Java web项目创建笔记3 之《springmvc基础配置—xml配置文件》

1、springmvc配置应用上下文有两种方式：
1）第一种是配置一个Servlet WebApplicationContext和Root WebApplicationContext
Servlet WebApplicationContext是springmvc使用
Root WebApplicationContext是全局配置，比如：事务管理、数据源

2）第二种是配置Root WebApplicationContext对单个DispatcherServlet

2、配置web.xml
这里使用第一种配置方法

<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_3_1.xsd"
	     version="3.1">
	<display-name>Archetype Created Web Application</display-name>

	<!--配置spring前端控制器 -->
	<servlet>
		<servlet-name>dispatcherServlet</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<init-param>
			<param-name>contextConfigLocation</param-name>
			<param-value>classpath:spring-mvc.xml</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
	</servlet>

	<servlet-mapping>
		<servlet-name>dispatcherServlet</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>

	<!-- 配置初始化root WebApplicationContext -->
	<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>

	<!-- 字符编码过滤器 统一编码UTF-8 -->
	<filter>
		<filter-name>encodingFilter</filter-name>
		<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
		<init-param>
			<param-name>encoding</param-name>
			<param-value>UTF-8</param-value>
		</init-param>
	</filter>

	<filter-mapping>
		<filter-name>encodingFilter</filter-name>
		<url-pattern>/*</url-pattern>
		<dispatcher>REQUEST</dispatcher>
		<dispatcher>FORWARD</dispatcher>
	</filter-mapping>
	
</web-app>

3、web.xml解析过程
1）web项目启动，容器（tomcat）创建ServletContext————由tomcat代码实现
2）容器开始读取web.xml文件
3）读取<context-param></context-param>作为键值对存到ServletContext中
4）触发ServletContextEvent事件
spring的ContextLoaderListener监听器继承ContextLoader类，实现ServletContextListener接口
ServletContextListener接口监听ServletContextEvent事件

public class ContextLoaderListener extends ContextLoader implements ServletContextListener {
​​​​​​​    ...
}

5）ContextLoaderListener执行初始化方法
创建root WebApplicationContext，并以键值对放入ServletContext中
6）web.xml的加载顺序是：context-param -> listener -> filter -> servlet ，而同个类型之间的实际程序启动的顺序是根据对应的mapping定义的顺序进行启动的

4、配置spring-mvc.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"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-4.1.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd">

	<!-- 基于注解的自动装配 -->
	<context:annotation-config />

	<!-- 只扫描Controller -->
	<context:component-scan base-package="com.study.resources">
		<context:include-filter type="annotation"
			expression="org.springframework.stereotype.Controller" />
	</context:component-scan>

	<!-- 开启注解驱动 -->
	<mvc:annotation-driven />

	<!-- 使用默认的Servlet来响应静态文件 -->
	<mvc:default-servlet-handler />

	<!-- 配置视图解析器 -->
	<bean
		class="org.springframework.web.servlet.view.InternalResourceViewResolver"
		id="internalResourceViewResolver">
		<!-- 前缀 -->
		<property name="prefix" value="/WEB-INF/jsp/" />
		<!-- 后缀 -->
		<property name="suffix" value=".jsp" />
	</bean>

</beans>

5、spring-mvc.xml说明
1）<context:annotation-config />
打开自动装配
2）<context:component-scan></context:component-scan>
打开自动扫描，此处只扫描Controller注解
3）<mvc:annotation-driven />
开启mvc的注解驱动，自动注册默认处理请求，参数和返回值的类
4）<mvc:default-servlet-handler />
静态页面，如html、css、js、images可以访问

6、配置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"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-4.1.xsd">

	<!-- 注解bean扫描,spring扫描排除Controller -->
	<context:annotation-config />
	<context:component-scan base-package="com.study">
		<context:exclude-filter type="annotation"
			expression="org.springframework.stereotype.Controller" />
	</context:component-scan>

	<!-- 下面可以导入其他spring配置文件 -->

</beans>

7、在src下建立测试controller

package com.study.resources;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
@RequestMapping("mvc")
public class TestController {

	@RequestMapping("hello")
	private String hello() {
		return "hello";
	}
}

8、在WEB-INF下新建jsp文件夹，新建hello.jsp文件

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    Hello!
</body>
</html>

9、启动tomcat，访问测试页面：http://127.0.0.1:8080/webapp/mvc/hello

10、其他注意事项

<servlet-mapping>
		<servlet-name>dispatcherServlet</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>

 这段url-pattern如果写成 /* 会拦截jsp页面，导致浏览器不能正确解析jsp页面，直接显示源代码

参考资料：
1）总结下ServletContext和ApplicationContext
http://www.noobyard.com/article/p-kluufaop-ud.html

2）web.xml 中的listener、 filter、servlet 加载顺序及其详解
http://www.noobyard.com/article/p-ejbbhopd-e.html