我正在关注如何在
Spring中汇集对象的这个
tutorial.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.
我怎么可能做错了？我是否误解了Spring中汇集的概念？
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.)
<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>
控制器:(这只是我方法的主体)
@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","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的正文：
<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>
解决方法
在每个请求中,您创建一个全新的Spring应用程序上下文,然后在每个操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’.
web.xml中的引用片段
<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>
看你的代码：
try
{
System.out.println("Accessing Application Context");
ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
...
有关Spring上下文加载的更多信息,请参阅MKyong ‘s tutorial或Spring reference
