1

Code:

public void getDetails() {
try {
Session session = sessionFactory.openSession();
Transaction transaction = session.beginTransaction();
String hql = "select c.mobile, c.password FROM CrbtSubMasterDemo c where rownum<20";
Query query = session.createQuery(hql);
List<CrbtSubMasterDemo> itr = query.list();
session.getTransaction().commit();
for (CrbtSubMasterDemo pojo : itr) {//excepion line
System.out.println("[" + pojo.getMobile() + "]");
}
} catch (Exception e) {
e.printStackTrace();
}
}

CrbtSubMasterDemo is pojo mapped with the db. When I try to run it, it gives following Exception:

java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.telemune.demoPojo.CrbtSubMasterDemo
at com.telemune.demoHibernate.QueryTester.getDetails(QueryTester.java:57)
at com.telemune.demoHibernate.QueryTester.main(QueryTester.java:23)

The question is query.list() is returning the list of objects of pojo class. Then why is this Exception. I am new to Hibernate, sorry if its a silly question.

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1
  • @ v.ladynev please help sir. Commented Apr 27, 2016 at 8:06

4 Answers 4

Reset to default
3

When you write this:

String hql = "select c.mobile, c.password FROM CrbtSubMasterDemo c where rownum<20";

Your result set is not a List of CrbtSubMasterDemo

Try to write:

String hql = "select FROM CrbtSubMasterDemo c where rownum<20";

Another way is define a new constructor of CrbtSubMasterDemo where you pass only two fields c.mobile, c.password

so your query becomes:

String hql = "select new " + CrbtSubMasterDemo.class.getName() + "(c.mobile, c.password) FROM CrbtSubMasterDemo c where rownum<20";

If you follow this solution, remeber to add a default constructor too (without parameters), so in your pojo you have:

public CrbtSubMasterDemo(String mobile, String password) {
    this.mobile = mobile;
    this.password = password
}

and

public CrbtSubMasterDemo() {
}
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7 Comments

@ JoeTaras may be I am using it wrong but it turned into: ERROR: Unable to locate appropriate constructor on class [com.telemune.demoPojo.CrbtSubMasterDemo]. Expected arguments are: java.lang.String, java.lang.String Unable to locate appropriate constructor on class Expected arguments are: java.lang.String, java.lang.String
@yashpalbharadwaj You need to add a constructor with two String arguments to the CrbtSubMasterDemo. And you need a default constructor too.
@yashpalbharadwaj: I've updated my answer add a complete path of class. Another reaso can be if one of two fields are null. Yes, as has written v.ladynew, you must add a default constructor too (without parameters)
add space after new, sorry
If you want a variable number of fields yes, otherwise you can use the first solution (where you'll get all POJO rows, more expensely but is automapped)
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3 
String hql = "select c.mobile, c.password FROM CrbtSubMasterDemo c where rownum<20";
Query query = session.createQuery(hql);

Result of this will be List<Object[]>

List<Object[]> itr = query.list();

for (Object[] row : itr) {
  System.out.println(String.format("mobile:%s, password:%s", row[0], row[1]));
}

if mobile and password are strings, of course. You can use a transformer to transform results directly to CrbtSubMasterDemo.

Hibernate 3.2: Transformers for HQL and SQL

FluentHibernateResultTransformer

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2 Comments

yeah it worked...but can you please tell me.. what's the role of POJO it left with...I didn't use any getter of the class not even the object of pojo . How will I have the Idea that it is working on my POJO or not? thanks for help.
@yashpalbharadwaj Don't clear understand what you ask about. For a query from CrbtSubMasterDemo you will have a List<CrbtSubMasterDemo>. For a query select mobile, password FROM CrbtSubMasterDemo you will have a List<Object[]>.
1

Sir, Many times user faces this kinda requirements . Hibernate has ResultTransformer to convert a hql/sql in Object.

    public CrbtSubMasterDemo{
         private Stirng mobile;
         private String password;

          public CrbtSubMasterDemo(){
            --------------
         }

        #####after setting the transation set whichever columns you are selecting should be given as name of property of your object
        String hql = "select c.mobile as mobile, c.password as password FROM CrbtSubMasterDemo c where rownum<20";
        Query query = session.createQuery(hql);
        List<CrbtSubMasterDemo> itr = query.setResultTransformer(Transformers.aliasToBean(CrbtSubMasterDemo.class) ).list();
        ##No need to commit the transaction.
    }

It will convert you query into the CrbtSubMasterDemo

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6 Comments

this was a real solution by the way. Can you give me where I can Explore my Criteria/Hibernate concepts?
@ sunixi please explain why we are not commiting the transaction here
You can use Criteria where you want restrictions. Like Criteria cr = session.createCriteria(CrbtSubMasterDemo.class); cr.add(Restrictions.lt("rownum", 20)); List<CrbtSubMasterDemo> list=cr.list();
and yashpal ji criteria will return all coulumns of your table . If you want only selected columns shud be returned then you need to use Projections >
well..I hope we could have a chat box. but sunixi JI I asked 1. why we are not comming the transaction. 2.Can you give me where I can Explore my Criteria/Hibernate concepts. :) in refrence to ##No need to commit the transaction.
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1

Do not directly cast the result of "query.list();" to List of CrbtSubMasterDemo. As query.list() return object list. Iterate over the object list received and cast one by one to put in list List of CrbtSubMasterDemo

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