Hibernate Configuration (original) (raw)

Hibernate requires to know in advance where to find the mapping information that defines how your Java classes relate to the database tables. Hibernate also requires a set of configuration settings related to database and other related parameters. All such information is usually supplied as a standard Java properties file called hibernate.properties, or as an XML file named hibernate.cfg.xml.

I will consider XML formatted file hibernate.cfg.xml to specify required Hibernate properties in my examples. Most of the properties take their default values and it is not required to specify them in the property file unless it is really required. This file is kept in the root directory of your application's classpath.

Hibernate Properties

Following is the list of important properties, you will be required to configure for a databases in a standalone situation −

If you are using a database along with an application server and JNDI, then you would have to configure the following properties −

Hibernate with MySQL Database

MySQL is one of the most popular open-source database systems available today. Let us create hibernate.cfg.xml configuration file and place it in the root of your application's classpath. You will have to make sure that you have testdb database available in your MySQL database and you have a user test available to access the database.

The XML configuration file must conform to the Hibernate 3 Configuration DTD, which is available at http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd.

The above configuration file includes tags, which are related to hibernatemapping file and we will see in next chapter what exactly a hibernate mapping file is and how and why do we use it?

hbm2ddl.auto Property

The hbm2ddl.auto property in Hibernate defines how your database schema is handled. Possible values are:

• create − If the value is 'create', Hibernate creates a new table in the database when the SessionFactory object is created. In case a table exists in the database with the same name, it deletes the table along with data and creates a new table.
• update − If the value is 'update', then Hibernate first validates whether the table is present in the database. If present, it alters that table as per the changes. If not, it creates a new one.
• validate − If the value is 'validate', then Hibernate only verifies whether the table is present. If the table does not exist then it throws an exception.
• create-drop − If the value is 'create-drop', then Hibernate creates a new table when SessionFactory is created, performs required operations, and deletes the table when SessionFactory is destroyed. This value is used for testing hibernate code.
• none − It does not make any changes to the schema.

Hibernate Dialect

A database dialect is a configuration option that allows software to translate general SQL statements into vendor-specific DDL and DML. Different database products, such as PostgreSQL, MySQL, Oracle, and SQL Server, have their own variant of SQL, which are called SQL dialects.

Following is the list of various important databases dialect property type −