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  • spring之如何在web应用中使用?

    1.需要引入额外的jar包:

    • spring-web
    • spring-webmvc

    2.spring的配置文件没什么区别。

    3.如何创建IOC容器?

    • 非web应用在main方法中直接创建;
    • 在web应用中应该在被服务器加载时就创建;
    • 在ServletContextListener#contextInitialized(ServletContextEvent sce)方法中创建IOC容器;

    4.在WEB应用中其它组件如何来访问IOC容器呢?

    可以将IOC容器放在ServletContext(即applicaiton域)的一个属性中。

    5.实际上spring配置文件的名字和位置也是可以配置的。将其配置到当前web应用的初始化参数中较为合适。

    实际操作:

    新建一个动态的java web项目

    需要注意的是不要直接按finish,要一直到最后将web.xml文件导入进来。

    将相关的java包放入到WEB-INF的lib下。

    相关目录如下:

    Person.java

    package com.gong.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);
        }
        
    }

    SpringServletContextListener.java

    package com.gong.spring.struts2.listeners;
    
    import javax.servlet.ServletContext;
    import javax.servlet.ServletContextEvent;
    import javax.servlet.ServletContextListener;
    import javax.servlet.annotation.WebListener;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    /**
     * Application Lifecycle Listener implementation class SpringServletContextListener
     *
     */
    @WebListener
    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)  { 
            // TODO Auto-generated method stub
            //1.获取spring配置文件的名称
            ServletContext servletContext = arg0.getServletContext();
            String config = servletContext.getInitParameter("contextConfigLocation");
            //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);
        }
        
    }

    TestServlet.java

    package com.gong.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.gong.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();
        }
    
    }

    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.gong.spring.struts2.beans.Person">
            <property name="username" value="gong"></property>
        </bean>
    </beans>

    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" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
        id="WebApp_ID" version="3.0">
        <display-name>ssm</display-name>
    
        <!-- 加载springIOC容器 -->
        <context-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>applicationContext.xml</param-value>
        </context-param>
        <!-- 启动IOC容器的ServletContextListener -->
        <listener>
            <listener-class>com.gong.spring.struts2.listeners.SpringServletContextListener</listener-class>
        </listener>
        <servlet>
            <description></description>
            <display-name>TestServlet</display-name>
            <servlet-name>TestServlet</servlet-name>
            <servlet-class>com.gong.spring.struts2.servlets.TestServlet</servlet-class>
        </servlet>
        <servlet-mapping>
            <servlet-name>TestServlet</servlet-name>
            <url-pattern>/TestServlet</url-pattern>
        </servlet-mapping>
        <welcome-file-list>
            <welcome-file>index.jsp</welcome-file>
        </welcome-file-list>
    </web-app>

    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>

    启动tomcat服务器之后,访问http://localhost:8080/myspring5/index.jsp

    点击:

    在终端输出:

    说明在WEB应用中配置和使用springIOC容器是成功的。 

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  • 原文地址:https://www.cnblogs.com/xiximayou/p/12172667.html
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