Java Technologies: increment persistence operation in hibernate

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This algorithm generated identity values of type long or short or int that are unique. This algorithm works with all database software but can generate only numeric values as identity values. The class name of this algorithm is “org.hibernate.id.IncrementGenerator”. This uses “(Max identity value + 1) as the formula to generate next identity value.

This generator supports in all the databases, database independent
This generator is used for generating the id value for the new record by using the formula

Max of id value in Database + 1

if we manually assigned the value for primary key for an object, then hibernate doesn’t considers that value and uses max value of id in database + 1 concept only
If there is no record initially in the database, then for the first time this will saves primary key value as 1, as…

max of id value in database + 1
0 + 1
result -> 1

Here is the example code to test Increment algorithm functionality :

This is hibernate.cfg.xml file for connecting the postgreSQL database.

 <?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> <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property> 
		hibernate word is optional <property name="connection.url">jdbc:oracle:thin:@localhost:1521:ORCL</property> 
		<property name="hibernate.connection.username">kcv</property> <property name="hibernate.connection.password">kcv</property> 
		<property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property> 
		<property name="show_sql">true</property> <mapping resource="Employee.hbm.xml"/> 
		</session-factory> -->
   <session-factory>
      <property name="hibernate.current_session_context_class">thread</property>
      <property name="hbm2ddl.auto">create</property>
      <property name="dialect">org.hibernate.dialect.PostgreSQLDialect</property>
      <property name="connection.url">jdbc:postgresql://localhost:5432/hibernate</property>
      <property name="connection.username">postgres</property>
      <property name="connection.password">password</property>
      <property name="connection.driver_class">org.postgresql.Driver</property>
      <property name="show_sql">true</property>
      <property name="format_sql">true</property>
      <property name="use_sql_comments">true</property>
      		<mapping resource="EmployeeBean.hbm.xml" />
   </session-factory>
</hibernate-configuration>

This is EmployeeBean.hbm.xml mapping file for map the Entity(POJO) class to columns.

 <?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
	<class name="com.cv.hibernate.algorithm.model.EmployeeBean"
		table="EMPLOYEE_INC">
		<id name="id" type="java.lang.Long"> 
			<column name="EID" precision="10" scale="0" />
			 <generator class="increment" />
			 </id>
		<property name="firstName" type="java.lang.String">
			<column name="FIRSTNAME" length="29" not-null="true" />
		</property>
		<property name="lastName" type="java.lang.String">
			<column name="LASTNAME" length="29" not-null="true" />
		</property>
		<property name="email" type="java.lang.String">
			<column name="EMAIL" length="39" not-null="true" />
		</property>
	</class>
</hibernate-mapping>

This is Increment.java main class having the application business logic.

 
    
package com.cv.hibernate.algorithm;



import org.apache.log4j.Logger;

import org.hibernate.Session;



import com.cv.hibernate.algorithm.model.EmployeeBean;

import com.cv.hibernate.algorithm.util.HibernateUtil;



/**

 * @author Chandra Vardhan

 */

public class Increment {



  private final static Logger logger = Logger.getLogger(Increment.class);



  public static void main(String args[]) throws Exception {



    Session ses = HibernateUtil.getSession();

    EmployeeBean eb = new EmployeeBean();

    // eb.setEid(new Long(115)); //For the Increment algorithm we need not

    // to

    // write setEid(-) method...

    eb.setFirstName("chandra");

    eb.setLastName("vardhan");

    eb.setEmail("meetkodam@gmail.com");

    ses.beginTransaction();

    ses.saveOrUpdate(eb);

    logger.info("Saved successful... ");

    ses.getTransaction().commit();

    HibernateUtil.closeSession();

  }



}

This is EmployeeBean.java Entity(POJO) class having the fields needs to be configured in mapping file.

 
    
package com.cv.hibernate.algorithm.model;



/**

 * @author Chandra Vardhan

 */

public class EmployeeBean {

  private Long id;

  private String firstName;

  private String lastName;

  private String email;



  public Long getId() {

    return id;

  }



  public void setId(Long id) {

    this.id = id;

  }



  public String getFirstName() {

    return firstName;

  }



  public void setFirstName(String firstName) {

    this.firstName = firstName;

  }



  public String getLastName() {

    return lastName;

  }



  public void setLastName(String lastName) {

    this.lastName = lastName;

  }



  public String getEmail() {

    return email;

  }



  public void setEmail(String email) {

    this.email = email;

  }



}

This is HibernateUtil.java utility class for getting the database connection.

 
    
package com.cv.hibernate.algorithm.util;



import org.apache.log4j.Logger;

import org.hibernate.HibernateException;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.boot.registry.StandardServiceRegistryBuilder;

import org.hibernate.cfg.Configuration;



import com.cv.hibernate.algorithm.model.EmployeeBean;



/**

 * Configures and provides access to Hibernate sessions, tied to the current

 * thread of execution. Follows the Thread Local Session pattern, see

 * {@link http://hibernate.org/42.html }.

 */

public class HibernateUtil {

  private final static Logger logger = Logger.getLogger(HibernateUtil.class);



  /**

   * Location of hibernate.cfg.xml file. Location should be on the classpath

   * as Hibernate uses #resourceAsStream style lookup for its configuration

   * file. The default classpath location of the hibernate config file is in

   * the default package. Use #setConfigFile() to update the location of the

   * configuration file for the current session.

