IT Education Guidance - Hibernate: Hibernate ( XML mapping )

Hibernate ( XML mapping ) - 1st Program

First Hibernate Program - XML mapping

This lesson shows the basic steps of creating a simple hibernate application by using eclipse IDE.

Step 1 - Setup the development environment for Hibernate

Step 2 - Setup the database

Step 3 - Create POJO class ( Employee.java )

Step 4 - Create respective mapping file ( hbm.xml )

Step 5 - Hibernate Configurations ( hibernate.cfg.xml )

Step 6 - Create Helper class ( HibernateUtil.java )

Step 7 - Create class to do the execution ( ExecuteEmployee.java )

Step 1 - Setup the development environment for Hibernate

To set up the development environment you need to carry out below operations.

(Assume you already install Java to your development environment and as well as you familiar with the eclipse IDE.)

Step 1.1 - Create new a Java project “BasicHibernateApplication”

Step 1.2 - Add JDBC Driver for MySQL

For this application used MySQL as the database application. Therefore need to add the “mysql- connector-java-5.1.18-bin.jar” JDBC driver jar.

Create a new folder (ex: “DriverLib”) under your project and copy above file into that folder. Once you copied it, then you need to configure it on the build path. For that use below steps.

i) Right click the project

ii) Select Build Path

iii) Configure Build Path

iv) Go to Libraries tab and browse and add the jar file.

Step 1.3 - Add Hibernate Prerequisites

Following is the list of packages/libraries required to develop hibernate application.

For use annotation, it uses

* ejb3-persistence.jar

* hibernate-annotations.jar

* hibernate-commons-annotations.jar

Create a new lib folder under your project and copy above files into the lib folder. Once you copy the files

then you need to configure the build path. For that use below steps.

i) Right click the project

ii) Select Build Path

iii) Configure Build Path

iv) Go to Libraries tab and browse and add all jar files

Step 2 - Setup the database

For this example I use MySQL database and my database name is “myworkspace” and create a table employee. The primary key is empid.

Step 3 - Create POJO class

Create a POJO (Plain Old Java Object) class that represents the employee. This is a simple class which has property getter and setter methods and private visibility for the fields.

Step 4 - Create respective mapping file

Hibernate mappings which used to know how to load and store objects of the persistent class.
The mapping file tells Hibernate what is the table and what are the columns in that table in order to carry on the operations.

Create a mapping file “employee.hbm.xml” which maps “Employee.java” POJO and the “employee” table in the database.

Step 5 - Hibernate Configurations

Next step is configure Hibernate. This shows hibernate how to obtain and manage the connections with the database.

To create the configuration file, right click on the “src" folder and select New --> File. Now specify the configuration file name as hibernate.cfg.xml and save it.

hibernate.connection.url – Give the database connection url.

hibernate.connection.username – Give the database user name.

hibernate.connection.password – Give the database password if exists.

hibernate.connection.driver_class – Give the appropriate driver class according to the database which is using your application.

<mapping resource="hbm/employee.hbm.xml"/> - This is the mapping hbm file.

Step 6 - Create Helper class

Startup Hibernate by creating a thread-safe, global org.hibernate.SessionFactory object and this object is instantiated once. A org.hibernate.SessionFactory is used to obtain an instance of org.hibernate.Session this represents a single-threaded unit of work.

Create a HibernateUtil helper class that takes care of startup and makes accessing the org.hibernate.SessionFactory more convenient.