CHAPTER 8 Legacy databases and custom SQL operation:
CHAPTER 8 Legacy databases and custom SQL operation: in this case, the greater-than comparison with the ranking property, which is also numeric. If your function returns a resultset cursor, as in previous sections, you can even map it as a named query and let Hibernate marshal the resultset into an object graph. Finally, remember that stored procedures and functions, especially in legacy databases, sometimes can t be mapped in Hibernate; in such cases you have to fall back to plain JDBC. Sometimes you can wrap a legacy stored procedure with another stored procedure that has the parameter interface expected by Hibernate. There are too many varieties and special cases to be covered in a generic mapping tool. However, future versions of Hibernate will improve mapping capabilities we expect better handling of parameters (no more counting of question marks) and support for arbitrary input and output arguments to be available in the near future. You ve now completed customization of runtime SQL queries and DML. Let s switch perspective and customize the SQL used for the creation and modification of the database schema, the DDL. 8.3 Improving schema DDL Customizing the DDL in your Hibernate application is something you ll usually consider only when you generate the database schema with Hibernate s toolset. If a schema already exists, such customizations won t affect the runtime behavior of Hibernate. You can export DDL to a text file or execute it directly on your database whenever you run your integration tests. Because DDL is mostly vendor-specific, every option you put in your mapping metadata has the potential to bind the metadata to a particular database product keep this in mind when applying the following features. We separate DDL customization into two categories: Naming automatically generated database objects, such as tables, columns, and constraints explicitly in mapping metadata, instead of relying on the automatic naming derived from the Java class and property names by Hibernate. We already discussed the built-in mechanism and options for quoting and extending names in chapter 4, section 4.3.5, Quoting SQL identifiers. We next look at other options you can enable to beautify your generated DDL scripts.
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