public enum Category {

    A("TEST1"), B("TEST2"), C("TEST3");

    private String name;

    /**
     * @param name The human readable standard name
     */
    Category(final String name) {
        this.name = name;
    }

    /**
     * @return The human readable standard name
     */
    public String getName() {
        return name;
    }
}

@Entity
@Table(name = "TASK")
public class Task {

    @Id
    @Column(name = "id")
    private int id;

    @ElementCollection(targetClass = Category.class, fetch = FetchType.LAZY)
    @JoinTable(name = "TASK_CATEGORY", joinColumns = { @JoinColumn(name = "TASK_ID") })
    @Enumerated(EnumType.STRING)
    @Column(name = "CATEGORY", nullable = false)
    private final Set<Category> categories = new HashSet<>();

    public void addCategory(Category c) {
        categories.add(c);
    }

    public Set<Category> getCategories() {
        return categories;
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
             http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd"
    version="2.0">

    <persistence-unit name="HibernateTestPU">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>

        <class>hibernate.tests.entity.Task</class>
        <exclude-unlisted-classes>true</exclude-unlisted-classes>

        <properties>
            <property name="hibernate.connection.url" value="jdbc:h2:mem:hibernatetest" />
            <property name="hibernate.connection.driver_class" value="org.h2.Driver" />
            <property name="hibernate.connection.username" value="SA" />
            <property name="hibernate.connection.password" value="" />
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.format_sql" value="true" />
            <property name="hibernate.hbm2ddl.auto" value="update" />

            <property name="hibernate.order_inserts" value="true" />
        </properties>
    </persistence-unit>
</persistence>