String concatenation in select clause

razzi · **Joined:** Tue Aug 26, 2003 9:29 am **Posts:** 12

Currently it is not possible to use something like

Code:

select object.str1 || object.str2 || object.str3 from MyClass as object

Is there a easy workaround (yes, I know there are, but I want to have just ONE result back instead of 3 because of a design issue) or are there any plans to implement this functionality???

Thanks

gavin · **Posted:** Wed Nov 19, 2003 12:12 pm

There are plans already in action to reimplement HQL using a new ANTLR parser. Perhaps in that timeline (Hibernate 2.2)

mnickel · **Joined:** Wed Nov 12, 2003 11:16 am **Posts:** 9

This is an interesting question as I've come across something similar. Instead of concatenation, I was trying to perform some mathematical functions on the properties from a queried Object:

Code:

select obj.a, obj.b, (obj.a + obj.b) from Object obj

This fails from Hibernate, so what I've done is include the calculation in my DAO layer. So my Business Layer will see a List that has a, b, and (a+b).

a little code snippet from my DAO

Code:

Iterator it = queryresultlist.iterator();
while(it.hasNext()) {
  List newvallist = new ArrayList();
  a = 0;
  b = 0;
         
  Object[] vals = (Object[])it.next();
  for( int i=0; i< vals.length; i++) {
           newvallist.add(vals[i]);
           if( i == 0 ){
                a = new Integer( vals[i].toString() ).intValue();
           }
           if( i == 1 ){
                b = new Integer( vals[i].toString()).intValue();
           }
  }
         
  Integer tot = new Integer( (a+b) );
  newvallist.add(tot);

  newqueryresultlist.add(newvallist.toArray());
}

return newqueryresultlist;

IMHO, if you haven't learned about DAO as part of a design pattern, you really should search in this forum for DAO threads... very enlightnening. It will make your code much more portable and flexible.

michael · **Posted:** Wed Nov 19, 2003 12:18 pm

It would be cool if we could do something like this:

Code:

select new StringBuffer(object.str1).append(object.str2).append(object.str3).toString() from MyClass as object

Don't panic :)

razzi · **Joined:** Tue Aug 26, 2003 9:29 am **Posts:** 12

Got a solution by defining an object

Code:

class MyClass {
   private String str1;
   private String str2;
   private String str3;

   public MyClass (String str1,String str2, String str3);
      this.str1 = str1;
      this.str2 = str2;
      this.str3 = str3;
   }

   public String toString() {
        return str1+ str2+ str3;
    }
}

and then:

Code:

select new MyClass(str1,str2,str3) from MyClass as object

works, but returns 3 times the Object instead of one (is there a bug in the parser maybe, because of the ',' ) ???

Thanks

razzi · **Joined:** Tue Aug 26, 2003 9:29 am **Posts:** 12

Correction: I mean

Code:

select new MyClass(object.str1,object.str2,object.str3) from MyClass as object

but still the same - a List of Object[3] rows instead of a List of Objects

p.s. Hibernate stable latest 2.0.3
[/code]

razzi · **Joined:** Tue Aug 26, 2003 9:29 am **Posts:** 12

Anyone an idea???

david · **Posted:** Thu Nov 20, 2003 10:30 pm

You have three records in the table. Maybe.

gavin · **Posted:** Thu Nov 20, 2003 10:38 pm

I don't believe you.

If you can reproduce this in a VERY simple main method (I mean like one persistent class with 3 properties and a main method), submit it to JIRA.

But I think you are mistaken.

razzi · **Joined:** Tue Aug 26, 2003 9:29 am **Posts:** 12

I'll try that later

- for your info - the select has been done using hibern8ide-0.9; maybe it's a bug in that tool

razzi · **Joined:** Tue Aug 26, 2003 9:29 am **Posts:** 12

Just to confirm it works fine using my suggestion - the bug was related to hibern8ide...

max · **Posted:** Mon Dec 08, 2003 2:49 pm

razzi wrote:

I'll try that later

- for your info - the select has been done using hibern8ide-0.9; maybe it's a bug in that tool

A bug in hibern8ide - no way! ;)

It should just return a list of MyClass objects - but i doesn't, or ?