Spring -- 集成web环境

1. 集成web环境

准备工作：

开始之前先进行基础环境搭建

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1.1 ApplicationContext应用 上下文获取方式

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1.1.1 创建监听器

ContextLoaderListener.java

package com.tian.listener;


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

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

public class ContextLoaderListener implements ServletContextListener {

    
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        //将Spring的应用上下文对象存储到ServletContext域中
        servletContextEvent.getServletContext().setAttribute("context", context);
        System.out.println("spring容器创建完毕....");
    }

    public void contextDestroyed(ServletContextEvent servletContextEvent) {

    }
}

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1.1.2 配置监听器

web.xml

    
        UserServlet
        com.tian.web.UserServlet
    
    
        UserServlet
        /userServlet
    

    
    
        com.tian.listener.ContextLoaderListener
    

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1.1.3 重新get请求 更换获取Spring上下文的方式

之前的方式：

现在的方式：从servletContext域中获取context

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
        ServletContext servletContext = this.getServletContext();
        ApplicationContext context = (ApplicationContext) servletContext.getAttribute("context");
        UserServiceImpl bean = context.getBean(UserServiceImpl.class);
        bean.save();
    }

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1.1.4 启动服务器测试

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1.2 Spring提供获取应用上下文的工具

Spring提供了一个监听器ContextLoaderListener，该监听器内部加载Spring配置文件，创建应用上下文对象，并存储到ServletContext域中，提供了一个客户端工具WebApplicationContextUtils供使用者获得应用上下文对象。（可以把我们之前创建的监听器删了，现在用Spring提供的监听器）

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1.2.1 导入Spring集成web的坐标

        
            org.springframework
            spring-web
            5.3.7
        

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1.2.2 配置ContextLoaderListener监听器

web.xml

    
        UserServlet
        com.tian.web.UserServlet
    
    
        UserServlet
        /userServlet
    

    
    
        contextConfigLocation
        classpath:applicationContext.xml
    
    
    
        org.springframework.web.context.ContextLoaderListener
    

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1.2.3 开始测试

现在的UserServlet代码：

package com.tian.web;


import com.tian.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class UserServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        //        获取ApplicationContext
        ServletContext servletContext = this.getServletContext();
        //        获取Spring Ioc容器的上下文
        ApplicationContext context = WebApplicationContextUtils.getWebApplicationContext(servletContext);
        //        从Ioc容器获取bean
        UserService userService = context.getBean(UserService.class);
        // 调用bean的方法
        userService.save();
    }
}

启动服务器:

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