Get physical column value with entity property value using hibernate

Question

I have a table T with columns defined as usual.

@Entity
@Table(name="T")
public class T {
@Column(name="test_id")
private Long testId;

}

Given entity property "testId", I want to get corresponding DB column name (i.e. "test_id"). How could it be achieved?

Edit 1: I want to keep this column at separate location with actual DB column name (test_id) than testId. I fetched these values from DB using HQL which have key as entity name (i.e. testId) and I want actual column name in DB.

Solution 1

If I understood your requirement correctly, you want to use HQL while having a consistent name for both DB column and the entity field, like this:

SELECT t.test_id FROM Test t 

instead of

SELECT t.testId FROM Test t 

There is only one way to do that - renaming the field to test_id. HQL works on entities, not on DB tables, so you must use proper field names in the query.

Since test_id contradicts the usual Java coding conventions, I would advise against it.

EDIT: Getting the annotation attribute value with reflection would work along this outline:

Field field = MyEntity.class.getDeclaredField("testId");
Column a = field.getAnnotation(Column.class);
String columnName = a.name();

Solution 2

I would try to avoid this by any means, but if you're really sure you'll need it, use:

Configuration configuration = sessionFactory.getConfiguration();
PersistentClass persistentClass = configuration
                .getClassMapping(T.class.getName());
String columnName = ((Column) persistentClass.getProperty("testId")
                .getColumnIterator().next()).getName();

See also Get table column names in Hibernate

Comments

[kostja]

could you please clarify your requirements? Do you want to rename the field in your code?

[instanceOfObject]

No, I don't want to rename. I just want to fetch db column_name corresponding to entity columnName.

[Adrian Shum]

Just curious: why would you want to do that?

[instanceOfObject]

I have got these logical values from HQL and want to store physical column name in the audit to keep track of the changes made on that column.

[jean]

It seems meaningless. Because you still have to provide a string which is the name of your field instead string of column name

[instanceOfObject]

I understand that HQL works on entities. What I want is to get DB column name from entity property (get test_id from testId). I have read that Hibernate Configurations could be used for this but not quite sure of the way.

[kostja]

So you want to extract the name attribute of the Column annotation, you could use reflection for that. Or am I misunderstanding you again?

[instanceOfObject]

Correct! Reflection is one way to do this :)