Hibernate Query cache - J2EE Reference

Query caching is one of the important features provided by Hibernate. I have explained the first level and second level caching in my previous article ( First level caching using hibernate, Second level caching ) ,When we need a particular query result has to be cached for future reference we can use query caching,

Let’s see how to configure query caching.

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/test</property>
        <property name="connection.username">root</property>
        <property name="connection.password">admin</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>
        <!-- Second-level cache  -->        
        <property name="cache.use_query_cache">true</property>
        <property name="cache.use_second_level_cache">true</property>       
        <property name="cache.provider_class">org.hibernate.cache.EhCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>        
        <property name="hbm2ddl.auto">validate</property> 
         <mapping/>
    </session-factory>
</hibernate-configuration>

<?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="connection.driver_class">com.mysql.jdbc.Driver</property>

<property name="connection.url">jdbc:mysql://localhost:3306/test</property>

<property name="connection.password">admin</property>

<property name="dialect">org.hibernate.dialect.MySQLDialect</property>

<property name="current_session_context_class">thread</property>

<property name="cache.provider_class">org.hibernate.cache.EhCacheProvider</property>

<property name="hbm2ddl.auto">validate</property>

</session-factory>

</hibernate-configuration>

Here we are adding the following lines to use query caching.

 <property name="cache.use_query_cache">true</property>
        <property name="cache.use_second_level_cache">true</property>       
        <property name="cache.provider_class">org.hibernate.cache.EhCacheProvider</property>

<property name="cache.provider_class">org.hibernate.cache.EhCacheProvider</property>

Entity class settings

package com.j2eereference.hibernate.queryCaching;

import javax.persistence.Cacheable;
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
@Cacheable
@Cache(usage = CacheConcurrencyStrategy.READ_ONLY)
@Table(name = "employee")
public class Employee {

	private int emp_id;
	private String emp_name;

	@Id
	@GeneratedValue
	@Column(name = "emp_id")
	public int getEmp_id() {
		return emp_id;
	}

	public void setEmp_id(int emp_id) {
		this.emp_id = emp_id;
	}

	@Column(name = "emp_name")
	public String getEmp_name() {
		return emp_name;
	}

	public void setEmp_name(String emp_name) {
		this.emp_name = emp_name;
	}

}

package com.j2eereference.hibernate.queryCaching;

import javax.persistence.Cacheable;

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

@Cacheable

@Cache(usage = CacheConcurrencyStrategy.READ_ONLY)

@Table(name = "employee")

public class Employee {

private int emp_id;

private String emp_name;

@Id

@GeneratedValue

@Column(name = "emp_id")

public int getEmp_id() {

return emp_id;

}

public void setEmp_id(int emp_id) {

this.emp_id = emp_id;

}

@Column(name = "emp_name")

public String getEmp_name() {

return emp_name;

}

public void setEmp_name(String emp_name) {

this.emp_name = emp_name;

}

We have to tell hibernate that a particular query result has to be set in the cache for future use. We can do this configuration as below .

package com.j2eereference.hibernate.queryCaching;

import java.util.List;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;

public class QueryCache {

	public static void main(String[] args) {
		AnnotationConfiguration config = new AnnotationConfiguration();
		config.addAnnotatedClass(Employee.class);
		SessionFactory sessionFactory = config.configure()
				.buildSessionFactory();
		Session session = sessionFactory.openSession();
		session.beginTransaction();

		Query query = session
				.createQuery("from Employee emp where emp.emp_id=1");
		query.setCacheable(true);
		List employees = query.list();
		session.getTransaction().commit();

		Session session2 = sessionFactory.openSession();
		session2.beginTransaction();

		Query query2 = session2
				.createQuery("from Employee emp where emp.emp_id=1");
		query2.setCacheable(true);
		List employees2 = query2.list();

		session2.getTransaction().commit();
	}
}

package com.j2eereference.hibernate.queryCaching;

import java.util.List;

import org.hibernate.Query;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.AnnotationConfiguration;

public class QueryCache {

public static void main(String[] args) {

AnnotationConfiguration config = new AnnotationConfiguration();

config.addAnnotatedClass(Employee.class);

SessionFactory sessionFactory = config.configure()

.buildSessionFactory();

Session session = sessionFactory.openSession();

session.beginTransaction();

Query query = session

.createQuery("from Employee emp where emp.emp_id=1");

query.setCacheable(true);

List employees = query.list();

session.getTransaction().commit();

Session session2 = sessionFactory.openSession();

session2.beginTransaction();

Query query2 = session2

.createQuery("from Employee emp where emp.emp_id=1");

query2.setCacheable(true);

List employees2 = query2.list();

session2.getTransaction().commit();

}

Output

Oct 16, 2012 8:49:30 PM org.hibernate.cache.StandardQueryCache 
INFO: starting query cache at region: org.hibernate.cache.StandardQueryCache
Oct 16, 2012 8:49:30 PM org.hibernate.cache.EhCacheProvider buildCache
WARNING: Could not find configuration [org.hibernate.cache.StandardQueryCache]; using defaults.
Hibernate: select employee0_.emp_id as emp1_0_, employee0_.emp_name as emp2_0_ from employee
employee0_ where employee0_.emp_id=1

Oct 16, 2012 8:49:30 PM org.hibernate.cache.StandardQueryCache

INFO: starting query cache at region: org.hibernate.cache.StandardQueryCache

Oct 16, 2012 8:49:30 PM org.hibernate.cache.EhCacheProvider buildCache

WARNING: Could not find configuration [org.hibernate.cache.StandardQueryCache]; using defaults.

Hibernate: select employee0_.emp_id as emp1_0_, employee0_.emp_name as emp2_0_ from employee

employee0_ where employee0_.emp_id=1

Here you can notice that hibernate has hit the DB only once . The second result is fetching from the cache.

setCacheable method is performing two roles.

If querycache is not already having the value, go to the database get the result, set the queryCache

For getting the queryCache without hitting the DB

Now lets see how the QueryCache is working with the below code .

I have explained the first level caching in my previous article ( First level caching using hibernate )

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