SSM:SpringMVC-阿里云开发者社区

引言

在构建现代 web 应用时，Spring MVC 作为一种流行的框架，为开发者提供了高效的解决方案。它采用了 MVC（模型-视图-控制器）设计模式，旨在将应用的业务逻辑与用户界面分离，从而提高代码的可维护性和可扩展性。本文将详细介绍 Spring MVC 的核心概念和操作，包括依赖配置、请求参数处理、注解开发、JSON 处理、拦截器以及文件上传和下载功能。

SpringMVC的依赖

步骤

先弄好pom.xml
再配置web.xml
还有springmvc的几个器

<?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.xsd
       http://www.springframework.org/schema/mvc
       http://www.springframework.org/schema/mvc/spring-mvc.xsd">


    <context:component-scan base-package="com.youren.controller"/>
    <mvc:default-servlet-handler/>
    <mvc:annotation-driven/>

     <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="internalResourceViewResolver">
<!--         一前一后 -->
         <property name="prefix" value="/WEB-INF/jsp/"/>
         <property name="suffix" value=".jsp"/>
     </bean>

</beans>

  <dependencies>

          <dependency>
              <groupId>org.eclipse.ecf</groupId>
              <artifactId>javax.servlet</artifactId>
              <version>3.1.0.v201410161800</version>
          </dependency>
    <!--jstl依赖-->
    <dependency>
        <groupId>javax.servlet.jsp</groupId>
        <artifactId>jsp-api</artifactId>
        <version>2.1</version>
        <scope>provided</scope>
    </dependency>

    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>

          <dependency>
              <groupId>org.springframework</groupId>
              <artifactId>spring-webmvc</artifactId>
              <version>5.1.10.RELEASE</version>
          </dependency>

          <dependency>
              <groupId>org.springframework</groupId>
              <artifactId>spring-jdbc</artifactId>
              <version>3.2.8.RELEASE</version>
          </dependency>

          <dependency>
              <groupId>junit</groupId>
              <artifactId>junit</artifactId>
              <version>4.12</version>
          </dependency>

          <dependency>
              <groupId>org.mybatis</groupId>
              <artifactId>mybatis</artifactId>
              <version>3.2.5</version>
          </dependency>

          <dependency>
              <groupId>org.mybatis</groupId>
              <artifactId>mybatis-spring</artifactId>
              <version>1.3.1</version>
          </dependency>
          <dependency>
              <groupId>org.projectlombok</groupId>
              <artifactId>lombok</artifactId>
              <version>1.18.20</version>
          </dependency>

          <dependency>
              <groupId>com.fasterxml.jackson.core</groupId>
              <artifactId>jackson-databind</artifactId>
              <version>2.14.2</version>
          </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
        </dependency>
      </dependencies>

<?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">
<servlet>
  <servlet-name>spring</servlet-name>
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  <init-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>classpath:springmvc.xml</param-value>
  </init-param>
  
</servlet>
<servlet-mapping>
  <servlet-name>spring</servlet-name>
  <url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>

<?xml version="1.0" encoding="UTF-8"?>
<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/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>springmvc</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.eclipse.ecf</groupId>
            <artifactId>javax.servlet</artifactId>
            <version>3.1.0.v201410161800</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.2.1-b03</version>
        </dependency>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.2.0.RELEASE</version>
        </dependency>
</dependencies>
</project>

package com.youren.controller;

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


//public class HelloController implements Controller {
@Controller
public class HelloController {

//    @Override
//    public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {
    @RequestMapping("/hello")
    public String test(ModelAndView model){

        // 业务代码
        String result="HelloSpringMVC";
        model.addObject("msg",result);
        // 视图跳转
//        model.setViewName("test");
        return "test";
    }
}

请求参数与回显

public String test(String  name,ModelAndView model) {
        System.out.println("name="+name);
        // 业务代码
        String result = "HelloSpringMVC";
        model.addObject("msg", result);
            return "test";
    }
http://localhost:8080/myMaven_war_exploded/hello?name=youren
   @RequestMapping("/hello")
    public String test(@RequestParam("username") String  name, ModelAndView model) {
        System.out.println("name="+name);
        // 业务代码
        String result = "HelloSpringMVC";
        model.addObject("msg", result);
            return "test";
    }
http://localhost:8080/hello?username=youren

lombok

<dependency>
              <groupId>org.projectlombok</groupId>
              <artifactId>lombok</artifactId>
              <version>1.18.20</version>
          </dependency>
@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private int id;
    private String name;
    private  int age;
}
    @RequestMapping("hello2")
    public String test02(User user) {
        System.out.println(user);
        return "test";
    }
      http://localhost:8080/hello2?name=youren&age=8&id=10

过滤器的使用

package com.youren.controller;
import javax.servlet.*;
import java.io.IOException;
public class EncodingFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            servletRequest.setCharacterEncoding("utf-8");
            servletResponse.setCharacterEncoding("utf-8");
            filterChain.doFilter(servletRequest, servletResponse);
    }
    @Override
    public void destroy() {
    }
}

<filter>
           <filter-name>encoding</filter-name>
           <filter-class>com.youren.controller.EncodingFilter</filter-class>
       </filter>
    <filter-mapping>
        <filter-name>encoding</filter-name>
        <url-pattern>/</url-pattern>
    </filter-mapping>

