Servlet中如何获得ApplicationContext , Spring

applicationContext.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:aop="http://www.springframework.org/schema/aop"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xsi:schemaLocation="
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
       http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd
       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd"
	default-lazy-init="false">

	<!-- data source -->

	<bean id="dataSource"
		class="org.springframework.jndi.JndiObjectFactoryBean">
		<property name="jndiName"
			value="java:comp/env/jdbc/MyTestProject" />
	</bean>


	<!-- 配置数据源 供测试用-->
	<bean id="dataSourceDebug"
		class="org.springframework.jdbc.datasource.DriverManagerDataSource">
		<property name="driverClassName"
			value="com.microsoft.sqlserver.jdbc.SQLServerDriver">
		</property>
		<property name="url"
			value="jdbc:sqlserver://192.168.0.1\SQLEXPRESS:1433;dataBaseName=Test;loginTimeout=3;">
		</property>
		<property name="username" value="sa"></property>
		<property name="password" value="123"></property>
	</bean>

	<bean id="abstractDao" abstract="true">
		<!-- 
			<property name="dataSource" ref="dataSourceDebug"></property>
		-->
		<property name="dataSource" ref="dataSource"></property>
	</bean>

	<bean id="firstDao" class="com.wcg.FirstDaoImpl"
		parent="abstractDao">
	</bean>

</beans>

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

	<!--  Spring context loader -->
	<listener>
		<listener-class>
			org.springframework.web.context.ContextLoaderListener
		</listener-class>
	</listener>
	<servlet>
		<description>测试FirstDao</description>
		<display-name>FirstServlet</display-name>
		<servlet-name>FirstServlet</servlet-name>
		<servlet-class>com.servlet.FirstServlet</servlet-class>
	</servlet>

	<servlet-mapping>
		<servlet-name>FirstServlet</servlet-name>
		<url-pattern>/servlet/FirstServlet</url-pattern>
	</servlet-mapping>

	<!-- jdbc resource -->
	<resource-ref>
		<res-ref-name>jdbc/MyTestProject</res-ref-name>
		<res-type>javax.sql.DataSource</res-type>
		<res-auth>Container</res-auth>
	</resource-ref>

</web-app>

//FirstDao.java

package com.wcg;

public interface FirstDao {

	public int Create(String name);
	
}

//FirstDaoImpl.java
package com.wcg;

import java.util.HashMap;
import java.util.Map;

import org.springframework.jdbc.core.simple.SimpleJdbcDaoSupport;

public class FirstDaoImpl extends SimpleJdbcDaoSupport implements FirstDao {

	public int Create(String name) {
		String sql = "insert into T (Name) values(:Name)";
		Map<String, Object> param = new HashMap<String, Object>();
		param.put("Name", name);
		return this.getSimpleJdbcTemplate().update(sql, param);
	}

}

//FirstServlet.java
//...

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

		response.setContentType("text/html");
		PrintWriter out = response.getWriter();

		ServletContext sc = request.getSession().getServletContext();
		WebApplicationContext ctx = (WebApplicationContext)sc.getAttribute("org.springframework.web.context.WebApplicationContext.ROOT");
		String name = request.getParameter("name");
		FirstDao fd = (FirstDao) ctx.getBean("firstDao");
		fd.Create(name);

		out.println("Done");
		out.flush();
		out.close();
	}
//...

测试,web容器之外的测试类.
//Test.java
package com.wcg;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;

public class Test {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		//ApplicationContext ctx = new ClassPathXmlApplicationContext("..\\applicationContext.xml");
		ApplicationContext ctx = new FileSystemXmlApplicationContext("D:\\proj_ja\\java\\TestWeb\\WebRoot\\WEB-INF\\applicationContext.xml");
		
		
		FirstDao fd = (FirstDao) ctx.getBean("firstDao");
		fd.Create("username");

		System.out.println("done");
	}

}