Hibernate – Envers – Easy Auditing for Entity Classes

Have you tracked your Entity Objects ? When it has created,modified and deleted with time.

Try Envers for Easy Auditing of Entity Classes. Very simple to audit your Entity classes using @Audited. Envers now becomes a part of Hibernate 3.5.

List of libraries you need for this

• hibernate3.jar
• antlr.jar
• commons-collections.jar
• dom4j-1.6.1.jar
• javassist.jar
• jpa-api-2.0-1.jar
• jta.jar
• mysql-connector-java-5.1.3-rc-bin.jar
• slf4j-api-1.6.1.jar

1. hibernate.cfg.xml

Add the Audit Event Listeners in your hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- Database connection settings -->
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost:3306/envers</property>
<property name="connection.username">root</property>
<property name="connection.password">welcome123</property>
<!-- JDBC connection pool (use the built-in) -->
<property name="connection.pool_size">1</property>
<!-- SQL dialect -->
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<!-- Enable Hibernate's automatic session context management -->
<property name="current_session_context_class">thread</property>
<!-- Disable the second-level cache -->
<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
<!-- Echo all executed SQL to stdout -->
<property name="show_sql">true</property>
<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">update</property>
<mapping/>
<!-- Hibernate ENVERS Listener Configuration -->
<listener class="org.hibernate.envers.event.AuditEventListener" type="post-insert"/>
<listener class="org.hibernate.envers.event.AuditEventListener" type="post-update"/>
<listener class="org.hibernate.envers.event.AuditEventListener" type="post-delete"/>
<listener class="org.hibernate.envers.event.AuditEventListener" type="pre-collection-update"/>
<listener class="org.hibernate.envers.event.AuditEventListener" type="pre-collection-remove"/>
<listener class="org.hibernate.envers.event.AuditEventListener" type="post-collection-recreate"/>
</session-factory>
</hibernate-configuration>

2. Entity Class

Your Entity class should have @Audited for tracking the values in the persistent class.

package com;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
import org.hibernate.envers.Audited;

/**
* @author Anand
*
*/
@Entity
@Table(name="user")
@Audited //---------------- This is more important!!!!!!!!
public class User implements Serializable {
@Id
@GeneratedValue
@Column(name="id")
private int id;
@Column(name="firstname")
private String firstname;
@Column(name="lastname")
private String lastname;
@Column(name="email")
private String email;
/**
* @return the email
*/
public String getEmail() {
return email;
}
/**
* @param email the email to set
*/
public void setEmail(String email) {
this.email = email;
}
/**
* @return the firstname
*/
public String getFirstname() {
return firstname;
}
/**
* @param firstname the firstname to set
*/
public void setFirstname(String firstname) {
this.firstname = firstname;
}
/**
* @return the id
*/
public int getId() {
return id;
}
/**
* @param id the id to set
*/
public void setId(int id) {
this.id = id;
}
/**
* @return the lastname
*/
public String getLastname() {
return lastname;
}
/**
* @param lastname the lastname to set
*/
public void setLastname(String lastname) {
this.lastname = lastname;
}
}

3. DB Structure of your Entity class

Field	Type	Null	Key	Default	Extra
id	int(11)	NO	PRI	NULL	auto_increment
firstname	varchar(128)	YES		NULL
lastname	varchar(128)	YES		NULL
email	varchar(64)	YES		NULL

4. Insert the data
Now lets begin with Insert the data
Add the data to your Entity Class

User user = new User();
user.setFirstname("biju");
user.setLastname("cd");
user.setEmail("cdbiju@gmail.com");

Get the Session Factory and Session to save the data into DB

/** Getting the Session Factory and session */
//SessionFactory sessionfactory = HibernateUtil.getSessionFactory();
SessionFactory sessionfactory = new AnnotationConfiguration().configure().buildSessionFactory();
Session sess = sessionfactory.getCurrentSession();
/** Starting the Transaction */
Trans)action tx = sess.beginTransaction();
/** Saving POJO */
sess.save(user);
/** Commiting the changes */
tx.commit();
System.out.println("Record Inserted");
/** Closing Session */
sessionfactory.close();

