Java Caching

JAVA AND CACHING

6/26/2009

By Martin Nad [email protected]

Java and cashing

Java and caching [TYPE THE SUBTITLE]

OVERVIEW Here I want to show why and you should use cache, and presents some different kind of caching system in java, and give you an example by on chaching system.

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TABLE OF CONTEXT Foreword Caching Different kind of caching in java ehCache example

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FORWORD When we are working with the large information and retrieve too much information or data, we need a mechanism to get retrieve faster information. Caching is one way to optimize the access time to retrieve information. Especially when we use the database, and we have too much traffic between database and application, we can use caching to reduce the traffic to the database. If we use the third-party application to get data, we can also use caching here to reduce traffic and save lot of the time. Usually, the third-party application is outside of the local network, and it takes more time to get data from third-party application. And certainly, they use some database too. There are many different situation that you can use caching and you shouldn’t use caching in all cases either. Here I will discuss about general caching and how to use it in your application and with the database and using with the Hibernate.

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CACHING Caching system is a smart way to reduce the response time of your application. You can use caching in different area, in your application, in your database level, or using cache with the Hibernate If you use hibernate, hibernate uses two differ nets caching level. 1-first level cache 2-second level cache A discussion I had with one of my colleges, I told him, Hibernate reduce the database-connection and database traffic, and he was against to it, and he told he has test and checked the database log and noticed that the database connection was extremely high with hibernate. It sounds odd. And it doesn’t agree with any documentation and books that I have read. I believe he had some configuration-problem with his hibernate. It is not important which tools, technology or method you are using, it is most important you use those tools, technology or method, in right way. Not just use Hibernate, because everybody talks about it, or if it is poplar and so on. If you don’t know how you can use the Hibernate, it should cost you much more time and resource. Even I think it is very easy to use. Maintains of it, update your application all of them cost time. Especially if you use the tools in wrong way, it should

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cost you much more. I have noticed it in almost my documentation about it. Anyway, the first level cache is using by Session object. Hibernate use this level as cache as default. It will reduce the number of sql-queries. One example: if you use several update with the same transaction, hibernate will just update once for all modification at the end of the transaction. And the second level cache is using by Session Factory object. This kind is very interesting. This level of cache is available for the whole of application and it will return the object or an object that already is/are loaded on the cache. Any transaction is definitely avoided.

DIFFERNET KIND OF CACHING PACKAGES We have at least 4 different caching packages: 1-EhCache: http://ehcache.sourceforge.net/ It is used widely in the J2EE and light-weight application Some advantages of EhCache are: 1-it is fast 2-easy to use 3- it has support all, memory or disc caching 4- it has support read-only, read/write caching But it hasn’t support clustering-cache system Page 6

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2- OsCache: http://www.opensymphony.com/oscache/ It is used to generate dynamically jsp-pages and it includes the jsp-library. You can use it in the large system. Some advantages: - It has support all, memory, disc and some basic support for clustering-cache system by using JMS, JavaGroup. - It has upport for read-only, read/write caching 3- SwarmCache: http://swarmcache.sourceforge.net/ It has simple support for clustering cache system. It has support for read-only, read/write caching It is very good to use this caching-method when you have many read operation than write operation.

4-Jboss TreeCache

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WHAT YOU SHOULD THINK FOR IMPLEMENTATE A CACHING SYSTEM

Caching planning:

As you can see there are different caching packages that you can use them on what you want to do We have at least 4 different caching plan: 1-read only; as you can guess this plan is good if you have just data that it doesn’t ever change. You can use Ehcache or OsCache 2- read/write: in this case the data needs to update, frequently. You can EhCache or OsCache 3-nonStrick read/write. It doesn’t guaranty that any update shouldn’t take place more than once. You can use SwarmCache 4-transactional caching plan. You can use this plan for JTA (Java transactional API). You can use Jobs treeCache

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EHCACHE EXAMPLE

I will here give two example of using eHcache. One in java main, the second with servlet.

To using Ehcache, you need a configuration file, which here I call it ehcache.xml. There you can define your caching policy as well as: maxElementsInMemory eternal timeToIdleSeconds timeToLiveSeconds and so on. The configuration file can look like this:

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And maybe you want to have a bean as follows. package martin.nad.cache.ehcache.exampel1; import java.io.Serializable; public class Customer implements Serializable { /** * */ private static final long serialVersionUID = 1L; private String name = ""; private String address = ""; public Customer () { // Default constructor. } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; }

public String getName() { return name;

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}

public void setName(String name) { this.name = name; }

And your main class:

package martin.nad.cache.ehcache.exampel1;

/** * */ 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.*;

public class App

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{ public static void main( String[] args ) { App app = new App();

try { app.manager = CacheManager.create("c:/tmp/enCache.xml"); System.out.println("manager is...."+app.manager); app.cache = app.manager.getCache("sampleCache1"); } catch (Exception e) { System.out.println(e); }

read_writeInCache();

}

public void destroy() { }

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protected void read_writeInCache() {

Customer mycustomer = new Customer (); mycustomer.setName("Martin Nad"); mycustomer.setAddress("my address");

// Caching this element Element element = new Element(mycustomer.getName(), mycustomer); System.out.println("element is: "+element); System.out.println(this.cache); cache.put(element);

// Reading the cache try { element = cache.get("Martin Nad"); } catch (Exception e) {}

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Customer my2customer = (Customer)element.getValue();

System.out.println("Cache loaded "); System.out.println("Name : " + my2customer.getName() ); System.out.println("address : " + my2customer.getAddress() ); } private CacheManager manager = null; private Cache cache = null;

}

And just run, and you are done with your first cachingsystem.

If you want use in your servlet, your servlet can look like:

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package martin.nad.cache.ehcache.exampel1;

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.*;

public class servletEhcacheExample1 extends HttpServlet {

private static Logger logger = Logger.getLogger(servletEhcacheExample1.class.getName());

private CacheManager manager = null;

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private Cache cache = null;

public void init() throws ServletException {

PropertyConfigurator.configure( getServletContext().getRealP ath ("WEB-INF/log4j.properties") );

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() {}

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protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { doGet(req, res); }

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

PrintWriter out = response.getWriter();

Customer myCustomer = new Customer (); myCustomer.setName("Martin Nad"); myCustomer.setAddress("some address");

Element element = new Element(myCustomer.getName(), myCustomer); cache.put(element);

// Reading the cache try {

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element = cache.get("Martin Nad"); } catch (Exception e) {}

Customer myNewCustomer = (Customer)element.getValue();

out.println("Name : " + myNewCustomer.getName() +""); out.println("Address : " + myNewCustomer.getAddress() +""); } }

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OPEN SYMPHONY CACHING OSCACHE DONATION If you like this documentation and it was helpful you can just donate 7$ by using this https://www.paypal.com/cgi-bin/webscr?cmd=_s-

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