Spring与web

1. Spring 如何在 WEB 应用中使用 ?

1). 需要额外加入的 jar 包:

spring-web-4.0.0.RELEASE.jar
spring-webmvc-4.0.0.RELEASE.jar

2). Spring 的配置文件, 没有什么不同

3). 如何创建 IOC 容器 ?

①. 非 WEB 应用在 main 方法中直接创建
②. 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. 监听器

③. 在 WEB 应用的其他组件中如何来访问 IOC 容器呢 ?

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.

④. 实际上, Spring 配置文件的名字和位置应该也是可配置的! 将其配置到当前 WEB 应用的初始化参数中较为合适.

监听器：

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package com.atguigu.spring.struts2.listeners;

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#contextInitialized(ServletContextEvent)
     */
    public void contextInitialized(ServletContextEvent arg0) {
        //1. 获取 Spring 配置文件的名称. 
        ServletContext servletContext = arg0.getServletContext();
        String config = servletContext.getInitParameter("configLocation"); // "configLocation"配置文件中的别名
        
        //1. 创建 IOC 容器
        ApplicationContext ctx = new ClassPathXmlApplicationContext(config);
        
        //2. 把 IOC容器放在 ServletContext 的一个属性中. 
        servletContext.setAttribute("ApplicationContext", ctx);
    }

    /**
     * @see ServletContextListener#contextDestroyed(ServletContextEvent)
     */
    public void contextDestroyed(ServletContextEvent arg0) {
        // TODO Auto-generated method stub
    }
    
}

搞一个servlet 然后从中得到 IOC容器获取容器中的bean

package com.atguigu.spring.struts2.servlets;

import java.io.IOException;

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

import org.springframework.context.ApplicationContext;

import com.atguigu.spring.struts2.beans.Person;

/**
 * Servlet implementation class 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 {
        //1. 从 application 域对象中得到 IOC 容器的引用
        ServletContext servletContext = getServletContext();
        ApplicationContext ctx = (ApplicationContext) servletContext.getAttribute("ApplicationContext");
        
        //2. 从 IOC 容器中得到需要的 bean
        Person person = ctx.getBean(Person.class);
        person.hello();
    }

}

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

Spring：

bean：

package com.atguigu.spring.struts2.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);
    }
    
}

service：

package com.atguigu.spring.struts2.services;

public class PersonService {
    
    public void save(){
        System.out.println("PersonService's save....");
    }
    
}

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"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="person" 
        class="com.atguigu.spring.struts2.beans.Person">
        <property name="username" value="spring"></property>    
    </bean>
    
    <bean id="personService"
        class="com.atguigu.spring.struts2.services.PersonService"></bean>
    
    <!-- 注意: 在 IOC 容器中配置 Struts2 的 Action 时, 需要配置 scope 属性, 其值必须为 prototype -->
    <bean id="personAction" 
        class="com.atguigu.spring.struts2.actions.PersonAction"
        scope="prototype">
        <property name="personService" ref="personService"></property>    
    </bean>
    
</beans>

jsp：

<%@page import="com.atguigu.spring.struts2.beans.Person"%>
<%@page import="org.springframework.web.context.support.WebApplicationContextUtils"%>
<%@page import="org.springframework.context.ApplicationContext"%>
<%@ 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>
    
    <% 
        //1. 从 appication 域对象中得到 IOC 容器的实例
        ApplicationContext ctx = WebApplicationContextUtils.getWebApplicationContext(application);
         
        //2. 从 IOC 容器中得到 bean
        Person person = ctx.getBean(Person.class);
        
        //3. 使用 bean
        person.hello();
    %>
    
</body>
</html>

web.xml

<?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" id="WebApp_ID" version="2.5">

    <!-- 配置 Spring 配置文件的名称和位置 -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
    
    <!-- 启动 IOC 容器的 ServletContextListener -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    

</web-app>

启动时候会打印 hello的内容

总结：

在 WEB 环境下使用 Spring

①. 需要额外加入的 jar 包:

spring-web-4.0.0.RELEASE.jar
spring-webmvc-4.0.0.RELEASE.jar

②. Spring 的配置文件, 和非 WEB 环境没有什么不同

③. 需要在 web.xml 文件中加入如下配置:

<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</context-param>

<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

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