Spring development web project
Because there is the only entry main() function in java, the IOC container can be initialized directly in the java program:
//初始化spring容器，加载配置文件
ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
There is no unified entry point for web programs. It is a waste of performance to initialize IOC every time it is used. So, how to simplify it?
Idea: Through the listener, we initialize the IOC container every time we start the server.
Spring development web project:
Everyone you can think of has thought of it, just call the method given by the predecessors directly.
Download Spring-web.jar : https://mvnrepository.com/artifact/org.springframework/spring-web/5.1.3.RELEASE
web.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<!--指定IOC容器，contextConfigLocation名固定-->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</context-param>
<listener>
<!--配置监听器，初始化IOC容器-->
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
</web-app>
Create a new applicationContext.xml file in the src directory. applicationContext.xml is the IOC container.
Split web configuration file
1. Split according to function 2. Split
according to three-layer structure
Easy to split , how to merge?
The bridge between servlet container and IOC
//获取IOC容器到servlet容器
@Override
public void init() throws ServletException {
ApplicationContext context = WebApplicationContextUtils.getWebApplicationContext(this.getServletContext());
context.getbean("对象");
}