SpringMVC 学习笔记(一) Hello World

springMVC概述:

spring MVC 是目前最主流的MVC 框架之一

Spring MVC 通过一套 MVC 注解，让 POJO 成为处理请

求的控制器，而无须实现任何接口。

支持 REST 风格的 URL 请求

采用了松散耦合可插拔组件结构，比其他 MVC 框架更具

扩展性和灵活性

项目结构图:

pom.xml:

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1. <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
2.     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">  
3.     <modelVersion>4.0.0</modelVersion>  
4.     <groupId>com.ibigsea</groupId>  
5.     <artifactId>springmvc</artifactId>  
6.     <packaging>war</packaging>  
7.     <version>0.0.1-SNAPSHOT</version>  
8.     <name>springmvc</name>  
9.     <url>http://maven.apache.org</url>  
10.     <dependencies>  
11.         <dependency>  
12.             <groupId>org.springframework</groupId>  
13.             <artifactId>spring-core</artifactId>  
14.             <version>${spring_version}</version>  
15.         </dependency>  
16.         <dependency>  
17.             <groupId>org.springframework</groupId>  
18.             <artifactId>spring-web</artifactId>  
19.             <version>${spring_version}</version>  
20.         </dependency>  
21.         <dependency>  
22.             <groupId>org.springframework</groupId>  
23.             <artifactId>spring-webmvc</artifactId>  
24.             <version>${spring_version}</version>  
25.         </dependency>  
26.         <dependency>  
27.             <groupId>org.springframework</groupId>  
28.             <artifactId>spring-context</artifactId>  
29.             <version>${spring_version}</version>  
30.         </dependency>  
31.         <dependency>  
32.             <groupId>org.springframework</groupId>  
33.             <artifactId>spring-aop</artifactId>  
34.             <version>${spring_version}</version>  
35.         </dependency>  
36.         <dependency>  
37.             <groupId>org.springframework</groupId>  
38.             <artifactId>spring-beans</artifactId>  
39.             <version>${spring_version}</version>  
40.         </dependency>  
41.         <dependency>  
42.             <groupId>org.springframework</groupId>  
43.             <artifactId>spring-expression</artifactId>  
44.             <version>${spring_version}</version>  
45.         </dependency>  
46.         <dependency>  
47.             <groupId>javax.servlet.jsp.jstl</groupId>  
48.             <artifactId>jstl-api</artifactId>  
49.             <version>1.2</version>  
50.         </dependency>  
51.         <dependency>  
52.             <groupId>jstl</groupId>  
53.             <artifactId>jstl</artifactId>  
54.             <version>1.2</version>  
55.         </dependency>  
56.         <dependency>  
57.             <groupId>junit</groupId>  
58.             <artifactId>junit</artifactId>  
59.             <version>3.8.1</version>  
60.             <scope>test</scope>  
61.         </dependency>  
62.     </dependencies>  
63.   
64.     <properties>  
65.         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>  
66.         <spring_version>4.1.2.RELEASE</spring_version>  
67.     </properties>  
68.   
69.     <build>  
70.         <finalName>springmvc</finalName>  
71.         <plugins>  
72.             <plugin>  
73.                 <groupId>org.apache.maven.plugins</groupId>  
74.                 <artifactId>maven-compiler-plugin</artifactId>  
75.                 <version>2.3.2</version>  
76.                 <configuration>  
77.                     <source>1.7</source>  
78.                     <target>1.7</target>  
79.                 </configuration>  
80.             </plugin>  
81.         </plugins>  
82.     </build>  
83.   
84. </project>  

Web.xml:

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1. <?xml version="1.0" encoding="UTF-8"?>  
2. <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
3.     xmlns="http://java.sun.com/xml/ns/javaee"  
4.     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"  
5.     version="3.0" >  
6.     <!-- The front controller of this Spring Web application, responsible for handling all application requests -->  
7.     <servlet>  
8.         <servlet-name>springDispatcherServlet</servlet-name>  
9.     <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  
10.         <!-- 加载spirng配置文件 -->  
11.         <init-param>  
12.             <param-name>contextConfigLocation</param-name>  
13.             <param-value>classpath:spring-mvc.xml</param-value>  
14.         </init-param>  
15.         <!-- 启动就加载 -->  
16.         <load-on-startup>1</load-on-startup>  
17.     </servlet>  
18.   
19.     <!-- 拦截所有请求 -->  
20.     <servlet-mapping>  
21.         <servlet-name>springDispatcherServlet</servlet-name>  
22.         <url-pattern>/</url-pattern>  
23.     </servlet-mapping>  
24. </web-app>  
25.       

通过在web.xml配置DispatcherServlet前端控制器, web容器 启动时加载,并且进行初始化.

因为HttpServlet继承了HttpServlet 所以在web容器启动执行时将会调用 init() 方法

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

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

DispatcherServlet继承了 FrameworkServlet 实现了onRefresh()这个方法

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

 HelloWorld.java 

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1. package com.ibigsea.springmvc.helloworld;  
2.   
3. import org.springframework.stereotype.Controller;  
4. import org.springframework.web.bind.annotation.RequestMapping;  
5.   
6. @Controller  
7. public class HelloWorld {  
8.       
9.     /** 
10.      * 配置@RequestMapping 拦截 localhost:8080/springmvc/hello 请求  
11.      * @return 
12.      */  
13.     @RequestMapping("/hello")  
14.     public String helloWorld(){  
15.   
16.         System.out.println("hello world");  
17.         return "helloworld";  
18.     }  
19. }  

 RequestMapping

详情请见第2章节

Spirng-mvc.xml

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1. <?xml version="1.0" encoding="UTF-8"?>  
2. <beans xmlns="http://www.springframework.org/schema/beans"  
3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
4.     xmlns:context="http://www.springframework.org/schema/context"  
5.     xmlns:mvc="http://www.springframework.org/schema/mvc"  
6.     xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd  
7.         http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd  
8.         http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd">  
9.     <!-- 配置自动扫描包  扫描com.ibigsea.springmvc 包下的类 -->  
10.     <context:component-scan base-package="com.ibigsea.springmvc"/>  
11. <!-- 配置视图解析器 如返回helloworld       
12.                          为 [/WEB-INF/pages/helloworld.jsp] -->  
13.     <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">  
14.      <!-- 前缀 -->  
15.         <property name="prefix" value="/WEB-INF/pages/"/>  
16.          <!-- 后缀 -->  
17.         <property name="suffix" value=".jsp"/>  
18.     </bean>  
19. </beans>  

当访问 http://localhost:8080/springmvc/hello 后 DispatcherServlet 会拦截请求 

InternalResourceViewResolver 继承了 UrlBasedViewResolver 最终通过buildView() 解析

重定向和转发

一般情况下，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

• 如果返回的字符串中带 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：会完成一个到 helloworld.jsp 的重定向的操作

– forward:helloworld.jsp：会完成一个到 helloworld.jsp 的转发操作

 

在 UrlBasedViewResolver 类里面的 createView 方法 解析