✅ What is a Hibernate mapping file?
Answer:
A Hibernate mapping file is an XML file (usually ending with .hbm.xml) that tells Hibernate how to map a Java class to a database table, and how the class’s fields map to table columns.
🔹 What it does:
- Defines the mapping between your entity’s properties and the database schema.
- Specifies primary keys, column names, data types, and relationships (one-to-one, one-to-many, etc.).
- Lets you customize mappings without modifying Java code (especially useful before JPA annotations became common).
🔹 Example Hibernate mapping file (User.hbm.xml):
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.example.User" table="users">
<id name="id" column="id">
<generator class="native"/>
</id>
<property name="username" column="username"/>
<property name="email" column="email"/>
</class>
</hibernate-mapping>
✅ This tells Hibernate to map com.example.User to the users table, map id as the primary key, and map username and email fields to their respective columns.
🔹 How it’s used:
- You register mapping files in
hibernate.cfg.xml:
<mapping resource="com/example/User.hbm.xml"/>
Or add them programmatically:
config.addResource("com/example/User.hbm.xml");
🔹 Modern alternative:
- JPA annotations (
@Entity,@Table,@Column, etc.) are now the standard way to define mappings directly in Java code, making mapping files optional in most modern apps.
✅ Key takeaway:
A Hibernate mapping file defines the bridge between your object model and relational database schema using XML — but today, most developers prefer annotations for clarity and maintainability.