使用envers记录数据变更版本

序

hibernate的envers模块提供了一整套机制可以用来记录数据的变更。这里简单介绍一下。

1.自动配置

@SpringBootApplication
@EnableJpaRepositories(repositoryFactoryBeanClass = EnversRevisionRepositoryFactoryBean.class)
@EnableJpaAuditing(auditorAwareRef = "auditorAwareImpl")
public class EnversDemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(EnversDemoApplication.class, args);
    }
}

这里配置@EnableJpaRepositories(repositoryFactoryBeanClass = EnversRevisionRepositoryFactoryBean.class)表示开启envers模块。

2.Audited注解

@Entity
@Audited
public class Book extends AuditableEntity{

    @javax.persistence.Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String title;

    private String author;

    private String description;

    private long price;

    private boolean valid;

    // getter and setter
}

使用@Audited标注一下这个实体类需要审计。

继承RevisionRepository

public interface BookDao extends RevisionRepository<Book, Long, Integer>,JpaRepository<Book, Long> {
}

通过继承RevisionRepository获取查找revisions的查询方法，主要如下：

@NoRepositoryBean
public interface RevisionRepository<T, ID extends Serializable, N extends Number & Comparable<N>> {
    Revision<N, T> findLastChangeRevision(ID var1);

    Revisions<N, T> findRevisions(ID var1);

    Page<Revision<N, T>> findRevisions(ID var1, Pageable var2);

    Revision<N, T> findRevision(ID var1, N var2);
}

这里的N是指变更版本号的类型，一般Integer够用，如果觉得不够用可以改为Long类型。这里的T就是实体类。ID就是实体类的主键类型。

查询变更

经过以上配置之后，就可以正常记录变更的每个版本了，可以通过如下方法来查询，比如：

Revisions<Integer,Book> revision = bookDao.findRevisions(id);
List<Revision<Integer,Book>> data = revision.getContent();

这里的id为实体的id

revision的表结构

hibernate默认以实体类后缀_AUD来记录每个变更的版本，比如

-- ----------------------------
--  Table structure for book_aud
-- ----------------------------
DROP TABLE IF EXISTS "public"."book_aud";
CREATE TABLE "public"."book_aud" (
    "id" int8 NOT NULL,
    "rev" int4 NOT NULL,
    "revtype" int2,
    "author" varchar(255) COLLATE "default",
    "description" varchar(255) COLLATE "default",
    "price" int8,
    "title" varchar(255) COLLATE "default",
    "valid" bool
)
WITH (OIDS=FALSE);
ALTER TABLE "public"."book_aud" OWNER TO "postgres";

-- ----------------------------
--  Primary key structure for table book_aud
-- ----------------------------
ALTER TABLE "public"."book_aud" ADD PRIMARY KEY ("id", "rev") NOT DEFERRABLE INITIALLY IMMEDIATE;

-- ----------------------------
--  Foreign keys structure for table book_aud
-- ----------------------------
ALTER TABLE "public"."book_aud" ADD CONSTRAINT "fk2u9iq76nh69r6f989ae7xft9" FOREIGN KEY ("rev") REFERENCES "public"."revinfo" ("rev") ON UPDATE NO ACTION ON DELETE NO ACTION NOT DEFERRABLE INITIALLY IMMEDIATE;

如果想改表后缀的话，可以通过org.hibernate.envers.audit_table_suffix的属性进行配置。里头的rev字段表示revision的版本号，一般全局递增。revtype字段表示操作类型，0表示新增，1表示更新，2表示删除。

另外还有一个表是revinfo，记录每个变更的版本号和时间：

-- ----------------------------
--  Table structure for revinfo
-- ----------------------------
DROP TABLE IF EXISTS "public"."revinfo";
CREATE TABLE "public"."revinfo" (
    "rev" int4 NOT NULL,
    "revtstmp" int8
)
WITH (OIDS=FALSE);
ALTER TABLE "public"."revinfo" OWNER TO "postgres";

-- ----------------------------
--  Primary key structure for table revinfo
-- ----------------------------
ALTER TABLE "public"."revinfo" ADD PRIMARY KEY ("rev") NOT DEFERRABLE INITIALLY IMMEDIATE;

自定义revision entity

如果默认的envers的实现不满足你的要求的话，使用@RevisionEntity注解，替换@Audited，然后自定义listener，比如

@Entity
@RevisionEntity( ExampleListener.class )
public class ExampleRevEntity extends DefaultRevisionEntity {
    private String username;

    public String getUsername() { return username; }
    public void setUsername( String username ) { this.username = username; }
}
public class ExampleListener implements RevisionListener {

    public void newRevision( Object revisionEntity ) {
        ExampleRevEntity exampleRevEntity = ( ExampleRevEntity ) revisionEntity;
        Identity identity =
            (Identity) Component.getInstance( "org.jboss.seam.security.identity" );

        exampleRevEntity.setUsername( identity.getUsername() );
    }
}

具体的这里就不细讲了，具体可以参考hibernate。

doc

envers