在web应用中使用spring的基本思路

1、在pom.xml文件中必须加入如下配置

<dependency>
     <groupId>org.springframework</groupId>
     <artifactId>spring-web</artifactId>
     <version>${spring.version}</version>
</dependency>
<dependency>
     <groupId>org.springframework</groupId>
     <artifactId>spring-webmvc</artifactId>
     <version>${spring.version}</version>
</dependency>

2、WEB应用下Spring的配置文件和非WEB应用下没有不同

3、如何创建IOC容器

• 非web应用在main方法中直接创建
• 应该在WEB应用被服务器加载时就创建IOC容器：在ServletContextListener#contextInitialized(ServletContextEvent sce)方法中创建IOC容器
• 在web应用的其他组件中如何访问IOC容器：在ServletContextListener#contextInitialized(ServletContextEvent sce)方法中创建IOC容器后，可以把其放在ServletContext(即application域)的一个属性中
• 实际上，spring配置文件的名字和位置也是可配置的，将其配置到当前web应用的初始化参数中（web.xml）

下面具体介绍实例：

1)首先新建Person类

package com.wn.beans;

public class Person {
    private String username;

    public void setUsername(String username) {
        this.username = username;
    }

    public void hello() {
        System.out.println("my name is：" + username);
    }
}

2)spring配置文件与非web情况下一样

<?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:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
                           http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
                           http://www.springframework.org/schema/context 
                           http://www.springframework.org/schema/context/spring-context-3.2.xsd
                           http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd">
    <bean id="person" class="com.wn.beans.Person">
        <property name="username" value="atguigu"></property>
    </bean>
</beans>

 

3）创建SpringServletContextListener类使用ServletContextListener的监听器功能，在ServletContextListener#contextInitialized(ServletContextEvent sce)方法

    中创建IOC容器，然后将IOC容器放在ServletContext的一个属性中

package com.wn.listener;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
/**
 * Application Lifecycle Listener implementation class
 * SpringServletContextListener
 */
public class SpringServletContextListener implements ServletContextListener {
    /**
     * Default constructor.
     */
    public SpringServletContextListener() {
        // TODO Auto-generated constructor stub
    }
    /**
     * @see ServletContextListener#contextDestroyed(ServletContextEvent)
     */
    public void contextDestroyed(ServletContextEvent arg0) {
        // TODO Auto-generated method stub
    }
    /**
     * @see ServletContextListener#contextInitialized(ServletContextEvent)
     */
    public void contextInitialized(ServletContextEvent arg0) {
        // 1、获取spring配置文件的名称和位置
        ServletContext servletContext=arg0.getServletContext();
        /**1、getInitParameter()方法是在GenericServlet接口中新定义的一个方法，用来调用初始化在web.xml中存放的参量。
        如果通过在web.xml中的ServletContext上下文中定义参量，那么整个web应用程序中的servlet都可调用，web.xml中的格式为：
         <context-param>
                <param-name>test</param-name>
                <param-value>Is it me</param-value>
         < context -param>
           2、调用<context-param>中的参量,调用格式为：
        String name =getServletContext(). getInitParameter(“name”); 或
        String name = getServletConfig().getServletContext().getInitParameter(“name”);
         */
        String config=servletContext.getInitParameter("configLocation");
        // 2、创建IOC容器
        ApplicationContext ctx = new ClassPathXmlApplicationContext(config);
        // 3、将IOC容器放在ServletContext的一个属性中
        servletContext.setAttribute("ApplicationContext",ctx);
    }
}

4）在web.xml文件中配置如下信息

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    version="2.5">
    <!-- 配置spring配置文件的名称和位置 -->
    <context-param>
        <param-name>configLocation</param-name>
        <param-value>applicationContext2.xml</param-value>
    </context-param>
    <!-- 启动IOC容器的ServletContextListener -->
    <listener>
        <listener-class>com.wn.listener.SpringServletContextListener</listener-class>
    </listener>
    <!-- 配置服务器运行路径 -->
    <servlet>
        <servlet-name>testServlet</servlet-name>
        <servlet-class>com.wn.servlet.TestServlet</servlet-class>
        <init-param>
            <param-name>configLocation</param-name>
            <param-value>classpath*:applicationContext2*.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>testServlet</servlet-name>
        <url-pattern>/TestServlet</url-pattern>
    </servlet-mapping>
</web-app>

5）创建TestServlet类

package com.wn.servlet;

import java.io.IOException;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.context.ApplicationContext;

import com.wn.beans.Person;

/**
 * Servlet implementation class TestServlet
 */
//@WebServlet("/TestServlet")
public class TestServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
     *      response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // 从application域对象中得到IOC容器的引用
        ServletContext servletContext = getServletContext();
        ApplicationContext ctx = (ApplicationContext) servletContext.getAttribute("ApplicationContext");
        // 从IOC容器中得到需要的bean
        Person person = ctx.getBean(Person.class);
        person.hello();
        response.getWriter().append("Served at: ").append(request.getContextPath());
    }
}

6）创建index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <a href="TestServlet">TestServlet</a>
</body>
</html>

在浏览器中输入http://localhost:8080/second-ssmm/TestServlet，在console中打印出：

         my name is：atguigu

说明：配置浏览器路径可以通过上述在web.xml文件中配置，加上6）index.jsp运行，也可以去掉6）index.jsp和web中相关Servlet的配置，直接在5）中TestServlet类

        中第19行代码那样加注解@WebServlet("/TestServlet")