Hello!

I have class Foo with three fields: 'a','b','c' and methods: setA, getA, setB, getB, setC, getC. when I create query "select a,b from Foo" I get Objet[2] as a result with Object[0]=a, and Object[1]=b. What I would like to achieve is to get instance of Foo with 'a' and 'b' fields properly set and empty 'c' (after query.iterate().next())

How am I supposed to do it?

Best Regards
Boloek

The only reason I could think one would want to slice an object like that is to avoid initializing the third field ("c" in your example) to save memory. If this is what you are trying to do, here is a link to the Lightweight Class pattern description - this pattern solves this problem by creating a lightweight superclass: http://www.hibernate.org/41.html.

Note that this pattern is useful only with Hibernate 2.x - you can achieve the same effect effortlessly and without the negative consequences in 3.x by using field-level lazy initialization. Using your example, you'd map "c" for lazy loading, and issue a query for the whole object. Hibernate 3.x will issue a query for a subset of fields that you didn't mark for lazy loading, giving you an object with only "a" and "b" set. Moreover, the code using the object will not notice that "c" is empty because it will be loaded on demand when you call getC().

I hope this helps.

actually I was thinking about performance issues. I have db table with 120 fields and I must scan it checking only few values. There are also extreme conditions when all values I use are indexed, so db engine does not have to get table data (only index values)
second thing is code/configuration bloat and possible mistakes when I have to put returned tuples into POJOs so I can write code: 'if (a.getValueX().equals(b.getValueY())', instead of meaningless 'if (taba[5].equals(tabb[3]))'
third: it is easy (in my approach and lazy loading one) to add field 'Foo' in HQL's select and right away use it few lines below by simple getFoo() statement. Though, lazy loading will need extra configuration...
Also I am afraid of "loading at demand" because I exactly know (at the moment of HQL statement) which fields I'll use so there is no need for any extra db queries

Please note that I'm new to hibernate :-)