如何在Spring中池对象？

编程入门行业动态更新时间:2024-10-11 13:25:30

本文介绍了如何在Spring中池对象？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！问题描述

我正在关注教程关于如何在Spring中池对象。我按照教程中的说明进行操作，但是当我运行我的应用程序时，它总是会生成一个新的对象实例。我期待，因为我正在汇集对象，现有的对象将被重用。因此，不应创建新实例。此外，当我访问bean的getter方法时，会再次创建bean的新实例。

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.

我可能做错了什么？我是否误解了Spring中汇集的概念？

What could have I done wrong? Did I misunderstood the concept of pooling in Spring?

以下是我的代码：

应用程序上下文：（这只是我的应用程序上下文的主体。）

Application Context: (This is just the body of my application context.)

控制器：（这只是我方法的主体）

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()); } }

我正在汇集的bean：

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; } }

我的web.xml正文：

<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>

推荐答案

在每个请求中，您创建一个全新的Spring应用程序上下文，然后在每个动作的新应用程序上下文中获取新对象。所以你应该在web.xml中加载你的spring上下文使用'ContextLoaderListener'。

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.

web.xml中的参考片段

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>

查看代码：

try { System.out.println("Accessing Application Context"); ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); ...

有关Spring上下文加载的更多知识，请参阅 MKyong的教程或 Spring reference

For more knowledge about Spring context loading, see MKyong 's tutorial or Spring reference