Hibernate Second Level cache Demonstration

 Here we demonstrate the second level cache of hibernate using ehcache.Here in this example we are using one entity student and READ_ONLY cache strategy to handle cache.

 StudentInfo.java

package com.nik.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;
import org.hibernate.annotations.Cache;
import org.hibernate.annotations.CacheConcurrencyStrategy;

@Entity
@Table(name = "student")
@Cache(usage=CacheConcurrencyStrategy.READ_ONLY,region="studentCache")

public class StudentInfo implements java.io.Serializable {
   @Id
   @GeneratedValue
   @Column(name = "student_id")
    private long studentId;

   @Column(name = "student_name")
    private String studentName;

    public StudentInfo() {
    }

    public StudentInfo(String studentName) {
        this.studentName = studentName;
    }

    public long getStudentId() {
        return this.studentId;
    }

    public void setStudentId(long studentId) {
        this.studentId = studentId;
    }

    public String getStudentName() {
        return this.studentName;
    }

    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }

}

Hibernate configuration file is as follows:

hibenate.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 name="">
  <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
  <property name="hibernate.connection.url">jdbc:mysql://localhost/testdb</property>
  <property name="hibernate.connection.username">root</property>
  <property name="connection.password">*********</property>
  <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
  <property name="hibernate.show_sql">true</property>
  <property name="hbm2ddl.auto">create</property>
<property name="hibernate.cache.region.factory_class">org.hibernate.cache.ehcache.EhCacheRegionFactory</property>
              
         <!-- enable second level cache and query cache -->
         <property name="hibernate.cache.use_second_level_cache">true</property>
         <property name="hibernate.cache.use_query_cache">true</property>
          <property name="net.sf.ehcache.configurationResourceName">/ehcache.xml</property>
  <mapping class="com.nik.model.StudentInfo" />
   
 </session-factory>
</hibernate-configuration>



ehcache.xml

<?xml version="1.0" encoding="UTF-8"?>
<ehcache xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:noNamespaceSchemaLocation="ehcache.xsd" updateCheck="true"
    monitoring="autodetect" dynamicConfig="true">

    <diskStore path="java.io.tmpdir/ehcache" />

    <defaultCache maxEntriesLocalHeap="10000" eternal="false"
        timeToIdleSeconds="120" timeToLiveSeconds="120" diskSpoolBufferSizeMB="30"
        maxEntriesLocalDisk="10000000" diskExpiryThreadIntervalSeconds="120"
        memoryStoreEvictionPolicy="LRU" statistics="true">
        <persistence strategy="localTempSwap" />
    </defaultCache>

    <cache name="studentCache" maxEntriesLocalHeap="10000" eternal="false"
        timeToIdleSeconds="5" timeToLiveSeconds="10">
        <persistence strategy="localTempSwap" />
    </cache>

    <cache name="org.hibernate.cache.internal.StandardQueryCache"
        maxEntriesLocalHeap="5" eternal="false" timeToLiveSeconds="120">
        <persistence strategy="localTempSwap" />
    </cache>

</ehcache>

HibernateUtil.java

package com.nik.util;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;

public class HibernateUtil {
  
    private static SessionFactory sessionFactory;
  
     private static SessionFactory buildSessionFactory() {
            try {
                // Create the SessionFactory from hibernate.cfg.xml
                Configuration configuration = new Configuration();
                configuration.configure("hibernate.cfg.xml");
                ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
                SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
                return sessionFactory;
            }
            catch (Throwable ex) {
                System.err.println("SessionFactory creation failed." + ex);
                ex.printStackTrace();
                throw new ExceptionInInitializerError(ex);
            }
        }
       
        public static SessionFactory getSessionFactory() {
            if(sessionFactory == null) sessionFactory = buildSessionFactory();
            return sessionFactory;
        }
}


StudentServiceImpl.java

package com.nik.dao;
import org.hibernate.Session;
import org.hibernate.SessionFactory;

import com.nik.model.StudentInfo;
import com.nik.util.HibernateUtil;

public class StudentServiceImpl {
    public static void main(String[] arg){
         SessionFactory sf = HibernateUtil.getSessionFactory(); 
         Session session = sf.openSession(); 
          
         session.beginTransaction(); 
          
         StudentInfo student = new StudentInfo(); 
         student.setStudentName("Nitesh Sahay");
          
             
         session.save(student); 
          
         session.getTransaction().commit(); 
         StudentInfo stu=(StudentInfo) session.load(StudentInfo.class, 1l);
         System.out.println(stu.getStudentName());
         session.close();
         session = sf.openSession();
         session.evict(stu); //evict student from 1st level cache if any
         session.clear();//clear 1st level cache
         stu=(StudentInfo) session.load(StudentInfo.class, 1l);
        
         System.out.println(stu.getStudentName());
        
         System.out.println(stu.getStudentName());
         session.close();
         sf.close();
        }



}

Output: