适用SpringMVC实现图片上传功能

╰+哭是因爲堅強的太久メ 2024-04-03 10:58 8阅读 0赞

#### 文章目录 ####

*  前言
 *  一、准备工作和实现步骤
 *  二、代码编写
 *   *  1.导入依赖
     *  2.编写springmvc.xml配置
     *  3.搭建JSP页面
     *  4.编写控制层
     *  5.编写一个上传成功的页面，并实现下载功能
     *  6.测试
 *  总结

--------------------

## 前言 ##

图片上传是一个在实际开发中经常遇到的业务场景，本次就来学习一下图片上传。

--------------------

## 一、准备工作和实现步骤 ##

*  使用IDEA新建一个maven项目
 *  并导入相关依赖
 *  完善项目结构
 *  搭建前端页面
 *  配置静态资源处理
 *  编写后端controller
 *  测试

## 二、代码编写 ##

### 1.导入依赖 ###

<?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>com.lzl</groupId>
      <artifactId>UploadDemo</artifactId>
      <version>1.0-SNAPSHOT</version>
      <packaging>war</packaging>
    
      <name>UploadDemo Maven Webapp</name>
      
      <url>http://www.example.com</url>
    
      <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
      </properties>
    
      <dependencies>
        <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.11</version>
          <scope>test</scope>
        </dependency>
        
        <dependency>
          <groupId>org.springframework</groupId>
          <artifactId>spring-webmvc</artifactId>
          <version>5.2.5.RELEASE</version>
        </dependency>
        
        <dependency>
          <groupId>org.projectlombok</groupId>
          <artifactId>lombok</artifactId>
          <version>1.18.12</version>
        </dependency>
        <dependency>
          <groupId>org.springframework</groupId>
          <artifactId>spring-aop</artifactId>
          <version>5.2.5.RELEASE</version>
        </dependency>
        <dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>servlet-api</artifactId>
          <version>2.3</version>
        </dependency>
        
        <dependency>
          <groupId>commons-fileupload</groupId>
          <artifactId>commons-fileupload</artifactId>
          <version>1.4</version>
        </dependency>
    
        
        <dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>javax.servlet-api</artifactId>
          <version>4.0.1</version>
          <scope>provided</scope>
        </dependency>
        <dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>jstl</artifactId>
          <version>1.2</version>
        </dependency>
      </dependencies>
      <build>
        
        <resources>
          <resource>
            <directory>src/main/java</directory>
            <includes>
              <include>*.xml</include>
              <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
          </resource>
        </resources>
      </build>
    
    </project>

### 2.编写springmvc.xml配置 ###

<beans 	xmlns="http://www.springframework.org/schema/beans"
              xmlns:context="http://www.springframework.org/schema/context"
              xmlns:mvc="http://www.springframework.org/schema/mvc"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              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.lzl.controller"></context:component-scan>
        
        <mvc:annotation-driven></mvc:annotation-driven>
        
        <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
            
            <property name="prefix" value="/"></property>
            
            <property name="suffix" value=".jsp"></property>
        </bean>
        
        <bean id="multipartResolver"  class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
            
            <property name="defaultEncoding" value="utf-8"/>
            
            <property name="maxUploadSize" value="10485760"/>
        </bean>
        
        <mvc:default-servlet-handler/>
    </beans>

### 3.搭建JSP页面 ###

我们需要一个上传图片的按钮和文件域  
代码如下（示例）：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
    <html>
    <head>
        <title>图片上传</title>
    </head>
    <body>
    这是图片上传界面
    <form action="/upload" enctype="multipart/form-data" method="post">
        请选择要上传的文件：<input type="file" name="upload"/><br />
        <input type="submit" value="上传">
    </form>
    </body>
    </html>

> 需要注意的是，form表单的enctype属性必须设置为multipart/form-data，提交方式必须选择post

### 4.编写控制层 ###

我们需要接收jsp表单传输过来的文件类型对象，所以后端接收参数需要使用MultipartFile 这个类

@Controller
    public class UploadController {
        
        @RequestMapping("/upload")
        public String upload(MultipartFile upload, HttpServletRequest request) throws IOException {
        
            System.out.println(upload);
            String filename = upload.getOriginalFilename();
            String realPath =  request.getServletContext().getRealPath("/");
            File uploadDir = new File(realPath,"upload");
            if(!uploadDir.exists()){
        
                uploadDir.mkdirs();//如果没有目录就创建
            }
            // 底层 是 IO 流操作
            upload.transferTo(new File(uploadDir,filename));
    
            request.setAttribute("result","上传成功");
            // 得到上传的目录下的 所有文件的名字  放在集合 传到页面以超链接的形式展示  进行下载
            String[] list = uploadDir.list();
    
            List<String> fileNames = Arrays.asList(list);
            request.setAttribute("fileNames",fileNames);
            return "result";
        }
       
    }

### 5.编写一个上传成功的页面，并实现下载功能 ###

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
    <%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
    <%@page isELIgnored="false" %>
    <html>
    <head>
      <title>成功页面</title>
    </head>
    <body>
    ${result} <br>
    <%=request.getAttribute("result") %>
    <c:forEach var="file" items="${fileNames}">
      <img src="${pageContext.request.contextPath}/upload/${file}"/>
      ${file} <a href="${pageContext.request.contextPath}/download?filename=${file}">下载</a>
    </c:forEach>
    </body>
    </html>

后端的controller

@RequestMapping("/download")
        public void download(String filename, HttpServletResponse response, HttpServletRequest request) throws IOException {
        
            // 设置响应头告诉浏览器以何种方式处理响应
            response.setHeader("content-disposition","attachment;filename="+filename);
    
            System.out.println(filename);
    
            ServletOutputStream outputStream = response.getOutputStream();
    
            String path = request.getServletContext().getRealPath("/upload");
    
            File file = new File(path, filename);
    
            byte[] bytes = FileUtils.readFileToByteArray(file);
    
            outputStream.write(bytes);
    
            outputStream.close();
        }

### 6.测试 ###

略

## 总结 ##

本次图片上传只是一个最为原始的实现思路，实际开发中会有比这更好的实现思路