5. New Tables Created for holding the Revision Entries

Table 1 : user_aud(Audit Table)

Audit table will have the default suffix to be _aud and present in the default schema of the database.
It has the same structure as the Entity table. Additionally it has three columns in it namely

1. id
2. REV
3. REVINFO

Field	Type	Null	Key	Default	Extra
id	int(11)	NO	PRI	NULL	auto_increment
REV	int(11)	NO	PRI	NULL
REVTYPE	tinyint(11)	YES
firstname	varchar(128)	YES		NULL
lastname	varchar(128)	YES		NULL
email	varchar(64)	YES		NULL

Table 2 : revinfo(common table for the Entity)

This revinfo table will be common for all the Entity classes. 

Field	Type	Null	Key	Default	Extra
REV	int(11)	NO	PRI	NULL	auto_increment
REVTSTMP	bigint(20)	YES

This two tables will be automatically created. 

6. Entries in the Audit table and Revinfo table after insert

id	REV	REVTYPE	email	firstname	lastname
1	1	0	cdbiju@gmail.com	biju	cd

Here the id column is foreign key for the entity class “user”, REV will be primary key for the audited table. More Importantly the REVTYPE has three values in it.

0 = Creation

1 = Update

2 = Delete

Whenever the insertion takes for the entity class “user”,  it makes an entry as Zero and keeps all the  Audited columns values in it. (0 = Creation)

Look into Revinfo table

REV	REVTSTMP
1	134343453534434

It contains the Revision Timestamp value.

7. Update the data and Look into Audit Tables

User user = new User();
user.setId(1);   // Passes the id=1 to the Entity Class

/** Getting the Session Factory and session */
SessionFactory sessionfactory = HibernateUtil.getSessionFactory();
Session sess = sessionfactory.getCurrentSession();
/** Starting the Transaction */
Transaction tx = sess.beginTransaction();
User u = (User) sess.get(User.class, user.getId());
u.setFirstname("biju-append");
u.setLastname("cd-append");
u.setEmail("cdbiju-append@gmail.com");
sess.saveOrUpdate(u);
/** Commiting the changes */
tx.commit();
System.out.println("Record Updated");
/** Closing Session */
sessionfactory.close();

Look into the Audit Table

id	REV	REVTYPE	email	firstname	lastname
1	1	0	cdbiju@gmail.com	biju	Cd
1	2	1	cdbiju-append@gmail.com	biju-append	cd-append

Note 1 is for Update (REVTYPE)

REV	REVTSTMP
1	134343453534434
2	134343453534434

When we update the same record, it updates the Audited columns values and update the REVTYPE to be 1.( 1 = Updation)

8. Delete the data and Look into Audit Tables

User user = new User();
user.setId(1);   // Passes the id=1 to the Entity Class to delete

/** Getting the Session Factory and session */
SessionFactory sessionfactory = HibernateUtil.getSessionFactory();
Session sess = sessionfactory.getCurrentSession();
/** Starting the Transaction */
Transaction tx = sess.beginTransaction();
User u = (User) sess.get(User.class, user.getId());
sess.delete(u);
/** Commiting the changes */
tx.commit();
System.out.println("Record Deleted");
/** Closing Session */
sessionfactory.close();

Look into the Audit Table

id	REV	REVTYPE	email	firstname	lastname
1	1	0	cdbiju@gmail.com	biju	Cd
1	2	1	cdbiju-append@gmail.com	biju-append	cd-append
1	3	2	NULL	NULL	NULL

Note 2 is for Delete (REVTYPE)

REV	REVTSTMP
1	134343453534434
2	134343453534434
3	134343452343243

When the data is Deleted, the row has been deleted in the Entity table . But in the Audited Table, it updates all the Audited columns to be NULL and updates the REVTYPE to be 2.(2 = Delete)