5 minutes with - Spring Cache

Many times happens that we read information that we’ve already read just few time ago. These could be database, fileSystem or rss feed independently.

For the very static contexts (as weather forecast services) that changes once a day, calling the resource every time we need to show, it’s a very waste of time for our application.

For solve this problems, the keyword is cache. Now, I show you how implementing ehcache system with spring.

First, the official ehcache web site http://ehcache.org/

In this demo I used a Spring MVC web application and one simple Bean. it has a cached method. In the same Bean I wrote a method to evict the cache.

My libraries

aopalliance-1.0.jar
asm-3.0.jar
aspectjweaver-1.6.6.jar
cglib-2.2.jar
commons-logging-1.1.1.jar
ehcache-1.6.2.jar
jstl-1.2.jar
junit-4.8.1.jar
lib.txt
log4j-1.2.14.jar
spring-aop-3.1.0.RELEASE.jar
spring-asm-3.1.0.RELEASE.jar
spring-beans-3.1.0.RELEASE.jar
spring-context-3.1.0.RELEASE.jar
spring-core-3.1.0.RELEASE.jar
spring-expression-3.1.0.RELEASE.jar
spring-test-3.1.0.RELEASE.jar
spring-web-3.1.0.RELEASE.jar
spring-webmvc-3.1.0.RELEASE.jar
standard-1.1.2.jar

In the web.xml is defined the spring servlet definition.

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi=<a href="http://www.w3.org/2001/XMLSchema-instance">http://www.w3.org/2001/XMLSchema-instance</a>
 xmlns="http://java.sun.com/xml/ns/javaee"
 xmlns:web=<a href="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd</a>
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
 id="WebApp_ID" version="2.5">
 <display-name>Spring3MVC</display-name>
 <welcome-file-list>
  <welcome-file>index.jsp</welcome-file>
 </welcome-file-list>

 <servlet>
  <servlet-name>spring</servlet-name>
  <servlet-class>
   org.springframework.web.servlet.DispatcherServlet
  </servlet-class>
  <load-on-startup>1</load-on-startup>
 </servlet>
 <servlet-mapping>
  <servlet-name>spring</servlet-name>
  <url-pattern>*.html</url-pattern>
 </servlet-mapping>
</web-app>
<pre>

The spring-servlet.xml file include the cache manager bean and speaker bean who will be used for calling the cached methods.

<bean id="cacheManager" class="org.springframework.cache.ehcache.EhCacheCacheManager"
		p:cache-manager-ref="ehcache" />
	<bean id="ehcache"
		class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean"
		p:config-location="classpath:ehcache.xml" />

	<bean id="Speaker" class="it.sample.springcache.bean.Speaker" />

In ehcache.xml file I configured the speakerCache cache type.

<?xml version="1.0" encoding="UTF-8"?>
<ehcache>

	<defaultCache
                maxElementsInMemory="50"
                eternal="false"
                overflowToDisk="false"
                memoryStoreEvictionPolicy="LFU" />

        <cache name="persons"
                maxElementsInMemory="50"
                eternal="false"
                overflowToDisk="false"
                memoryStoreEvictionPolicy="LFU" />

		<cache name="wordCache" eternal="false" maxElementsInMemory="100"
			overflowToDisk="false" diskPersistent="false"
			timeToIdleSeconds="0" timeToLiveSeconds="60" memoryStoreEvictionPolicy="LRU" />

</ehcache>

All arguments are explained in this link http://ehcache.org/apidocs/net/sf/ehcache/config/CacheConfiguration.html

In few words I configured a cache with max 100 elements in memory and with expiry time of 60 seconds.

Take a look at Speaker class. There are two methods inside: sayWord and clearWord and each of them accept one “word” parameter.

The annotations @Cacheable and @CacheEvict mean “put in cache” and “evict from cache” with the key parameter “word”.

package it.sample.springcache.bean;
import org.springframework.cache.annotation.CacheEvict;
import org.springframework.cache.annotation.Cacheable;
public class Speaker {
 @Cacheable(value="wordCache", key="#word")
 public String sayWord(String word)
 {
  return word;
 }
 
 @CacheEvict(value="wordCache", key="#word")
 public String clearWord(String word)
 {
  return "Ok";
 }
}

The last class is the controller MVC with the annotation for Url /speaker and /speakerclear

package it.sample.springcache.controller;
import it.sample.springcache.bean.Speaker;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;
@Controller
public class HelloWorldController {
 @Autowired
 Speaker speaker;
 
 @RequestMapping("/speaker")
 public ModelAndView speakerWorld(@RequestParam(required=true) String message) {
  message = speaker.sayWord(message);
  System.out.println(message);
  return new ModelAndView("speaker", "message", message);
 }
 
 @RequestMapping("/speakerclear")
 public ModelAndView speakerWorldClear(@RequestParam(required=true) String message) {
  message = speaker.clearWord(message);
  System.out.println(message);
  return new ModelAndView("speaker", "message", message);
 }
}

It’s time to launch Tomcat and browse the url /hello.html?message=hello. If you call again the same url you can check that the method sayWord(“hello”) has been cached. You can call /helloclear.html?message=hello or wait for 60 seconds to evict the value from the cache.

Update

The source code is available at this link  SpringCache (Please, substitute the .doc extension with .zip extension)

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