Changing annotation attribute value at runtime in java

Question

Some methods in our pojos model were annotated as follows:

@Column(name="cli_clipping_id", updatable=false, columnDefinition = "varchar(" + ModelUtils.ID_LENGTH + ") COLLATE utf8_bin") 

The columnDefinition attribute is dependent on the database provider, so if you try to reset the schema in HSQLDB using Hibernate, this will not work:

 [ERROR] 16 jun 12:58:42.480 PM main [org.hibernate.tool.hbm2ddl.SchemaExport] Unexpected token: COLLATE in statement [create table cms.edi_editorial_obj (edi_uuid varchar(23) COLLATE] 

To fix this, I think of this solution (but don't want to waste time if this is not possible) at runtime for each method column annotated:

• Get @Column annotation
• Create a copy of the column annotation by setting the columnDefinition null value using javaassist.
• set the column method annotation to the copy column annotation object that overrides the old one (I don't know what is possible)

Is it possible to “crack” these methods in this way?

Any help would be greatly appreciated ...

Answer 1

I do not think that the method you proposed is possible, because:

• The annotation value that you get at run time is actually a proxy class that implements the annotation interface. You cannot set new values ​​in your attributes.
• It is not possible to set new annotation values ​​for classes or methods at run time.

However, you can go to the xml configuration for Hibernate, where you can change the parameter outside the code.

Answer 2

If you build using ANT, you can take a precompilation step and use a regular expression to change the code in the files.

Answer 3

Although this is actually an old thread, the answer “Two questions above” is incorrect for point 2: In fact, cool annotations can be changed at runtime.

I'm still wondering how to do this for methods.