private String mode;

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public String getEdition() {
        return edition;
    }

    public void setEdition(String edition) {
        this.edition = edition;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getMode() {
        return mode;
    }

    public void setMode(String mode) {
        this.mode = mode;
    }

    public String getPublication() {
        return publication;
    }

    public void setPublication(String publication) {
        this.publication = publication;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public String getSubject() {
        return subject;
    }

    public void setSubject(String subject) {
        this.subject = subject;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

}

in tomcat Consul

 exce -----
 Session :: SessionImpl(PersistenceContext[entityKeys=[],collectionKeys=[]];ActionQueue[insertions=[] updates=[] deletions=[] collectionCreations=[] collectionRemovals=[] collectionUpdates=[]])
Hibernate: {call SP_bookRequestTable()}
in dao getrequest----1
list in Action::1
request in Action::[[Ljava.lang.Object;@14ef239]inside loop List --- 1

Exception HTTP Status 500 -

---

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception in

org.apache.jasper.JasperException: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.rec.bookbank.persitencejavafile.Book
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:541)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:435)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)
    org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1085)
    org.apache.struts.tiles.TilesRequestProcessor.doForward(TilesRequestProcessor.java:263)
    org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:398)
    org.apache.struts.tiles.TilesRequestProcessor.processForwardConfig(TilesRequestProcessor.java:318)
    org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:241)
    org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
    org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)


root cause 

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.rec.bookbank.persitencejavafile.Book
    org.apache.jsp.jsp.bookRequestStatus_jsp._jspService(bookRequestStatus_jsp.java:82)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)
    org.apache.struts.action.RequestProcessor.doForward(RequestProcessor.java:1085)
    org.apache.struts.tiles.TilesRequestProcessor.doForward(TilesRequestProcessor.java:263)
    org.apache.struts.action.RequestProcessor.processForwardConfig(RequestProcessor.java:398)
    org.apache.struts.tiles.TilesRequestProcessor.processForwardConfig(TilesRequestProcessor.java:318)
    org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:241)
    org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
    org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:390)


note The full stack trace of the root cause is available in the Apache Tomcat/6.0.14 logs.

I need to print the value here, but it showing the Exception ClassCastException.

Answer 1

the reason why you are getting the exception is because the call to the stored procedure is returning an array of values which is not directly convertable to a class.. you can do one of the 2 things to get a list of books instead of list of object[].

• you can map the procedure in your .hbm.xml file & call it. (example)
• you can use a RowMapper class instance to map the rows. (this is something available in spring).

personally I'd prefer mapping the procedure, its a lot more elegant.

example to iterate :

// can be used in DAO to convert the object array into List of Objects
    public List<Book> getList(List<Object[]> bookResult){
    List<Book> books = new ArrayList<Book>();
    for(Object[] array:bookResult){
    Book book= new Book();
    book.setTitle(arr[0]); // you need to set the value of each pojo field here.
    books.add(book);
    }
    return books;
    }