Hibernate constraint ConstraintViolationException. Is there an easy way to ignore duplicate entries?

Basically I've got the below schema and I'm inserti开发者_如何学Gong records if they don't exists. However when it comes to inserting a duplicate it throws and error as I would expect. My question is whether there is an easy way to make Hibernate to just ignore inserts which would in effect insert duplicates?

CREATE TABLE IF NOT EXISTS `method` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(10) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `name` (`name`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=2 ;


SEVERE: Duplicate entry 'GET' for key 'name'
Exception in thread "pool-11-thread-4" org.hibernate.exception.ConstraintViolationException: could not insert:

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My question is whether there is an easy way to make Hibernate to just ignore inserts which would in effect insert duplicates?

How could Hibernate possibly know that a record has a non unique value without actually inserting the record?

If you are doing batch inserts and don't want to rollback the whole transaction and discard the session in case of a ConstraintViolationException (that's what you should do in theory after an exception, see this thread and this previous answer), my suggestion would be to use the StatelessSession API and to catch the ConstraintViolationException.

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Hibernate can't do this. You can however do it yourself. Essentially there are two options:

1. Check for duplicates before insert; or
2. Catch the ConstraintViolationException and then make sure that the violation is due to a duplicate (since there can be other reasons, like null fields).

The former has the disadvantage that you are checking for duplicates on every insert when the likelihood of there actually being a duplicate may be low. The latter will be faster for usual case where no duplicates occur, but has the disadvantage that you need to check for duplicates after the face. When a ConstraintViolationException is thrown it invalidates the current session; this means you will need to flush before doing a search of a duplicate.

Checking for duplicates before insert is probably the cleanest approach unless there is a major performance problem that you need to worry about. Make sure you do the lookup and insert in a transaction to ensure that someone doesn't add a duplicate between the lookup and insert, otherwise you will get a ConstraintViolationException.

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You can use @SqlInsert annotation on your entity, to change the sql hibernate uses to make insertion in Database, hibernate currently must be using this statement

insert into method(name, id) values (?,?)

If you are using mysql, you can use the @SqlInsert statement to change the insert sql by using insert ignore mysql statement

@SQLInsert(sql = "insert ignore into method(name, id) values (?,?)")

However you should get the insert sqls by enabling show sql mode in hibernate, since the order of the columns is generated via some logic, and their docs suggest this way.

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Just like Pascal said, Hibernate won't know if it is a duplicate until it has actually been insrted.

I encountered a similar situation before; several threads were doing insertions to the DB, but some of those would be duplicates. All I did was to catch and gracefully recover when one of those exceptions were thrown.

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Instead of using createQuery() in hibernate, use createSQLQuery() and try a query like "REPLACE INTO method (id) VALUES (123);"

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You can try catch the exception org.hibernate.exception.ConstraintViolationException and swallow the exception in your code

For example:

try {
    sessionFactory.getCurrentSession().saveOrUpdate(entity);
} catch (ConstraintViolationException e) {
    // Ignore the exception here by doing nothing
}

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This is how I solved this issue :

try {
     session.save(object);
    }catch(JDBCException exception) {
        Throwable cause = exception.getCause();
        if(cause!=null && cause.getMessage().contains("Duplicate entry")){
            session.clear(); 
            throw new DuplicateEntityException("Duplicate entry");
        }else{
            throw exception; 
        }
    }

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even if you catch the exception, there may be other problems

try{
       session.save(O);
       session.getTransaction().commit();
    }catch (HibernateException e) {
       System.out.println("you are carched ¤#%SD¤") ;
    }