Enterprise JavaBeans

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface Stateless {
    String name() default "";
    String mappedName() default "";
    String description() default "";
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface Stateful {
    String name() default "";
    String mappedName() default "";
    String description() default "";
    String passivationCapable() default "";
}

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface Singleton {
    String name() default "";
    String mappedName() default "";
    String description() default "";
}

public interface EJBContext {
    EJBHome getEJBHome() throws IllegalStateException;
    EJBLocalHome getEJBLocalHome() throws IllegalStateException;
    Properties getEnvironment();
    Identity getCallerIdentity();
    Principal getCallerPrincipal();
    boolean isCallerInRole(Identity role);
    boolean isCallerInRole(String roleName);
    UserTransaction getUserTransaction() throws IllegalStateException;
    void setRollbackOnly() throws IllegalStateException;
    boolean getRollbackOnly() throws IllegalStateException;
    TimerService getTimerService() throws IllegalStateException;
    Object lookup(String name) throws IllegalArgumentException;
    Map<String, Object> getContextData();
}

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface PostConstruct;

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface PreDestroy;

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface PostActivate;

@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface PrePassivate;

@Stateless
public class UserService {
    
    @PersistenceContext
    private EntityManager em;
    
    @PostConstruct
    public void init() {
        // Initialization logic
    }
    
    public User findUser(Long id) {
        return em.find(User.class, id);
    }
    
    @PreDestroy
    public void cleanup() {
        // Cleanup logic
    }
}