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

Question

Here is the code:

public Users login(String username) {
        Users user=null;
        try {
            String hql="select user.name,user.password from Users user where user.name=:name";
            Query query = session.createQuery(hql);
            query.setString("name", username);
            user=(Users) query.list().get(0);
        } catch (HibernateException e) {
            e.printStackTrace();
        }
        return user;
    }

Error：

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.xl.entity.Users
    at com.xl.impl.HouseDaoImpl.login(HouseDaoImpl.java:51)
    at com.xl.biz.HouseBiz.login(HouseBiz.java:25)
    at com.xl.Servlet.UserServlet.doGet(UserServlet.java:25)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:261)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:581)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
    at java.lang.Thread.run(Thread.java:619)

(Translations courtesy Google Translate)

What is the question? You might want to consider looking at the help page for some examples on what to include in your questions. Welcome to SO. — Qben
– Qben, Commented Sep 3, 2013 at 5:23

Ean V · Accepted Answer · 2013-09-03 06:13:31Z

3

If you need the Users object, edit your query to be like

String hql="from Users user where user.name=:name";

Otherwise the result will be an array of objects so you need to either use a transformer or simply cast it to object[]:

String hql="select user.password from Users user where user.name=:name";
Query query = session.createQuery(hql);
query.setString("name", username);
Object[] result =(Object[]) query.list().get(0);
String password = result[0];

answered Sep 3, 2013 at 6:13

Ean V

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Comments

Alex · Accepted Answer · 2013-09-03 05:36:10Z

1

You can create another constructor for Users as public Users(String name, String password) and change query to

String hql="select new yourpath.Users(user.name,user.password) from Users user
where user.name=:name";

edited Sep 3, 2013 at 5:36

answered Sep 3, 2013 at 5:22

Alex

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Luca Basso Ricci · Accepted Answer · 2013-09-03 06:07:19Z

1

You need a ResultTransformer backed on root entity in this manner

Query query = session.createQuery(hql);
query.setResultTransformer(RootEntityResultTransformer.INSTANCE);
query.list()

Using a projection (the select list) will produce a result of Object[] type: the ResultTransformer will create a User object and maps raw Object[] to correct User's property

edited Sep 3, 2013 at 6:07

answered Sep 3, 2013 at 5:50

Luca Basso Ricci

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Comments

Gaurav Gupta · Accepted Answer · 2013-09-03 05:34:30Z

-1

Since query.list() returns List, and here you are casting the content of the list to type User, Now, as exception says Object can not be cast to User. Please make sure, are you getting the content in form of user.

You can make a check:

 if(query.list() instanceOf User){
        // can cast to user.
 }else{
        // can not cast to User.
 }

answered Sep 3, 2013 at 5:34

Gaurav Gupta

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1 Comment

Alex Over a year ago

No need to do it, hql should be just fixed or return different data type.

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