Using ''Hibernate Tools'' with Eclipse

Hibernate is perhaps the most widely accepted framework for ORM (Object Relational Mapping) and object persistence. However you would always prefer a wizard based tool for common tasks such as creating configuration files, generating or editing mappings, or even reverse engineering your applications' domain classes from hibernate mappings.

In this article, we'll configure 'Hibernate Tools' and see how to reverse engineer your POJOs (Plain Old Java Objects) using this plug-in for Eclipse. You can download and install the latest version of this (3.2 Beta 2 at the time of writing this piece) from www.hibernate.org/30.html. We took a MySQL database for our exercise. If you use some other database, then you'll have to use different configuration properties.

Generate Configuration file
Once installed, you need to first switch to the Hibernate perspective (in your Eclipse IDE) from Window>Open Perspective>Hibernate Console. From here, launch the 'Create Hibernate Configuration' wizard as New>Hibernate Configuration File. Choose a location for the file in your application directory and proceed.

In the next page you need to provide Database Dialect (MySQL in our case), the driver class (org.gjt.mm.mysql. Driver or com.jdbc.mysql.Driver), the database username and password. Other fields such as Default Schema, Default Catalog, can be left empty (optional). Also check the option for 'Create Console Configuration' and click on Finish to generate the .cfg.xml configuration file.

Console configuration
Create the Console configuration by New>Hibernate Console Configuration option. In the wizard you need to provide values for a name of the console, and also add the JAR file that represents the connector you are using for your application. In our case this was the mysql-connector-java-bin-3.1.12-bin.jar. Click on Finish to complete the task. You can then view your database in the 'Hibernate Configurations' tab of the Project Explorer window.

Reverse Engineering classes
To create POJOs, go to Run>Hibernate Code Generation. Then populate a value for the o/p directory and provide an optional package name. The Exporters tab specifies the type of code that should be generated. Each selection represents an 'Exporter,' responsible for generating the code. Check the option for 'Use Java 5 syntax' and click on 'Run.' The classes will be generated in the specified output directory.

Exporters tab
The Exporters tab contains seven options categorized in two groups. The first group contains two options-Use Java 5 syntax and EJB 3 Annotations. As the name suggests, the first option creates POJOs using JDK 1.5 syntax constructs only, while the second option creates classes with EJB 3 syntax using annotations.

The second group has five options: Domain Code (.java) that creates POJOs for all the persistent entities and components; Hibernate XML Mappings that generates Hibernate mappings for each entity in the database; DAO code (.java) option that creates a set of DAO for the entities; Hibernate XML Configuration generates hibernate.cfg. xml file that keeps Mappings updated; Schema Definition (.html) that generates HTML docs which document the database schema; and JBoss Seam Skeleton App (misc) that creates the Seam skeleton app including annotated POJOs, Seam controller Beans, a JSP Presentation layer, and a Build.xml file. Since the option generates the entire application, you should configure the root dir of your project as the target output dir.

Source: PCQuest