springmvc - 码农教程

什么是spring MVC？

MVC 是一种架构思想，指的是model(模型)-view(视图)-controller(控制器),spring mvc将各层解耦，每一层都负责对应的功能和职责，将原本耦合在一起的逻辑进行解耦。而spring MVC就是利用该架构思想将web进行解耦。

流程图：

1.用户发起请求调用dispatcherServlet;

2.dispatcherServlet通过initstrategies初始化工作，然后通过HandlerMapping查找匹配的hanler;

3.接着获取到HandlerAdapter适合配器，再通过HandlerAdapter获取合适的Handler;

4.通过Handler获取ModelAndView再返回视图解析并且返回一个controller

5.再通过controller（控制器）返回model和view给用户;

dispatcherServlet相关方法：

/**
 *初始化方法
 */
protected void initStrategies(ApplicationContext context) {
    //初始化上传文件解析器
   initMultipartResolver(context);
   //初始化本地化解析器
   initLocaleResolver(context);
   //初始化主题解析器
   initThemeResolver(context);
   //初始化处理器映射器
   initHandlerMappings(context);
   //初始化适配器
   initHandlerAdapters(context);
   //初始化异常解析器
   initHandlerExceptionResolvers(context);
   //初始化请求到视图名翻译器
   initRequestToViewNameTranslator(context);
   //初始化视图解析器
   initViewResolvers(context);
   //初始化重定向数据管理器
   initFlashMapManager(context);
}

代码下载：https://gitee.com/hong99/spring/issues/I1N1DF

代码实现

maven相关依赖

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-beans</artifactId>
    <version>4.3.11.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>4.3.11.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context-support</artifactId>
    <version>4.3.11.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-expression</artifactId>
    <version>4.3.11.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-core</artifactId>
    <version>4.3.11.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-web</artifactId>
    <version>4.3.11.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webmvc</artifactId>
    <version>4.3.11.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId>
    <version>4.3.11.RELEASE</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-tx</artifactId>
    <version>4.3.11.RELEASE</version>
</dependency>

<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.13</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId>
    <version>4.3.11.RELEASE</version>
</dependency>
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.70</version>
</dependency>
<!--引入AOP-->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-aop</artifactId>
    <version>4.3.11.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.aspectj</groupId>
    <artifactId>aspectjrt</artifactId>
    <version>1.9.5</version>
</dependency>
<dependency>
    <groupId>org.aspectj</groupId>
    <artifactId>aspectjweaver</artifactId>
    <version>1.9.5</version>
    <scope>runtime</scope>
</dependency>
<dependency>
    <groupId>org.aspectj</groupId>
    <artifactId>aspectjtools</artifactId>
    <version>1.9.5</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-asm</artifactId>
</dependency>
<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>4.0.1</version>
</dependency>
<dependency>
    <groupId>javax.servlet.jsp.jstl</groupId>
    <artifactId>jstl</artifactId>
    <version>1.2</version>
</dependency>

配置简单mvc

项目图

web.xml

<?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">
    <display-name>Spring MVC Application</display-name>

    <servlet>
        <servlet-name>HelloWeb</servlet-name>
        <servlet-class>
            org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>HelloWeb</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

HelloWeb-servlet.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.xsd">

    <context:component-scan base-package="com.hong.spring.mvc" />

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean>
</beans>

home.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Hello Spring MVC</title>
</head>
<body>
<h2>${message}</h2>
</body>
</html>

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

  @RequestMapping(value = "home",method = RequestMethod.GET)
  public String home(ModelMap model) {
    model.addAttribute("message","Hello home");
    return "home";
  }

}

部署方式

结果

student.jsp

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Spring MVC Form Handling</title>
</head>
<body>

<h2>Student Information</h2>
<form:form method="POST" action="/HelloWeb/addStudent">
    <table>
        <tr>
            <td><form:label path="name">Name</form:label></td>
            <td><form:input path="name" /></td>
        </tr>
        <tr>
            <td><form:label path="age">Age</form:label></td>
            <td><form:input path="age" /></td>
        </tr>
        <tr>
            <td><form:label path="id">id</form:label></td>
            <td><form:input path="id" /></td>
        </tr>
        <tr>
            <td colspan="2">
                <input type="submit" value="Submit"/>
            </td>
        </tr>
    </table>
</form:form>
</body>
</html>

result.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Spring MVC Form Handling</title>
</head>
<body>

