文章目录
1. Spring与Web环境集成
1.1 ApplicationContext应用上下文获取方式
应用上下文对象是通过new ClasspathXmlApplicationContext
(spring配置文件) 方式获取的,但是每次从容器中获得Bean时都要编写new ClasspathXmlApplicationContext
(spring配置文件) ,这样的弊端是配置文件加载多次,应用上下文对象创建多次。
在Web项目中,可以使用ServletContextListener
监听Web应用的启动,我们可以在Web应用启动时,就加载Spring的配置文件,创建应用上下文对象ApplicationContext,在将其存储到最大的域servletContext域中,这样就可以在任意位置从域中获得应用上下文ApplicationContext对象了。
package com.jacksun.dao.impl;
import com.jacksun.dao.UserDao;
public class UserDaoImpl implements UserDao {
public void save() {
System.out.println("dao-------------");
}
}
package com.jacksun.service.impl;
import com.jacksun.dao.UserDao;
import com.jacksun.dao.impl.UserDaoImpl;
import com.jacksun.service.UserService;
public class UserServiceImpl implements UserService {
private UserDao userDao;
public void save(){
userDao.save();
}
//注入
public void setUserDao(UserDaoImpl userDao) {
this.userDao=userDao;
}
// public UserServiceImpl(UserDao userDao) {
// this.userDao = userDao;
// }
//
//
// public UserServiceImpl() {
//
// }
}
package com.jacksun.web;
import com.jacksun.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
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 java.io.IOException;
@WebServlet("/userServlet")
public class UserServlet extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
UserService userService = app.getBean(UserService.class);
userService.save();
}
}
<?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="userDao" class="com.jacksun.dao.impl.UserDaoImpl"></bean>
<bean id="userService" class="com.jacksun.service.impl.UserServiceImpl">
<property name="userDao" ref="userDao"/>
</bean>
</beans>
1.2 Spring提供获取应用上下文的工具
上面的分析不用手动实现,Spring提供了一个监听器ContextLoaderListener就是对上述功能的封装,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。
所以我们需要做的只有两件事:
①在web.xml中配置ContextLoaderListener监听器(导入spring-web坐标)
②使用WebApplicationContextUtils获得应用上下文对象ApplicationContext
1.3 导入Spring集成web的坐标
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>5.0.5.RELEASE</version>
</dependency>
1.4 配置ContextLoaderListener监听器
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
public class ContextLoaderListener implements ServletContextListener {
public void contextInitialized(ServletContextEvent servletContextEvent) {
ServletContext servletContext = servletContextEvent.getServletContext();
//读取web.xml中的全局参数
String contextConfigLocation = servletContext.getInitParameter("contextConfigLocation");
ApplicationContext app = new ClassPathXmlApplicationContext(contextConfigLocation);
//将Spring的应用上下文对象存储到ServletContext域中
servletContext.setAttribute("app",app);
System.out.println("spring容器创建完毕....");
}
public void contextDestroyed(ServletContextEvent servletContextEvent) {
}
}
下面spring自动提供的
<!--全局参数-->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</context-param>
<!--Spring的监听器-->
<listener>
<listener-class>
org.springframework.web.context.ContextLoaderListener
</listener-class>
</listener>
1.5 通过工具获得应用上下文对象
//ApplicationContext applicationContext = WebApplicationContextUtils.getWebApplicationContext(servletContext);
//Object obj = applicationContext.getBean("id");
ServletContext servletContext = this.getServletContext();
ServletContext .setAttribute("app",app)
知识要点
Spring集成web环境步骤
①配置ContextLoaderListener监听器
②使用WebApplicationContextUtils获得应用上下文