Working example of EclipseLink static weaving

eclipselink-entity

This project contains three simple entity classes. Dept has many Employee, and Employee has one Phone.

Dept

@Entity
public class Dept implements Serializable {
    @Id
    private Long id;
    private String deptName;
    @OneToMany(mappedBy = "dept")
    private List<Employee> employees;

    // accessors omitted

Employee

@Entity
public class Employee implements Serializable {
    @Id
    private Long id;
    @ManyToOne(fetch = FetchType.EAGER) // default
    @JoinColumn(nullable = false)
    private Dept dept;
    private String firstName;
    private String lastName;
    @OneToOne(mappedBy = "employee", fetch = FetchType.LAZY) // overridden by LAZY
    private Phone phone;

    // accessors omitted

Note that the relation Employee.dept is set to EAGER, and Employee.phone is set to LAZY as FetchType.

Phone

@Entity
public class Phone implements Serializable {
    @Id
    @OneToOne
    @JoinColumn(nullable = false)
    private Employee employee;
    private String phoneNumber;

    // accessors omitted

persistence.xml

The persistence descriptor requires a property called eclipselink.weaving with the value static to enable static weaving.

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="myPU" transaction-type="RESOURCE_LOCAL">
        <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
        <exclude-unlisted-classes>false</exclude-unlisted-classes>
        <shared-cache-mode>NONE</shared-cache-mode>
        <properties>
            <property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/>
            <property name="javax.persistence.jdbc.url" value="jdbc:derby:memory:myDB;create=true"/>
            <property name="javax.persistence.jdbc.user" value="app"/>
            <property name="javax.persistence.jdbc.password" value="app"/>
            <property name="javax.persistence.schema-generation.database.action" value="drop-and-create"/>
            <property name="eclipselink.weaving" value="static"/>
            <property name="eclipselink.logging.level" value="FINE"/>
            <property name="eclipselink.logging.parameters" value="true"/>
        </properties>
    </persistence-unit>
</persistence>

pom.xml

The static weaving will be done by a convenient Maven plugin. Just put following plugin definition in your pom.xml and execute mvn clean install.

<build>
    <plugins>
        <plugin>
            <groupId>de.empulse.eclipselink</groupId>
            <artifactId>staticweave-maven-plugin</artifactId>
            <version>1.0.0</version>
            <executions>
                <execution>
                    <phase>process-classes</phase>
                    <goals>
                        <goal>weave</goal>
                    </goals>
                    <configuration>
                        <persistenceXMLLocation>META-INF/persistence.xml</persistenceXMLLocation>
                        <logLevel>FINE</logLevel>
                    </configuration>
                </execution>
            </executions>
            <dependencies>
                <dependency>
                    <groupId>org.eclipse.persistence</groupId>
                    <artifactId>org.eclipse.persistence.jpa</artifactId>
                    <version>${eclipselink.version}</version>
                </dependency>
            </dependencies>
        </plugin>
    </plugins>
</build>

eclipselink-example

This project is a client of the preceding eclipselink-entity project. It has a Main class which simply populates some records then fetches them.

public class Main {
    public static void main(String[] args) {
        EntityManagerFactory emf = null;
        try {
            emf = Persistence.createEntityManagerFactory("myPU");
            EntityManager em = null;

            // Populating data
            try {
                em = emf.createEntityManager();
                final EntityTransaction tx = em.getTransaction();
                tx.begin();

                Dept dept = new Dept();
                dept.setId(1l);
                dept.setDeptName("Engineering");
                dept.setEmployees(new ArrayList<>());
                em.persist(dept);

                Employee emp = new Employee();
                emp.setId(1l);
                emp.setFirstName("Jane");
                emp.setLastName("Doe");
                dept.getEmployees().add(emp);
                emp.setDept(dept);
                em.persist(emp);

                Phone phone = new Phone();
                phone.setPhoneNumber("000-1111-2222");
                phone.setEmployee(emp);
                emp.setPhone(phone);
                em.persist(phone);

                tx.commit();
            } finally { if (em != null) { em.close(); } }

            System.out.println("<<< Populating done >>>");

            try {
                em = emf.createEntityManager();
                final Employee emp = em.find(Employee.class, 1l);

                System.out.println(emp.getFirstName() + " " + emp.getLastName());

                // EAGER
                System.out.println(emp.getDept().getDeptName());
                // LAZY
                System.out.println(emp.getPhone().getPhoneNumber());
            } finally { if (em != null) { em.close(); } }
        } finally { if (emf != null) { emf.close(); } }
    }
}

Here you can see the Phone entity has lazily fetched while Dept entity was eagerly fetched:

<<< Populating done >>>
[EL Fine]: sql: 2015-10-24 03:18:23.389--ServerSession(1216590855)--Connection(1488298739)--Thread(Thread[main,5,main])--SELECT ID, FIRSTNAME, LASTNAME, DEPT_ID FROM EMPLOYEE WHERE (ID = ?)
	bind => [1]
[EL Fine]: sql: 2015-10-24 03:18:23.408--ServerSession(1216590855)--Connection(1488298739)--Thread(Thread[main,5,main])--SELECT ID, DEPTNAME FROM DEPT WHERE (ID = ?)
	bind => [1]
Jane Doe
Engineering
[EL Fine]: sql: 2015-10-24 03:18:23.413--ServerSession(1216590855)--Connection(1488298739)--Thread(Thread[main,5,main])--SELECT PHONENUMBER, EMPLOYEE_ID FROM PHONE WHERE (EMPLOYEE_ID = ?)
	bind => [1]
000-1111-2222

This example uses in-memory Apache Derby so you don’t need to set up any databases to execute this example. complete projects can be obtained from following GitHub repositories:

Also here’s build.gradle example: https://github.com/lbtc-xxx/eclipselink-entity/blob/master/build.gradle

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