Data from HSQLDB table into two dimensional array using Java

Question

I am trying to get data from LivEx table as list, and then save that data into two dimensional array called array. My method is returning object[][].

I made up this code from googling here and there and taking bits from every example, however I am doing something wrong which I can't quite seem to put my finger on. It gives me an exception which is a NullPointerException whenever I call getLivExList(currentPlan).

Here is my code:

public static Object[][] getLivExList(String currentPlan) throws Exception {
    Session s = null;

    try {
        s = HibernateUtil.getSessionFactory().getCurrentSession();
        s.beginTransaction();
        String query = "select F.item, F.category, F.amount from LivEx F where F.planName=?";
        Query q = s.createQuery(query);
        System.out.println(query);
        List fp = q.list();
        s.getTransaction().commit();
        Object array[][] = new Object[fp.size()][3];
        for (int i = 0; i < fp.size(); i++) {
            for (int j = 0; j < 3; j++) {
                array[i][j] = fp.get(j +(3 * i));
            }
        }
         System.out.println("getLivExdata in networthentitymanager OKAY");
        return array;
    } catch (Exception e) {
         System.out.println("problem at getLivExdata in networthentitymanager");
         throw e;
    } finally {
        if (s != null) {
            HibernateUtil.closeSession();
        }
    }

Please help me find out where the problem is coming from.

This is the exception I am getting:

    SEVERE: null
    org.hibernate.QueryException: Expected positional parameter count: 1, actual parameters: [] [select F.item, F.category, F.amount from LivEx F where F.planName=?]
    0 problem 
    at org.hibernate.impl.AbstractQueryImpl.verifyParameters(AbstractQueryImpl.java:319)
    at org.hibernate.impl.AbstractQueryImpl.verifyParameters(AbstractQueryImpl.java:275)
    at org.hibernate.impl.QueryImpl.list(QueryImpl.java:75)
    at com.elitconsultancy.finplanner.entity.NetWorthEntityManager.getLivExList(NetWorthEntityManager.java:213)

We aren't psychic... Please indicate which line of the code you posted you are getting the NPE, eg insert a line before saying // NPE on next line — Bohemian
– Bohemian ♦, Commented Oct 24, 2011 at 5:13
@Bohemian check the edit please that is the exception i am getting — Precious
– Precious, Commented Oct 24, 2011 at 5:32
To be brutally honest: if you build this by "googling here and there and taking bits from every example" then that part is what you're doing wrong: You must learn about the technology you are using and not simply string together parts of (probably half-wrong) examples all around the web. That's a surefire way to disaster. — Joachim Sauer
– Joachim Sauer, Commented Oct 24, 2011 at 6:31
Query.list() will return a List<Object[]>. fp.get(j +(3 * i)) is wrong. It should be ((Object[]) fp.get(i))[j] — JB Nizet
– JB Nizet, Commented Oct 24, 2011 at 6:33
I agree with Joachim. Hibernate has an extremely well written reference documentation, which is exhaustive and full of examples. Read it. docs.jboss.org/hibernate/core/3.6/reference/en-US/html_single — JB Nizet
– JB Nizet, Commented Oct 24, 2011 at 6:35

Joachim Sauer · Accepted Answer · 2011-10-24 06:07:28Z

2

You're not setting the plan name for the query, even 'though you've specified a positional parameter (?).

Put this before your call to list:

query.setString(0, currentPlan);

answered Oct 24, 2011 at 6:07

Joachim Sauer

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Zohaib · Accepted Answer · 2011-10-24 05:13:35Z

0

List fp = q.list();         
s.getTransaction().commit();         
Object array[][] = new Object[fp.size()][3];

you are getting size of list. If list returned by q.list() is null, that is no matching rows found then you will get Null pointer exception.

Thats the first thing i see that might be wrong in the code

before invoking methods on list, u can check whether it is null or not.

answered Oct 24, 2011 at 5:13

Zohaib

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2 Comments

JB Nizet Over a year ago

-1. Query.list() never returns null, as should any method returning a List. And this is not the cause of the exception. Just read the message from the exception.

Zohaib Over a year ago

@JBNizet stack trace was not available when I answered the question...anyways thanks for pointing out

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