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Change update query for merge() in JPA

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hb_dev

Post subject: Change update query for merge() in JPA

Posted: Tue Dec 25, 2007 3:57 pm

Newbie

Joined: Mon Oct 15, 2007 11:44 am
Posts: 7

Hello,
I'm starting with JPA, so please help with basic JPA stuff !
In JPA, to update an entity (say customer) we use:

Code:

em.merge(customer);

1. What if I want to update ONLY certain fields ? (essentially i'm trying to change underlying UPDATE query for merge() method)

2. I have a field 'rowversion' which should be incremented when merge() called. How to do that ?
SQL query would have been:

Code:

UPDATE customer_table SET customer_city='city', rowversion=rowversion+1

Thank You.

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who_am_i

Post subject: Update fields

Posted: Fri Dec 28, 2007 8:27 am

Newbie

Joined: Wed Dec 26, 2007 9:36 am
Posts: 7

You have two options here (there might be some better way, I am pretty new to JPA/ORMs myself):

The first option has two steps (code is just to give you an idea):

Code:

// retreive the existing customer from db
Customer dbCustomer = em.findById...(customer.getId());
// update attributes you want to, and leave the rest
dbCustomer.setPhoneNr(customer.getPhoneNr);
dbCustomer.setRowVersion(dbCustomer.getRowVersion() + 1);
// save the updated customer
em.merge(dbCustomer);

The second option will involve running a sql/hsql query, pretty much on the same line as the query in your post.

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