如何使用 JPA 和 Hibernate 复制 INSERT/UPDATE/DELETE 语句

Question

我想以我的系统可恢复的方式重命名 PostgreSQL (9.6) table（使用 JPA/Hibernate 的 java 应用程序）

在我的 java 代码中，JPA 实体将具有以下注释 @Entity @Table(name="old_name") 并且数据库将具有等效的 table 称为 old_name .

我想以一种可以增量更新数据库和 java 应用程序的方式将 table 重命名为 new_name，允许失败和回滚。

典型的步骤是

在 new_name

old_name

确保read/writes在两种方式中都可用（即数据被双向复制）
更新 java 应用程序以使用新的 table new_name
当自信的系统更新完成后，删除 old_name

实际上，我想要在具有相同数据的相同模式中复制 table，两者都能够接受读取和写入，可以从 JPA 实体中读取。

我知道触发器的使用，并希望避免这种情况。我希望有一种我不知道也没有发现的技术可以使这比使用触发器更不痛苦。

我试图重命名 table 并在其上创建一个 "simple view"，但是 JPA 实体抱怨说它找不到具有视图名称的 table . （因为它是一个视图，而不是 table :) 并且似乎没有 @View/@Table JPA 注释可以处理这个问题）

我还没有尝试过这里列出的设施：http://wiki.postgresql.org/wiki/Replication,_Clustering,_and_Connection_Pooling 因为大多数似乎都是关于池化、分片的，我需要一个简单的短期 table 副本，但我会的也在调查这些。

谢谢 - 我当然想要最简单的选项，更喜欢 postgres/JPA 内置的东西，但也会认真考虑第 3 方选项。

Answer 1

数据库tables

假设您有以下两个 table：

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 实体

old_post table 必须用较新的 post 复制。请注意 post table 现在比旧的 table.

有更多的列

我们只需要映射 Post 个实体：

@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
}

Hibernate 事件侦听器

现在，我们必须注册 3 个事件侦听器来拦截 Post 实体的 INSERT、UPDATE 和 DELETE 操作。

我们可以通过以下事件侦听器执行此操作：

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;
    }
}

可以使用 Hibernate 注册 3 个事件侦听器 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) {

    }
}

并且，要指示 Hibernate 使用此自定义 Integrator，您需要设置 hibernate.integrator_provider 配置属性:

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

测试时间

现在，当持久化 Post 实体时：

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

entityManager.persist(post1);

Hibernate 将执行以下 SQL INSERT 语句：

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)]

当执行另一个更新现有 Post 实体并创建新 Post 实体的事务时：

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 也将所有操作复制到 old_post table：

 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)]

删除 Post 个实体时：

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

old_post条记录也被删除：

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

代码可用 GitHub。

如何使用 JPA 和 Hibernate 复制 INSERT/UPDATE/DELETE 语句

How to replicate INSERT/UPDATE/DELETE statements using JPA and Hibernate

java

postgresql

replication

hibernate

jpa

数据库tables

JPA 实体

Hibernate 事件侦听器

测试时间