get whole table from database

[shekhar john]

hello i m using jpa and struts2 and i am tring to get the two or more columns of database but it gives me this :-

[[Ljava.lang.Object;@77c909, [Ljava.lang.Object;@2f7965, [Ljava.lang.Object;@cad
f36, [Ljava.lang.Object;@1048900, [Ljava.lang.Object;@be7617, [Ljava.lang.Object
;@3ae26f, [Ljava.lang.Object;@1e82106, [Ljava.lang.Object;@d034c5]


my code is:-

public String execute(){

		EntityManagerFactory emf = Persistence
				.createEntityManagerFactory("tujpa");
		EntityManager em = emf.createEntityManager();
		EntityTransaction entr = em.getTransaction();
		entr.begin();
		mylist = new ArrayList();
		Query query = em.createQuery("select u.firstname,u.lastname from User u");
		List mylist = query.getResultList();
		System.out.println(mylist);
                entr.commit();
		em.close();
		return new DefaultHttpHeaders("create");

	}

please help me
thanks in advance

[Bosun Bello]

At what point in the code are you getting this error? You need to supply more information. That's probably why you did not get any responses yet.

[Ulf Dittmer]

It's not an error message, it's just that the object referenced by "myList" apparently does not have a terribly useful "toString" method defined. You'll have to print out each element of the list individually; since each element is apparently an array (probably of the two attributes you request), you'll need to take that into account as well.

[Tim Holloway]

As a rule, I don't recommend putting the ORM code directly in the web interface (Struts service) code. It's usually much cleaner to keep the persistency code isolated from the UI and business code. Besides, that code example can leak resources. One of the reasons why I prefer Spring for my persistency.

However, the real problem here is that you're not doing the query the way you think you are.

Standard approach would be like this:

List<User> findAllUser() {
....
         Query query = em.createQuery("select u from User u");  
         List mylist = query.getResultList();  
         return mylist;
}

Which would result in a list of all the user details.

When you only want selected columns, your code would work, subject to the observations I just made, but what the method is actually returning is a collection of Array objects, where each element of the collection is a 2-element Array of type Object, and the elements are a[0] = firstname, and a[1] = lastname. It's an Array of Object, because you can retrieve non-String columns this way as well, and Object is the lowest-common-denominator class.

There's a name for this kind of query in JPA, although I'd have to go back and look it up. It's not actually as useful or as as it looks, however, unless resources are tight. And the fact that the returned data is not strongly typed can lead to problems detectable only at runtime.

[Ravi Majety]

Ulf Dittmer wrote:It's not an error message, it's just that the object referenced by "myList" apparently does not have a terribly useful "toString" method defined. You'll have to print out each element of the list individually; since each element is apparently an array (probably of the two attributes you request), you'll need to take that into account as well.

I agree with this. It was not an error. Here it is returning the NestedList(ie., List containing the List objects. ) SO try to cast each object with an List and display them .

List<List> mylist = query.getResultList();

for(List mylist2 : mylist){
System.out.println("the values are "+mylist2.get(0)+" - "+mylist2.get(1));

}
System.out.println(mylist);
entr.commit();

Hope your problem is cleared???