How to pool objects in Spring?
On each request, you create a brand new Spring application context, then you get new object in a new applicatin context each action. so you should load your spring context use 'ContextLoaderListener' in web.xml.
Reference fragment in web.xml
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>
classpath*:spring/appContext.xml classpath*:spring/appContext-security.xml
</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
See you code:
try
{
System.out.println("Accessing Application Context");
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
...
For more knowledge about Spring context loading, see MKyong 's tutorial or Spring reference
Comments
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Arci almost 2 years
I'm following this tutorial regarding how to pool objects in Spring. I've followed the instruction written on the tutorial but when I run my application, it always generates a new instance of the object. I'm expecting that since I'm pooling the objects, existing objects will be reuse. As such, no new instances should be created. Also, when I access of the getter method of the bean, a new instance of the bean is created again.
What could have I done wrong? Did I misunderstood the concept of pooling in Spring?
Below is my code:
Application Context: (This is just the body of my application context.)
<bean id="simpleBeanTarget" class="com.bean.SimpleBean" scope="prototype"> </bean> <bean id="poolTargetSource" class="org.springframework.aop.target.CommonsPoolTargetSource"> <property name="targetBeanName" value="simpleBeanTarget" /> <property name="maxSize" value="2" /> </bean> <bean id="simpleBean" class="org.springframework.aop.framework.ProxyFactoryBean"> <property name="targetSource" ref="poolTargetSource" /> </bean>
The controller: (This is just the body of my method)
@RequestMapping("/hello") public ModelAndView helloWorld(HttpServletRequest request, HttpServletResponse response) { String message = "Hello World, Spring 3."; try { System.out.println("Accessing Application Context"); ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); System.out.println("Getting Bean"); SimpleBean simpleBean = (SimpleBean) context.getBean("simpleBean"); //A new SimpleBean... is printed here. System.out.println("Displaying Hello World: " + simpleBean.getRandomNum()); //After this line, A new SimpleBean... is printed again. I simply access the getter method. Why does it create a new instance of SimpleBean? return new ModelAndView("hello", "message", message); }catch(Exception e) { System.out.println("Error: " + e); e.printStackTrace(); return new ModelAndView("hello", "message", "Error! " + e.getMessage()); } }
The bean I'm pooling:
package com.bean; import java.util.Random; public class SimpleBean { int randomNum; String str; SimpleBean() { Random randomGenerator = new Random(); randomNum = randomGenerator.nextInt(100); //I'm printing this line just to check if a instance of this bean is created. System.out.println("#####################A new SimpleBean was born: " + randomNum); str = "This is a string."; } public int getRandomNum() { return randomNum; } public void setRandomNum(int randomNum) { this.randomNum = randomNum; } public String getStr() { if (str == null) return "str is null"; return str; } public void setStr(String str) { this.str = str; } }
The body of my web.xml:
<display-name>Spring3MVC</display-name> <context-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/classes/applicationContext.xml</param-value> </context-param> <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>