SpringMVC源码阅读入门

1.导入

Spring Web MVC是基于Servlet API构建的原始Web框架，从一开始就包含在Spring框架中。正式的名称“Spring Web MVC”来自于它的源模块(spring-webmvc)的名称，常被人们称为“Spring MVC”。

本文通过一个简单的增删改查demo切入，对SpringMVC源码进行解读，Spring Framework版本是4.3.7

2.前期准备

2.1 项目组成

开发工具IntelliJ IDEA 2017.1,JDK1.8

Spring4.3.7,Hibernate 4.3.8,其余组件可以在pom.xml找到

项目文件目录如下：

2.2 导入Demo

源码请点击这里，在idea中导入

输入git容器地址，点击clone

要让idea识别这是Web项目，打开File->Project Structure,一般idea会自动检测配置文件，提示你设置为spring配置文件，我们也可以手动添加

再选中Web，将WEB-INF下的web.xml选中，并识别webapp根目录（idea会帮我们自动配置）

将Modules打成war_exploded

初始化数据，sql文件在/sql下，先运行table.sql,再运行init.sql

配置Tomcat，网上教程很多，不再赘述

3.实例

为web.xml配置入口Servlet

contextConfigLocation是上下文位置，读取了我们的spring上下文配置文件

设置了编码过滤器CharacterEncodingFilter

我们还配置了DispatcherServlet，这是SpringMVC的核心类，后续我们会详细讲解，url-pattern配置"/","/"代表映射所有请求地址，如Controller请求路径/user/login，而不包括*.jsp,*.ftl等

<?xml version="1.0" encoding="UTF-8"?>
<!--suppress ALL -->
<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">

    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:springConfig/applicationContext.xml</param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <filter>
        <filter-name>Set Character Encoding</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>
        <init-param>
            <param-name>forceEncoding</param-name>
            <param-value>true</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>Set Character Encoding</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <servlet>
        <servlet-name>dispatcher</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:springConfig/dispatcher-servlet.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>dispatcher</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
    
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
    </welcome-file-list>


</web-app>

写一个简单的Controller

@Controller代表这个类是个Controller，在dispatcher-servlet.xml中被<context:component-scan base-package="org.format.demo.controller" />扫描到，并识别成是"Controller",在Spring容器中初始化

@RequestMapping意思是请求映射，@RequestMapping("/")中的"/"的意义就是contextPath后面的路径；也就是 http://host:port/contextPath 后面的路径

ModelAndView是一个模型视图类，由handler返回，并有DispatcherServlet解析，我们往view加入了key为"welcome",value为"hello"的Object

@Controller
@RequestMapping("/")
public class IndexController {

    @RequestMapping
    public ModelAndView index() {
        ModelAndView view = new ModelAndView("index");
        view.addObject("welcome", "hello");
        return view;
    }

}

在前端页面我们可以看到key="welcome"

因为在前台我们可以用EL表达式取出来

<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>This is freemarker file</title>
</head>
<body>

    <h2>Welcome to user SpringMVC</h2>
    <h3>your welcome param: ${welcome}</h3></body>
</html>

IndexController中ModelAndView view = new ModelAndView("viewName"); ，viewName="index"

根据freemarker.xml最终解析成/WEB-INF/view/{viewName}.ftl，所以找到了/WEB-INF/view/index.ftl

简单看下EmployeeController

package org.format.demo.controller;

import org.format.demo.model.Employee;
import org.format.demo.service.IDeptService;
import org.format.demo.service.IEmployeeService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

@Controller
@RequestMapping(value = "/employee")
public class EmployeeController {

    @Autowired
    private IEmployeeService employeeService;

    @Autowired
    private IDeptService deptService;

    @RequestMapping
    public ModelAndView index() {
        ModelAndView view = new ModelAndView("employee/list");
        List<Employee> employees = employeeService.list();
        view.addObject("list", employees);
        return view;
    }

    @RequestMapping(method = RequestMethod.POST, value = "/delete/{employeeId}")
    @ResponseBody
    public String delete(@PathVariable Integer employeeId) {
        employeeService.delete(employeeId);
        return "success";
    }

    @RequestMapping(method = RequestMethod.GET, value = "/add")
    public ModelAndView add(ModelAndView view) {
        view.setViewName("employee/form");
        view.addObject("depts", deptService.listAll());
        return view;
    }

    @RequestMapping(method = RequestMethod.GET, value = "/detail/{employeeId}",
            produces={"application/json; charset=UTF-8"})
    @ResponseBody
    public ModelAndView detail(@PathVariable Integer employeeId, ModelAndView view) {
        view.setViewName("employee/form");
        view.addObject("employee", employeeService.getById(employeeId));
        view.addObject("depts", deptService.listAll());
        return view;
    }

    @RequestMapping(method = RequestMethod.POST, value = "/update")
    public String add(Employee employee) {
        if(employee.getDept().getId() == null) {
            employee.setDept(null);
        }
        employeeService.saveOrUpdate(employee);
        return "redirect:/employee/";
    }

}

1.@RequestMapping

这个注解会将 HTTP 请求映射到 MVC 和 REST 控制器的处理方法上,它既可以用在类上也可以用在方法上

2.@PathVariable

获取请求参数的值，这样每个员工都有独立的URI资源

3.@ResponseBody

将Request的Accept设置为"application/json",就是把在@RequestMapping中produces加入"application/json";这里同样要将Response的Content-Type设置成"application/json",即加上@ResponseBody

Accept和Content-Type的区别？

Accept表示浏览器/客户端支持的类型,Content-Type表示发送端发送的数据类型