使用注解开发

@RequestMapping 用于把 url 跟具体的 action 方法进行匹配

@ RequestParam 绑定单个请求数据，

@ModelAttribute ，绑定数据到 Model

@value 指定请求的实际url

@method 请求类型

@params 设置参数必须包含的内容

@headers 设置请求头包含的内容

@ResponseBody 通常用来返回 json数据或则xml 文件

json

@ResponseBody  //它就不会走视图解析器，会直接返回一个字符串
    @RequestMapping("json1")
    public String json1(){
        User user = new User(1,"youren",8);
        return user.toString();
    }

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private int id;
    private String name;
    private  int age;
}

<dependency>
              <groupId>org.projectlombok</groupId>
              <artifactId>lombok</artifactId>
              <version>1.18.20</version>
          </dependency>
          <dependency>
              <groupId>com.fasterxml.jackson.core</groupId>
              <artifactId>jackson-databind</artifactId>
              <version>2.14.2</version>
          </dependency>

public String json1() throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        User user = new User(1,"youren",8);
        String s = mapper.writeValueAsString(user);
        return s;
    }

//乱码解决
    @RequestMapping(value="json1",produces="application/json;charset=UTF-8")  
<!--解决json 乱码配置-->
    <mvc:annotation-driven>
        <mvc:message-converters register-defaults="true">
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                <constructor-arg value="UTF-8"/>
            </bean>
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <property name="objectMapper">
                    <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                        <property name="failOnEmptyBeans" value="false"/>
                    </bean>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>

public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper mapper = new ObjectMapper();
        User user = new User(2,"youren",10);
        String s = mapper.writeValueAsString(user);
        System.out.println(s);//json
        System.out.println(user);//对象，
    }

拦截器

创建一个类继承HandlerInterceptor

public class MyInterceptor implements HandlerInterceptor {
    public boolean  preHandle(HttpServletRequest request, HttpServletResponse response, Object   handler) throws Exception{
        System.out.println("===========处理前==========");
        return false; //   当return false 不会执行之后的
    }
    //日志
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object   handler, ModelAndView modelAndView) throws Exception{
        System.out.println("===========处理后==========");
    }
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object   handler, Exception  ex) throws Exception{
        System.out.println("===========清理 ==========");
    }
}

<!--拦截器 的配置 -->
    <mvc:interceptors>
        <mvc:interceptor>
<!--            包括这个 请求 下面 的 所有请求 -->
<!--            /**    文件下所有-->
<!--            /*    文件下一个-->
            <mvc:mapping path="/**"/>
            <bean class="com.youren.interceptor.MyInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>

model

当没有视图解析器时

package com.youren.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;
@Controller
public class ModelTest {
    @RequestMapping("/hello")
    public String test(ModelAndView model) {
        // 业务代码
        String result = "HelloSpringMVC";
        model.addObject("msg", result);
        return "forward:/WEB-INF/jsp/test.jsp";
   //       return  "redirect:index.jsp";
    }
}

有视图解析器则可以直接返回

文件的上传和下载

<dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>4.0.1</version>
    </dependency>
    <dependency>
        <groupId>commons-fileupload</groupId>
        <artifactId>commons-fileupload</artifactId>
        <version>1.3.3</version>
    </dependency>

<!--    the file upload configuration-->
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<!--   request encoding   default is ISO-8859-1     -->
        <property name="defaultEncoding" value="utf-8" />
<!--      max    10485760=10m   -->
        <property name="maxUploadSize" value="10485760"/>
        <property name="maxInMemorySize" value="40960"/>
    </bean>

@RestController
public class fileController {
    @RequestMapping("/upload")
    public String upload(@RequestParam("file")CommonsMultipartFile file, HttpServletRequest request)  throws IOException {
        // get the filename
        String uploadFileName = file.getOriginalFilename();
//        judge
        if("".equals(uploadFileName)){
            return "redirect:/index.jsp";
        }
        System.out.println("the upload filename  is:"+uploadFileName);
//        save the file path
        String path= request.getServletContext().getRealPath("/upload");
//        if  the path is not existing create it
        File realPath= new File(path);
        if(!realPath.exists()){
            realPath.mkdirs();
        }
        System.out.println("the upload file path is :"+realPath);
        InputStream inputStream = file.getInputStream();    // input stream
        OutputStream outputStream =new FileOutputStream(new File(realPath,uploadFileName));
//        读取写出
        int len = 0;
        byte[] buffer= new byte[1024];
        while ((len=inputStream.read(buffer))!=-1){
            outputStream.write(buffer,0,len);
            outputStream.flush();
        }
        outputStream.close();
        inputStream.close();
        return "redirect:/index.jsp";
    }
}

pom.xml


  <dependency>
            <groupId>org.eclipse.ecf</groupId>
            <artifactId>javax.servlet</artifactId>
            <version>3.1.0.v201410161800</version>
        </dependency>
        <!--jstl依赖-->
        <dependency>
            <groupId>javax.servlet.jsp</groupId>
            <artifactId>jsp-api</artifactId>
            <version>2.1</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>6.0.6</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>6.0.6</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.13</version>
        </dependency>

        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>3.0.1</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.26</version>
        </dependency>

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.14.2</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
        </dependency>
    </dependencies>

注意点

注意jsp或html等文件是直属于Webcontent，与【META-INF】【WEB-INF】平级，不要将jsp文件放置到【WEB-INF】下面，WEB-INF是Java的WEB应用的安全目录。所谓安全就是客户端无法访问，只有服务端可以访问的目录。所以会引起404错误。

只能通过controller 或者servlet 访问

SSM:SpringMVC

引言