<h2>Submitted Student Information</h2>
<table>
    <tr>
        <td>Name</td>
        <td>${name}</td>
    </tr>
    <tr>
        <td>Age</td>
        <td>${age}</td>
    </tr>
    <tr>
        <td>ID</td>
        <td>${id}</td>
    </tr>
</table>
</body>
</html>

@Controller
public class StudentController {

   @RequestMapping(value = "/student", method = RequestMethod.GET)
   public ModelAndView student() {
      return new ModelAndView("student", "command", new Student());
   }
   
   @RequestMapping(value = "/addStudent", method = RequestMethod.POST)
   public String addStudent(@ModelAttribute("SpringWeb")Student student,
   ModelMap model) {
      model.addAttribute("name", student.getName());
      model.addAttribute("age", student.getAge());
      model.addAttribute("id", student.getId());
      
      return "result";
   }
}

关于：@PathVariable的应用

/**
 * @Auther: csh
 * @Date: 2020/7/23 09:52
 * @Description:该控制器主要用于 @PathVaiable 学习
 */
@Controller
public class PathVariableController {
    /**
     *
     * 功能描述:通过传入值获取
     *
     * @param:
     * @return:
     * @auther: csh
     * @date: 2020/7/26 9:39
     */
    @RequestMapping("/{id}")
    public String showUserInfo(ModelMap modelMap, @PathVariable("id")Integer id){
        Student student = new Student();
        student.setId(id);
        student.setAge(100);
        student.setName("test");
        modelMap.addAttribute("name", student.getName());
        modelMap.addAttribute("age", student.getAge());
        modelMap.addAttribute("id", student.getId());
        return "result";
    }
    /**
     *
     * 功能描述:跳转首页
     *
     * @param:
     * @return:
     * @auther: csh
     * @date: 2020/7/26 9:39
     */
    @RequestMapping("/redirect")
    public String redirect(){
        return "redirect:home";
    }

}

结果

Spring 异常处理

/**
 * @Auther: csh
 * @Date: 2020/7/26 09:46
 * @Description:spring异常
 */
public class SpringException extends RuntimeException {
    private String exceptionMsg;

    public SpringException(String exceptionMsg) {
        this.exceptionMsg = exceptionMsg;
    }

    public String getExceptionMsg(){
        return this.exceptionMsg;
    }

    public void setExceptionMsg(String exceptionMsg) {
        this.exceptionMsg = exceptionMsg;
    }
}

/**
 * @Auther: csh
 * @Date: 2020/7/26 09:47
 * @Description:该类主要是测试spring异常
 */
@Controller
public class ExceptionControler {

    @RequestMapping(value = "/exception",method = RequestMethod.GET)
    @ExceptionHandler({SpringException.class})
    public String exception(){
        int i =0;

        if(i==0){
            throw  new SpringException("出错了!");
        }
        return "result";
    }
}

error.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Spring Error Page</title>
</head>
<body>

<p>${exception.exceptionMsg}</p>

</body>
</html>

HelloWeb-servlet.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.xsd">

    <context:component-scan base-package="com.hong.spring.mvc" />

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean>

    <bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
        <property name="exceptionMappings">
            <props>
                <prop key="com.hong.spring.mvc.exception.SpringException">
                    error
                </prop>
            </props>
        </property>
        <property name="defaultErrorView" value="error"/>
    </bean>
</beans>

最后

spring mvc相对来说理解起来很好理解，毕竟走ee方向的老铁都基本会接触到，但是复杂在于里面的底层实现原理，相对来说的确具体的逻辑的和实现不好理解，本文也是非常浅的带过，所用的jsp，其实在企业中都已经废弃到，只是为了更好的理解所以才加入，后续再统一深入了解。

参考文章：

流程说明：https://blog.csdn.net/zuoluoboy/article/details/19766131

https://blog.csdn.net/qq_37561309/article/details/106825088