Using EJB and JPA for data caching

Knowing how to build a simple and local cache for your application is an important skill. It may have a big impact on some data access performance and it is quite easy to do.

This recipe will show you how.

Getting ready

Simply add a Java EE dependency to your project:

        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-web-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>

How to do it...

1. Let's create a User class to be our cached object:

public class User {

    private String name;
    private String email;

    //DO NOT FORGET TO IMPLEMENT THE GETTERS AND SETTERS
}

2. And then create a singleton to hold our user list cache:

@Singleton
@Startup
public class UserCacheBean {

    protected Queue<User> cache = null;

    @PersistenceContext
    private EntityManager em;

    public UserCacheBean() {
    }
...