Automatic Database Schema Generation

• Automatically generate DDL at application startup
• Table-centric -> Object-centric
• Generate appropriate DDL for the database using database dialects
• The DDL generated this way is only used on development machines
• The generated DDL should not be used on production servers, or should be used after appropriate refinement

Properties #

• create: Deletes existing tables and recreates them (DROP + CREATE)
• create-drop: Same as create, but drops tables on exit
• update: Applies only changes (not for use in production DBs)
• validate: Only checks if entities and tables are mapped correctly
• none: Not used

Caution #

• Never use create, create-drop, or update on production machines.
• For initial development stages, use create or update
• For test servers, use update or validate
• For staging and production, use validate or none

DDL Generation Features #

• Add constraints
• @Column(nullable = false, legnth = 10)
• Add unique constraints
• @Table(uniqueConstraints = {@UniqueConstraint( name = "NAME_AGE_UNIQUE" , columnNames = {"NAME", "AGE"}) })
• The DDL generation feature is only used for automatic DDL generation and does not affect JPA's execution logic (database impact).