> I'm implementing a feature of my project that visually show the relations
> between tables in database.Therefore I want to know the effective way to
> get all the constrains exist in database (e.g Primary key constrain,
> foreign key contrain,...).I have try to see all system tables but it's
> really a mess.Isthere any way?

Please check the JDBC documentation for the following methods:

DatabaseMetaData.getExportedKeys(String, String, String)
DatabaseMetaData.getImportedKeys(String, String, String)

Roman