SpringMVC 学习笔记(一) Hello World

springMVC概述:

Spring MVC 是眼下最主流的MVC 框架之中的一个

Spring MVC 通过一套 MVC 注解。让 POJO 成为处理请

求的控制器，而无须实现不论什么接口。

支持 REST 风格的 URL 请求

採用了松散耦合可插拔组件结构，比其它 MVC 框架更具

扩展性和灵活性

项目结构图:

pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.ibigsea</groupId>
	<artifactId>springmvc</artifactId>
	<packaging>war</packaging>
	<version>0.0.1-SNAPSHOT</version>
	<name>springmvc</name>
	<url>http://maven.apache.org</url>
	<dependencies>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-core</artifactId>
			<version>${spring_version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-web</artifactId>
			<version>${spring_version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>${spring_version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
			<version>${spring_version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-aop</artifactId>
			<version>${spring_version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-beans</artifactId>
			<version>${spring_version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-expression</artifactId>
			<version>${spring_version}</version>
		</dependency>
		<dependency>
			<groupId>javax.servlet.jsp.jstl</groupId>
			<artifactId>jstl-api</artifactId>
			<version>1.2</version>
		</dependency>
		<dependency>
			<groupId>jstl</groupId>
			<artifactId>jstl</artifactId>
			<version>1.2</version>
		</dependency>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>3.8.1</version>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<spring_version>4.1.2.RELEASE</spring_version>
	</properties>

	<build>
		<finalName>springmvc</finalName>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>2.3.2</version>
				<configuration>
					<source>1.7</source>
					<target>1.7</target>
				</configuration>
			</plugin>
		</plugins>
	</build>

</project>

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"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
	version="3.0" >
	<!-- The front controller of this Spring Web application, responsible for handling all application requests -->
	<servlet>
		<servlet-name>springDispatcherServlet</servlet-name>
	<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!-- 载入spirng配置文件 -->
		<init-param>
			<param-name>contextConfigLocation</param-name>
			<param-value>classpath:spring-mvc.xml</param-value>
		</init-param>
        <!-- 启动就载入 -->
		<load-on-startup>1</load-on-startup>
	</servlet>

	<!-- 拦截全部请求 -->
	<servlet-mapping>
		<servlet-name>springDispatcherServlet</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>
</web-app>
	

通过在web.xml配置DispatcherServlet前端控制器, web容器 启动时载入,而且进行初始化.

由于HttpServlet继承了HttpServlet 所以在web容器启动运行时将会调用 init() 方法

当中initServletBean() 是HttpServletBean 提供给子类扩展的

FrameworkServlet 继承了 HttpServletBean 实现了initServletBean()这种方法,对web上下文进行初始化 . 而且提供了onRefresh(wac) 方法给子类实现   

DispatcherServlet继承了 FrameworkServlet 实现了onRefresh()这种方法

假设 web.xml中没有指定 contextConfigLocation . 则使用servlet-name 寻找xml文件.

 HelloWorld.java 

package com.ibigsea.springmvc.helloworld;

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

@Controller
public class HelloWorld {
	
	/**
	 * 配置@RequestMapping 拦截 localhost:8080/springmvc/hello 请求 
	 * @return
	 */
	@RequestMapping("/hello")
	public String helloWorld(){

		System.out.println("hello world");
		return "helloworld";
	}
}

 RequestMapping

详情请见第2章节

Spirng-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/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd
		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">
    <!-- 配置自己主动扫描包  扫描com.ibigsea.springmvc 包下的类 -->
	<context:component-scan base-package="com.ibigsea.springmvc"/>
<!-- 配置视图解析器 如返回helloworld     
                         为 [/WEB-INF/pages/helloworld.jsp] -->
	<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
     <!-- 前缀 -->
		<property name="prefix" value="/WEB-INF/pages/"/>
         <!-- 后缀 -->
		<property name="suffix" value=".jsp"/>
	</bean>
</beans>

当訪问 http://localhost:8080/springmvc/hello 后 DispatcherServlet 会拦截请求 

InternalResourceViewResolver 继承了 UrlBasedViewResolver 终于通过buildView() 解析

重定向和转发

普通情况下，控制器方法返回字符串类型的值会被当成逻辑视图名处理

• 假设返回的字符串中带 forward: 或 redirect: 前缀时，SpringMVC 会对他们进行特殊处理：将 forward: 和redirect: 当成指示符，其后的字符串作为 URL 来处理

– redirect:helloworld.jsp：会完毕一个到 helloworld.jsp 的重定向的操作

– forward:helloworld.jsp：会完毕一个到 helloworld.jsp 的转发操作

在 UrlBasedViewResolver 类里面的 createView 方法 解析