JPA2 includes the new metamodel, which allows us to use JPA typesafe. To see what has changed since JPA 1, I can recommend this and this blog.

Generating the metamodel turned out to be somewhat harder than I first thought. Since I’m a JBoss alcoholic, I’m using Hibernate as persistence provider with and the jpamodelgen subproject.

Generating the metamodel

According to the official documentation, all we need to do is add the hibernate-jpamodelgen to the classpath.

<dependency>
    <groupId>org.hibernate</groupId>
    <artifactId>hibernate-jpamodelgen</artifactId>
</dependency>

However, this resulted  in nothing. The only thing that did work for me was adding extra configuration with maven-annotation-plugin.

<plugin>
    <groupId>org.bsc.maven</groupId>
    <artifactId>maven-processor-plugin</artifactId>
    <executions>
        <execution>
            <id>process</id>
            <goals>
                <goal>process</goal>
            </goals>
            <phase>generate-sources</phase>
            <configuration>
                <!-- source output directory -->
                <outputDirectory>
target/metamodel
</outputDirectory>
            </configuration>
        </execution>
    </executions>
</plugin>
<plugin>
    <groupId>org.codehaus.mojo</groupId>
    <artifactId>build-helper-maven-plugin</artifactId>
    <version>1.3</version>
    <executions>
        <execution>
            <id>add-source</id>
            <phase>generate-sources</phase>
            <goals>
                <goal>add-source</goal>
            </goals>
            <configuration>
                <sources>
                    <source>target/metamodel</source>
                </sources>
            </configuration>
        </execution>
    </executions>
</plugin>

Success! The User.java file

@Entity
public class User implements UserDetails {
 /** The Constant serialVersionUID. */
 private static final long serialVersionUID = 1L;
 /** The user name. */
 @Id
 @Column(name = "USER_ID")
 @Size(min = 3, max = 10)
 private String username;
 /** The password. */
 @NotNull
 @Size(min = 6, max = 40)
 @Column(name = "PASSWORD")
 private String password;
 /** The name. */
 @Column(name = "NAME")
 private String name;
 /** The first name. */
 @Column(name = "FIRSTNAME")
 private String firstName;

was transformed into User_.java

import javax.persistence.metamodel.SingularAttribute;
import javax.persistence.metamodel.StaticMetamodel;
@StaticMetamodel(User.class)
public abstract class User_ {
 public static volatile SingularAttribute<User, String> username;
 public static volatile SingularAttribute<User, String> name;
 public static volatile SingularAttribute<User, String> firstName;
 public static volatile SingularAttribute<User, String> password;
}

Now we can use the model to do typysafe queries:

public UserDetails loadUserByUsername(final String username) throws UsernameNotFoundException,
 DataAccessException {
 CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
 CriteriaQuery<User> criteriaQuery = criteriaBuilder.createQuery(User.class);
 Root<User> u = criteriaQuery.from(User.class);
 Predicate usernameCondition = criteriaBuilder.equal(u.get(User_.username), username);
 criteriaQuery.where(usernameCondition);
 TypedQuery<User> query = entityManager.createQuery(criteriaQuery);
 try {
 return (User) query.getSingleResult();
 } catch (NoResultException e) {
 throw new UsernameNotFoundException("User not found: " + username, e);
 }
 }

The program for our upcoming event is complete! Here it is…

18:00 – 19:00: Kabir Khan - What’s Cooking in JBoss AS 6

Kabir will talk about the JBoss AS 6 roadmap, the new development model, ongoing optimizations since AS 6. He will also give a bird’s eye overview of the new projects that will be bundled in AS 6, such as Weld, HornetQ, RestEasy and several more. There will be a short demo at the end showing some of the new features in AS.

19:00 – 20:00: Kris Verlaenen – Looking forward to the future of (j)BPM

There’s much going on in the area of BPM. This presentation will offer you an overview of how the jBPM project will continue to offer you business processes support (in their entire life cycle), while also taking these new challenges into account, like more dynamic or adaptive processes, standardization using the BPMN2 process definition language, etc.

I think we can all agree on the fact that these talks will be very interesting (to say the least).
So… do not forget to register for this event! (Maximium capacity is set to 45 people)

See you soon on the 3rd of June at Xplore premises!