Implementação dinâmica de DAO

package org.superbiz.dynamic;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.Id;
import jakarta.persistence.NamedQueries;
import jakarta.persistence.NamedQuery;

@Entity
@NamedQueries({
        @NamedQuery(name = "dynamic-ejb-impl-test.query", query = "SELECT u FROM User AS u WHERE u.name LIKE :name"),
        @NamedQuery(name = "dynamic-ejb-impl-test.all", query = "SELECT u FROM User AS u")
})
public class User {
    @Id
    @GeneratedValue
    private long id;
    private String name;
    private int age;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

package org.superbiz.dynamic;


import jakarta.ejb.Stateless;
import jakarta.persistence.PersistenceContext;
import java.util.Collection;
import java.util.Map;

@Stateless
@PersistenceContext(name = "dynamic")
public interface UserDao {
    User findById(long id);

    Collection<User> findByName(String name);

    Collection<User> findByNameAndAge(String name, int age);

    Collection<User> findAll();

    Collection<User> findAll(int first, int max);

    Collection<User> namedQuery(String name, Map<String, ?> params, int first, int max);

    Collection<User> namedQuery(String name, int first, int max, Map<String, ?> params);

    Collection<User> namedQuery(String name, Map<String, ?> params);

    Collection<User> namedQuery(String name);

    Collection<User> query(String value, Map<String, ?> params);

    void save(User u);

    void delete(User u);

    User update(User u);
}

<persistence version="2.0"
             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">
  <persistence-unit name="dynamic" transaction-type="JTA">
    <jta-data-source>jdbc/dynamicDB</jta-data-source>
    <class>org.superbiz.dynamic.User</class>
    <properties>
      <property name="openjpa.jdbc.SynchronizeMappings" value="buildSchema(ForeignKeys=true)"/>
    </properties>
  </persistence-unit>
</persistence>

package org.superbiz.dynamic;

import junit.framework.Assert;
import org.junit.BeforeClass;
import org.junit.Test;

import jakarta.ejb.EJBException;
import jakarta.ejb.Stateless;
import jakarta.ejb.embeddable.EJBContainer;
import javax.naming.Context;
import jakarta.persistence.EntityManager;
import jakarta.persistence.NoResultException;
import jakarta.persistence.PersistenceContext;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertNotNull;
import static junit.framework.Assert.assertTrue;

public class DynamicUserDaoTest {
    private static UserDao dao;
    private static Util util;

    @BeforeClass
    public static void init() throws Exception {
        final Properties p = new Properties();
        p.put("jdbc/dynamicDB", "new://Resource?type=DataSource");
        p.put("jdbc/dynamicDB.JdbcDriver", "org.hsqldb.jdbcDriver");
        p.put("jdbc/dynamicDB.JdbcUrl", "jdbc:hsqldb:mem:moviedb");
        p.put("jdbc/dynamicDB.UserName", "sa");
        p.put("jdbc/dynamicDB.Password", "");

        final Context context = EJBContainer.createEJBContainer(p).getContext();
        dao = (UserDao) context.lookup("java:global/dynamic-dao-implementation/UserDao");
        util = (Util) context.lookup("java:global/dynamic-dao-implementation/Util");

        util.init(); // init database
    }

    @Test
    public void simple() {
        User user = dao.findById(1);
        assertNotNull(user);
        assertEquals(1, user.getId());
    }

    @Test
    public void findAll() {
        Collection<User> users = dao.findAll();
        assertEquals(10, users.size());
    }

    @Test
    public void pagination() {
        Collection<User> users = dao.findAll(0, 5);
        assertEquals(5, users.size());

        users = dao.findAll(6, 1);
        assertEquals(1, users.size());
        assertEquals(7, users.iterator().next().getId());
    }

    @Test
    public void persist() {
        User u = new User();
        dao.save(u);
        assertNotNull(u.getId());
        util.remove(u);
    }

    @Test
    public void remove() {
        User u = new User();
        dao.save(u);
        assertNotNull(u.getId());
        dao.delete(u);
        try {
            dao.findById(u.getId());
            Assert.fail();
        } catch (EJBException ee) {
            assertTrue(ee.getCause() instanceof NoResultException);
        }
    }

    @Test
    public void merge() {
        User u = new User();
        u.setAge(1);
        dao.save(u);
        assertEquals(1, u.getAge());
        assertNotNull(u.getId());

        u.setAge(2);
        dao.update(u);
        assertEquals(2, u.getAge());

        dao.delete(u);
    }

    @Test
    public void oneCriteria() {
        Collection<User> users = dao.findByName("foo");
        assertEquals(4, users.size());
        for (User user : users) {
            assertEquals("foo", user.getName());
        }
    }

    @Test
    public void twoCriteria() {
        Collection<User> users = dao.findByNameAndAge("bar-1", 1);
        assertEquals(1, users.size());

        User user = users.iterator().next();
        assertEquals("bar-1", user.getName());
        assertEquals(1, user.getAge());
    }

    @Test
    public void query() {
        Map<String, Object> params = new HashMap<String, Object>();
        params.put("name", "foo");

        Collection<User> users = dao.namedQuery("dynamic-ejb-impl-test.query", params, 0, 100);
        assertEquals(4, users.size());

        users = dao.namedQuery("dynamic-ejb-impl-test.query", params);
        assertEquals(4, users.size());

        users = dao.namedQuery("dynamic-ejb-impl-test.query", params, 0, 2);
        assertEquals(2, users.size());

        users = dao.namedQuery("dynamic-ejb-impl-test.query", 0, 2, params);
        assertEquals(2, users.size());

        users = dao.namedQuery("dynamic-ejb-impl-test.all");
        assertEquals(10, users.size());

        params.remove("name");
        params.put("age", 1);
        users = dao.query("SELECT u FROM User AS u WHERE u.age = :age", params);
        assertEquals(3, users.size());
    }

    @Stateless
    public static class Util {
        @PersistenceContext
        private EntityManager em;

        public void remove(User o) {
            em.remove(em.find(User.class, o.getId()));
        }

        public void init() {
            for (int i = 0; i < 10; i++) {
                User u = new User();
                u.setAge(i % 4);
                if (i % 3 == 0) {
                    u.setName("foo");
                } else {
                    u.setName("bar-" + i);
                }
                em.persist(u);
            }
        }
    }
}