   */

  private static String CONFIG_FILE_LOCATION = "hibernate.cfg.xml";

  private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();

  private static Configuration configuration = new Configuration();

  private static SessionFactory sessionFactory;



  



  static {

    try {

      configuration = configuration.configure(CONFIG_FILE_LOCATION);

      StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder()

          .applySettings(configuration.getProperties());

      sessionFactory = configuration.buildSessionFactory(builder.build());

      logger.info("%%%% Connection successful %%%%");

    } catch (Exception e) {

      logger.error("%%%% Error Creating SessionFactory %%%%");

      e.printStackTrace();

    }

  }



  private HibernateUtil() {

  }



  /**

   * Returns the ThreadLocal Session instance. Lazy initialize the

   * <code>SessionFactory</code> if needed.

   *

   * @return Session

   * @throws HibernateException

   */

  public static Session getSession() throws HibernateException {

    Session session = (Session) threadLocal.get();



    if (session == null || !session.isOpen()) {

      if (sessionFactory == null) {

        rebuildSessionFactory();

      }

      session = (sessionFactory != null) ? sessionFactory.openSession() : null;

      threadLocal.set(session);

    }



    return session;

  }



  /**

   * Rebuild hibernate session factory

   *

   */

  public static void rebuildSessionFactory() {

    try {

      configuration = configuration.configure(CONFIG_FILE_LOCATION);

      StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder()

          .applySettings(configuration.getProperties());

      sessionFactory = configuration.buildSessionFactory(builder.build());

      logger.info("%%%% Connection successful %%%%");

    } catch (Exception e) {

      logger.error("%%%% Error Creating SessionFactory %%%%");

      e.printStackTrace();

    }

  }



  /**

   * Close the single hibernate session instance.

   *

   * @throws HibernateException

   */

  public static void closeSession() throws HibernateException {

    Session session = (Session) threadLocal.get();

    threadLocal.set(null);



    if (session != null) {

      session.close();

      System.exit(0);

    }

  }



  /**

   * return session factory

   *

   */

  public static SessionFactory getSessionFactory() {

    return sessionFactory;

  }



  /**

   * return hibernate configuration

   *

   */

  public static Configuration getConfiguration() {

    return configuration;  

  }

  public static void saveOrUpdate() {

    Session ses = getSession();

    EmployeeBean eb = new EmployeeBean();

    eb.setId(new Long(101));

    eb.setFirstName("chandra");

    eb.setLastName("vardhan");

    eb.setEmail("meetkodam@gmail.com");

    ses.beginTransaction();

    ses.saveOrUpdate(eb);

    logger.info("Saved successful...");

    ses.getTransaction().commit();

    ses.close();

  }

}

This is log4j.properties file having the entries for logging the information into the console/file.

#By default enabling Console appender

# Root logger option

log4j.rootLogger=INFO, stdout

# Redirect log messages to console

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.appender.stdout.Target=System.out

log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

log4j.appender.stdout.layout.ConversionPattern=%-5p [%c]:%L -->> %m%n

# Redirect log messages to a log file

#log4j.appender.file=org.apache.log4j.RollingFileAppender

#log4j.appender.file.File=C:\\servlet-application.log

#log4j.appender.file.MaxFileSize=5MB

#log4j.appender.file.MaxBackupIndex=10

#log4j.appender.file.layout=org.apache.log4j.PatternLayout

#log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

This is pom.xml file having the entries of dependency jars and information to build the application .

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.cv.hibernate.algorithm</groupId>
  <artifactId>algorithms</artifactId>
  <version>1.0</version>
 <dependencies>
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-entitymanager</artifactId>
			<version>4.3.5.Final</version>
		</dependency>
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-c3p0</artifactId>
			<version>4.3.5.Final</version>
		</dependency>

		<dependency>
			<artifactId>hibernate-core</artifactId>
			<groupId>org.hibernate</groupId>
			<version>4.3.5.Final</version>
		</dependency>

		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-validator</artifactId>
			<version>4.2.0.Final</version>
		</dependency>
		<dependency>
			<groupId>org.hibernate.common</groupId>
			<artifactId>hibernate-commons-annotations</artifactId>
			<version>4.0.4.Final</version>
		</dependency>
		<dependency>
			<groupId>org.hibernate.javax.persistence</groupId>
			<artifactId>hibernate-jpa-2.0-api</artifactId>
			<version>1.0.1.Final</version>
		</dependency>

		<dependency>
			<groupId>javax.validation</groupId>
			<artifactId>validation-api</artifactId>
			<version>1.0.0.GA</version>
			provided
		</dependency>
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-api</artifactId>
			<version>1.6.4</version>
		</dependency>
		<dependency>
			<groupId>org.jboss.logging</groupId>
			<artifactId>jboss-logging</artifactId>
			<version>3.1.0.CR2</version>
		</dependency>
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-log4j12</artifactId>
			<version>1.6.4</version>
		</dependency>
		<dependency>
			<groupId>postgresql</groupId>
			<artifactId>postgresql</artifactId>
			<version>9.1-901.jdbc4</version>
		</dependency>
		
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-simple</artifactId>
			<version>1.7.5</version>
		</dependency>
	</dependencies>
	<build>

		<plugins>
			<plugin>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.3</version>
				<configuration>
					<source>1.8</source>
					<target>1.8</target>
				</configuration>
			</plugin>
		</plugins>
	</build>
</project>

Java Technologies

increment persistence operation in hibernate