Q

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got from a JIRA post 

Auto generating hibernate code using Eclipse (not my eclipse)

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

1. in eclipse help > install new software > give the url: http://download.jboss.org/jbosstools/updates/stable/helios/ and hibernate - http://download.jboss.org/jbosstools/updates/development
2. say you added link 1, click on next and select all options then click on finish
3. then redo the above for the link 2 aswell.

Now the hibernate plugin is installed. Below i tell the steps to auto genrate the code

1. File > new > others > hibernate > new Hibgernate console configuration file
1. select the project name, configurae a new db connection, property file, configuration files (all will take abt 1 min to complete)
2. similarly do  File > new > others > hibernnate > new hingernate cfg.xml
3. similarly do FIle > new others > hibernate > new reverse engineering file
1. fill the step 1
2. the step2 click on refresh after having selected the console configuration file in the dropdown
3. select the table u r looking for
4. incase ur table has foreign keys select the paret table also
5. click on finish
4. Inthe top bar (where u see save, print icos) u should see a new RunAs icon ( in black suffix)
1. click on it you wil see a drop down
2. select hibernate code generation configurations
3. now double click on hiberante code generation (in the left tree)
4. in the right side select consolef configuration
5. select a temp directory, reverse engineering file we already created
6. and say run; Bingo.. the code generation is done.

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.

MySQL ERROR 1005 (HY000): Can't create table

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.

getHibernateTemplate().find() / query.list() returns list with null values

So the problem stmt is as follows

1. The Entity primary key is mapped as composite-id in hbm files. i.e.. all columns/ multiple columns of the entity is taken as composite key. This gnerally happens when u use code generatoros. 
2. now you say the below in criteria query

   Criteria criteria = getSession().createCriteria(CompositeKeyEntity.class);
   criteria = criteria.add(Restrictions.in("id.subKey", list));
   List<CompositeKey> list = criteria.list();

   
   
   
   
3. The above returns a list with entities are null.
   
   
   
   1. why? Tracing the src code figured out that hibernate checks each of the values of primary keys. and when ever he finds one of the value as null doesn’t return the object. (org.hibernate.type.ComponentType.hydrate())
      
   2. This is logical as we shouldn’t have nulls in primary keys. But the problem is its not documented anywhere!
   
   
4. so the fix: make all composite key columns as not-null; and give a default to each of the column.

 

Let me know if it helps.

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