Manage a Cache System with EHCache

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Posted the 2008 May, 22 by admin

The implementation of an Application cache is always a task which needs to impact many peoples and ressources to be done. EHCache is a simple and fast solution to implement, easy to connect with any existing application.

here is a sale-pitch which in my mind, defines the best EHCache:

“Ehcache is a pure Java, in-process cache”, “Available under the Apache 1.1 license. Ehcache’s copyright and licensing has been reviewed and approved by the Apache Software Foundation, making ehcache suitable for use in Apache projects.”

1) Dependencies:

EHCache JAR, For now : ehcache-1.1.jar.
Log4J JAR, For now : log4j-1.2.9.jar.
Jakarta Commons Collections : http://jakarta.apache.org/commons/collections/.
Jakarta Commons Loggins : http://jakarta.apache.org/commons/logging/

2) Configuring the logging service (In this tutorial log4j) :

Fichier : WEB-INF/log4j.properties

# Set root logger level to DEBUG and its only appender to A1.
log4j.rootLogger=DEBUG, A1
 
# A1 is set to be a ConsoleAppender.
log4j.appender.A1=org.apache.log4j.ConsoleAppender
 
# A1 uses PatternLayout.
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n

Please, note that for moving the application to a production server, we have to change the alerting level to avoid logging debug and info messages.

3) Creation of a sample serialyzable object to cache :

Fichier : Movie.java

/*
 * Created on 22 avr. 2005
 *
 */
 package com.tellaw.ehCacheSample;
 
 import java.io.Serializable;
 
 /**
 * @author Eric
 *
 */
 public class Movie implements Serializable {
 
	private String name = "";
	private String description = "";
	private String actor = "";
 
	public Movie () {
		// Default constructor.	
	}
 
	public String getActor() {
		return actor;
	}
 
	public void setActor(String actor) {
		this.actor = actor;
	}
 
	public String getDescription() {
		return description;
	}
 
	public void setDescription(String description) {
		this.description = description;
	}
 
	public String getName() {
		return name;
	}
 
	public void setName(String name) {
		this.name = name;
	}
}

4) External file configuration dedicated to EHCache :

Fichier : WEB-INF/ehCache.xml

5) Creating a test servlet which will try to load Objects from EHCache :

Fichier : TestServlet.java

/*
 * Created on 22 avr. 2005
 *
 */
 package com.tellaw.ehCacheSample.servlets;
 
 import java.io.IOException;
 import java.io.PrintWriter;
 
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import org.apache.log4j.Logger;
 import org.apache.log4j.PropertyConfigurator;
 import net.sf.ehcache.*;
 
 import com.tellaw.ehCacheSample.*;
 
 /**
 * @author Eric
 *
 */
 
 public class TestServlet extends HttpServlet {
 
	private static Logger logger = Logger.getLogger(TestServlet.class.getName());
 
	private CacheManager manager = null;
	private Cache cache = null;
 
	public void init() throws ServletException {
 
		// Configuration de log4J.
		PropertyConfigurator.configure( getServletContext().getRealPath ("WEB-INF/log4j.properties") );
 
		// Creating the cache manager from configuration file
		try {
			manager = CacheManager.create(getServletContext().getRealPath ("WEB-INF/ehCache.xml"));
			cache = manager.getCache("sampleCache1");
		} catch (Exception e) {
			logger.error("Unable to load EHCACHE configuration file");
		}
 
	}
 
	public void destroy() {}
 
	protected void doPost(HttpServletRequest arg0, HttpServletResponse arg1) throws ServletException, IOException {
		doGet(arg0, arg1);
	}
 
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
		// Output Writer creation		
		PrintWriter out = response.getWriter();
 
		// Creation of a test Movie Object
		Movie myMovie = new Movie ();
		myMovie.setName("The Ring");
		myMovie.setDescription("Film fantastique");
		myMovie.setActor("Naomi Watts");
 
		// Caching this element
		// Attention ce que la classe Movie implémente java.io.Serializable
		Element element = new Element(myMovie.getName(), myMovie);
		cache.put(element);
 
		out.println ("Objet mis en cache<br/>");
 
		// Reading the cache
		try {
			element = cache.get("The Ring");
		} catch (Exception e) {}
 
		Movie mySecondMovie = (Movie)element.getValue();
 
		out.println("<br/><br/>Cache loaded into the object mySecondMovie<br/>");
		out.println("Name : " + mySecondMovie.getName() +"<br/>");
		out.println("Description : " + mySecondMovie.getDescription() +"<br/>");
		out.println("Actor : " + mySecondMovie.getActor() +"<br/>");
	}
}

6) Web.xml File used to map the servlet :

Fichier : WEB-INF/web.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app 	xmlns="http://java.sun.com/xml/ns/j2ee"
			xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
			xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
			version="2.4">
	<display-name>ehCacheSample</display-name>
	<description>
		EHCache tutorial from tellaw.org
	</description>
 
	<!-- Declaration des servlets -->
	<servlet>
		<servlet-name>MovieServlet</servlet-name>
		<servlet-class>com.tellaw.ehCacheSample.servlets.TestServlet</servlet-class>
	</servlet>
 
	<!-- Declaration du mapping -->
	<servlet-mapping>
		<servlet-name>MovieServlet</servlet-name>
		<url-pattern>/MovieServlet</url-pattern>
	</servlet-mapping>
</web-app>

Notes :

The official documentation doesn’t ask to provide Jakarta Commons Collections as a dependency..
Please do not forget to change the logging level of the application when deploying on production platforms.

Sites utiles :

Le site de ehCache : ehcache

Tags: Java //

Manage a Cache System with EHCache

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