amber (jpa) tutorials

Amber's persistence based on JPA (the Java Persistence Architecture) supports a field-based relational model: each Java field represents a database column. The tutorial shows the configuration, classes, and client code for a single-table entity.

Basic persistence example showing configuration, classes, and client code for a single-table bean.

This example focuses on:

• Introduces persistence fundamental concepts
• Setting up the database
• Developing the Entity classes
• Developing a Servlet to lookup and use the entity bean
• Configuring Resin to deploy the bean and use JNDI

The Amber Query API resembles the JDBC PreparedStatement with enhanced SQL and direct support for objects.

The Many-to-One link is the foundation of persistent relations. It links a source table to a destination with a database REFERENCES column. Many-to-One adds two capabilities: SQL extensions for links and direct lookup of target beans through field references.

The @OneToMany relation adds collection extensions to the query language and provides a Java Collection containing the children. @OneToMany represents a collection of children belonging to a parent, like students in Gryffindor house at Hogwarts school.

The Many-To-One tutorial illustrated that a many-to-one relation links one source entity to another target entity. A one-to-many relation links the target entity back to the source entity.

In this example, each House has many Students, each Student has one House. House has a one-to-many relationship with Student, Student has a many-to-one relationship with House

Illustrates using many-to-many relations of EJB 3.0.

Amber supports database-backed inheritance, allowing for persistent-backed polymorphism and more sophisticated object-oriented modelling.

The example uses a single table to represent both Student and Prefect values. The "type" column serves as a discriminator to select the proper type.

HttpSessions combined with Amber improve the flexibility and performance of persistent sessions.