at times when u import the db it may erase ur userid and pwd. When the java tries to connect to the db it throws exception that this ip is not allowed to connect to the db; in such a case use the below fix. it removes the necessity to have userid and pwd to loginto the mysql
be careful that u dont do this on production dbs
This is generally the case when u try to import a database from a dump. The fix is to increase the max_allowed_packet size follow the below steps
This should do.
suppose we want to search for a string “abc” in a file then we use
grep “abc” /path/to/file/file.txt
but what if u want to search for either “abc” or “xyz”? u need to grep twice. instead use egrep
egrep “abc|xyz” /path/to/file/file.txt
the best use of egrep comes in when we tail a file and want to search for a set of strings in the tail eg:
tail –f /path/to/file/file.txt | egrep “abc|xyz”
getSession() –> the java doc says it will create a new session/ continue with the existing one based on getHibernateTemplate().setAllowCreate(…); set to true/ false.
How ever, i found the things to be diffarent. I had a 2 DAOs one executing: getHibernateTemplate().find(..); the other using getSession().createCriteria(..); They are wrapped by the same transaction interceptor. What i found is when the 2nd DAO runs the hibernate throws illegal state exception.
Why?? The getSession() always tries to crate a new session, if the setAllowCreate is set to false, then it throws illegal argument exception. Why this devaiation??? as always only god knows it.
To get the current session in 2nd DAO, i found the fix: getHibernateTemplate().getSessionFactory().getCurrentSession(); and things went off very fine.
Recently i had to do a query as:
select * from t_table where (t.a=’a’ and t.b=’b’) or (t.a=’aa’ and t.b=’bb’). One way to get over this is via HQL query… which i hate.. i wanted to do it using criterias… finally Conjunction and disjunctions came for resque. Below is the code.
Session session = getSession();
try {
Criteria crit = session.createCriteria(Table.class);
Disjunction conMerOrs = Restrictions.disjunction();
for (AB ab: ABList) {
Conjunction ands = new Conjunction();
ands.add(Restrictions.eq("a", ab.a()));
ands.add(Restrictions.eq("b", ab.b));
ors.add(ands);
}
crit = crit.add(ors);
return crit.list();
} finally {
session.close();
}
let me know if it helped
I hate using non-licensed tools. generally when it comes to code generation for Hibernate, pple tell of myeclipse; and heres the way to do it. Myeclipse usage requires licenses; so this is how pple get around it –uninstall it just before the trial expires and reinstall it again.
I hate all this crappy stuff and wanted a clean way to do it. I have used eclipse helios for this and guess it would work for other eclipse versions as well
Now the hibernate plugin is installed. Below i tell the steps to auto genrate the code
Now the qn: why did they build the plugin so complicated? why not have it a siimple one? all of it done in a wizard??? i donk know…
let me know if it helped you.
Below is the table def that caused the problem:
CREATE TABLE IF NOT EXISTS `T_ABC` (
`id` INT NOT NULL AUTO_INCREMENT ,
`source_col` int NOT NULL ,
PRIMARY KEY (`id`) ,
INDEX `fk_src_col` (`source_col` ASC) ,
CONSTRAINT `fk_src_col`
FOREIGN KEY (`source_col` )
REFERENCES `parent_table` (`id` )
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB;
and on execution it was giving the error ERROR 1005 (HY000): Can't create table schema.T_ABC.frm
The fix to issue is: that parent_table.id is of bigint type, while this table foreign key is only int; when i changed the source_col from int to big_int things went well.
hope this helps somebody.
So the problem stmt is as follows
Criteria criteria = getSession().createCriteria(CompositeKeyEntity.class);
criteria = criteria.add(Restrictions.in("id.subKey", list));
List<CompositeKey> list = criteria.list();
Let me know if it helps.
