Hur man replikerar INSERT/UPDATE/DELETE-satser med JPA och Hibernate

Databastabeller

Förutsatt att du har följande två tabeller:

CREATE TABLE old_post (
    id int8 NOT NULL,
    title varchar(255),
    version int4 NOT NULL,
    PRIMARY KEY (id)
)
                                                  
CREATE TABLE post (
    id int8 NOT NULL,
    created_on date, 
    title varchar(255),
    version int4 NOT NULL,
    PRIMARY KEY (id)
)

JPA-enhet

old_post tabellen måste replikeras med den nyare post . Lägg märke till att post tabellen har fler kolumner nu än den gamla tabellen.

Vi behöver bara mappa Post enhet:

@Entity(name = "Post")
@Table(name = "post")
public static class Post {

    @Id
    private Long id;

    private String title;

    @Column(name = "created_on")
    private LocalDate createdOn = LocalDate.now();

    @Version
    private int version;

    //Getters and setters omitted for brevity
}

Vilolägesavlyssnare

Nu måste vi registrera 3 händelseavlyssnare för att fånga upp operationerna INSERT, UPDATE och DELETE för Post enhet.

Vi kan göra detta via följande evenemangslyssnare:

public class ReplicationInsertEventListener 
        implements PostInsertEventListener {
 
    public static final ReplicationInsertEventListener INSTANCE = 
        new ReplicationInsertEventListener();
 
    @Override
    public void onPostInsert(
            PostInsertEvent event) 
            throws HibernateException {
        final Object entity = event.getEntity();
 
        if(entity instanceof Post) {
            Post post = (Post) entity;
 
            event.getSession().createNativeQuery(
                "INSERT INTO old_post (id, title, version) " +
                "VALUES (:id, :title, :version)")
            .setParameter("id", post.getId())
            .setParameter("title", post.getTitle())
            .setParameter("version", post.getVersion())
            .setFlushMode(FlushMode.MANUAL)
            .executeUpdate();
        }
    }
 
    @Override
    public boolean requiresPostCommitHanding(
            EntityPersister persister) {
        return false;
    }
}

public class ReplicationUpdateEventListener 
    implements PostUpdateEventListener {

    public static final ReplicationUpdateEventListener INSTANCE = 
        new ReplicationUpdateEventListener();

    @Override
    public void onPostUpdate(
            PostUpdateEvent event) {
        final Object entity = event.getEntity();

        if(entity instanceof Post) {
            Post post = (Post) entity;

            event.getSession().createNativeQuery(
                "UPDATE old_post " +
                "SET title = :title, version = :version " +
                "WHERE id = :id")
            .setParameter("id", post.getId())
            .setParameter("title", post.getTitle())
            .setParameter("version", post.getVersion())
            .setFlushMode(FlushMode.MANUAL)
            .executeUpdate();
        }
    }

    @Override
    public boolean requiresPostCommitHanding(
            EntityPersister persister) {
        return false;
    }
}

public class ReplicationDeleteEventListener 
        implements PreDeleteEventListener {

    public static final ReplicationDeleteEventListener INSTANCE = 
        new ReplicationDeleteEventListener();

    @Override
    public boolean onPreDelete(
            PreDeleteEvent event) {
        final Object entity = event.getEntity();

        if(entity instanceof Post) {
            Post post = (Post) entity;

            event.getSession().createNativeQuery(
                "DELETE FROM old_post " +
                "WHERE id = :id")
            .setParameter("id", post.getId())
            .setFlushMode(FlushMode.MANUAL)
            .executeUpdate();
        }

        return false;
    }
}

De 3 händelseavlyssnarna kan registreras med en Hibernate Integrator :

public class ReplicationEventListenerIntegrator 
        implements Integrator {

    public static final ReplicationEventListenerIntegrator INSTANCE = 
        new ReplicationEventListenerIntegrator();

    @Override
    public void integrate(
            Metadata metadata,
            SessionFactoryImplementor sessionFactory,
            SessionFactoryServiceRegistry serviceRegistry) {

        final EventListenerRegistry eventListenerRegistry =
                serviceRegistry.getService(EventListenerRegistry.class);

        eventListenerRegistry.appendListeners(
            EventType.POST_INSERT, 
            ReplicationInsertEventListener.INSTANCE
        );

        eventListenerRegistry.appendListeners(
            EventType.POST_UPDATE, 
            ReplicationUpdateEventListener.INSTANCE
        );

        eventListenerRegistry.appendListeners(
            EventType.PRE_DELETE, 
            ReplicationDeleteEventListener.INSTANCE
        );
    }

    @Override
    public void disintegrate(
            SessionFactoryImplementor sessionFactory,
            SessionFactoryServiceRegistry serviceRegistry) {

    }
}

Och för att instruera Hibernate att använda denna anpassade Integrator måste du ställa in hibernate.integrator_provider konfigurationsegenskap:

<property name="hibernate.integrator_provider"
          value="com.vladmihalcea.book.hpjp.hibernate.listener.ReplicationEventListenerIntegrator "/>

Testtid

Nu, när du fortsätter en Post enhet:

Post post1 = new Post();
post1.setId(1L);
post1.setTitle(
    "The High-Performance Java Persistence book is to be released!"
);

entityManager.persist(post1);

Hibernate kommer att köra följande SQL INSERT-satser:

Query:["INSERT INTO old_post (id, title, version) VALUES (?, ?, ?)"], Params:[(1, The High-Performance Java Persistence book is to be released!, 0)]

Query:["insert into post (created_on, title, version, id) values (?, ?, ?, ?)"], Params:[(2018-12-12, The High-Performance Java Persistence book is to be released!, 0, 1)]

När du gör en annan transaktion som uppdaterar en befintlig Post enhet och skapar en ny Post enhet:

Post post1 = entityManager.find(Post.class, 1L);
post1.setTitle(post1.getTitle().replace("to be ", ""));

Post post2 = new Post();
post2.setId(2L);
post2.setTitle(
    "The High-Performance Java Persistence book is awesome!"
);

entityManager.persist(post2);

Hibernate replikerar alla åtgärder till old_post tabell också:

 Query:["select tablerepli0_.id as id1_1_0_, tablerepli0_.created_on as created_2_1_0_, tablerepli0_.title as title3_1_0_, tablerepli0_.version as version4_1_0_ from post tablerepli0_ where tablerepli0_.id=?"], Params:[(1)]

 Query:["INSERT INTO old_post (id, title, version) VALUES (?, ?, ?)"], Params:[(2, The High-Performance Java Persistence book is awesome!, 0)]

 Query:["insert into post (created_on, title, version, id) values (?, ?, ?, ?)"], Params:[(2018-12-12, The High-Performance Java Persistence book is awesome!, 0, 2)]

 Query:["update post set created_on=?, title=?, version=? where id=? and version=?"], Params:[(2018-12-12, The High-Performance Java Persistence book is released!, 1, 1, 0)]

 Query:["UPDATE old_post SET title = ?, version = ? WHERE id = ?"], Params:[(The High-Performance Java Persistence book is released!, 1, 1)]

När du raderar ett Post enhet:

Post post1 = entityManager.getReference(Post.class, 1L);
entityManager.remove(post1);

old_post posten raderas också:

Query:["DELETE FROM old_post WHERE id = ?"], Params:[(1)]
Query:["delete from post where id=? and version=?"], Params:[(1, 1)]

Koden är tillgänglig på .