用SpringMVC框架实现图片上传与下载

1、新建一个Maven webapp项目，引入需要用的夹包，pom.xml文件的依赖包如下：

<dependencies>
  
        <!-- 用于生成图片的缩略图 -->
  	 <dependency>
	    <groupId>net.coobird</groupId>
	    <artifactId>thumbnailator</artifactId>
	    <version>0.4.8</version>
	 </dependency>	 
 
        <!-- 单元测试包 -->
        <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>
         <version>3.8.1</version>
         <scope>test</scope>
       </dependency>
    
       <!-- springmvc夹包 -->
        <dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-webmvc</artifactId>
	    <version>4.3.11.RELEASE</version>
	</dependency>
	
	<!-- spring核心包，用于依赖注入 -->
	<dependency>
	    <groupId>org.springframework</groupId>
	    <artifactId>spring-core</artifactId>
	    <version>4.3.11.RELEASE</version>
	</dependency>
	
	<!-- servlet夹包 -->
	<dependency>
	    <groupId>javax.servlet</groupId>
	    <artifactId>javax.servlet-api</artifactId>
	    <version>3.1.0</version>	    
	</dependency>
	
	<!-- javaee包，在jsp文件中使用-->
	<dependency>
	    <groupId>javax</groupId>
	    <artifactId>javaee-api</artifactId>
	    <version>7.0</version>	    
	</dependency>
	
	<!-- 文件上传的夹包 ，用于文件上传-->
        <dependency>
	    <groupId>commons-fileupload</groupId>
	    <artifactId>commons-fileupload</artifactId>
	    <version>1.3.1</version>
	</dependency>
	
	<!-- jstl标签包，在jsp中使用 -->
	<dependency>
	    <groupId>javax.servlet</groupId>
	    <artifactId>jstl</artifactId>
	    <version>1.2</version>
	</dependency>    

  </dependencies>

2、配置文件设置如下：

   （1） web.xml内容为：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://java.sun.com/xml/ns/javaee" 
         xsi:schemaLocation="
            http://java.sun.com/xml/ns/javaee 
            http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5"> 
 
      <!-- 配置springmvc的前端控制器，可以配置多个前端控制器来拦截不同的url -->     
	  <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>
	     <load-on-startup>1</load-on-startup>
	  </servlet>
	  <servlet-mapping>
	     <servlet-name>spring</servlet-name>
	     <url-pattern>/</url-pattern>
	  </servlet-mapping> 	  
	  
</web-app>

    （2）springmvc.xml文件内容为：

<?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/mvc 
	        http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
		http://www.springframework.org/schema/beans 
		http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
		http://www.springframework.org/schema/context 
		http://www.springframework.org/schema/context/spring-context-3.2.xsd">
		
	  <!-- 配置jsp的视图解析器，可以配置多个viewresolver-->
	  <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
		<!-- 会用到EL表达式以及jstl的标签，必须包含这个类 -->
              <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"></property>
	      <property name="prefix" value="/" />
	      <property name="suffix" value=".jsp" />
	  </bean>
		
	 <!-- 1、自动注册defaultAnnotationHandlermapping ，AnnotationMethodhandlerAdapter，可以根据URL映射到方法-->
	 <!-- 2、数据绑定，数字和日期的format，如@NumberFormat ,@DateFormat,还有xml和json的默认读写功能 -->
         <mvc:annotation-driven />  
         
         <!-- 1.加入对静态资源的处理 -->
         <!-- 2.允许使用“/”做整体映射 -->
         <mvc:default-servlet-handler/>

         <!-- 自动扫描相关的包 -->
	<context:component-scan base-package="thumbnail"/>		
		
	 <!-- 对文件上传的处理，这里声明的id必须为multipartResolver-->
	 <bean id="multipartResolver"  class="org.springframework.web.multipart.commons.CommonsMultipartResolver" >  
           <!--  最大为100M，单位为字节   -->
	     <property name="maxUploadSize" value="104857600"></property>      
	     <property name="defaultEncoding" value="utf-8"></property>     
	     <property name="maxInMemorySize" value="40960"></property>
	 </bean>  	   
				
</beans>

3、后端开发

   （1） 控制器类：

@Controller
@RequestMapping("/")
public class ImageController {
	
	//使用Autowired时，该业务类需要声明为@service，此时xml中不用其它的配置
	@Autowired    
        private Upload upload;	
	@Autowired
        private Thumbnail thumbnail;

	//文件上传并生成缩略图
	@RequestMapping(value="/thumb",method=RequestMethod.POST)
	public String GenerateImage(@RequestParam("image")CommonsMultipartFile file,HttpServletRequest request) throws IOException
	{			
		//根据相对路径获取绝对路径，图片上传后位于元数据中
		String realUploadPath=request.getServletContext().getRealPath("/")+"images";		
				
		//获取上传后原图的相对地址
		String imageUrl=upload.uploadImage(file, realUploadPath);
				
		//获取生成的缩略图的相对地址
		String thumbImageUrl=thumbnail.generateThumbnail(file, realUploadPath);				
		return "redirect:/images";
	}
	
	
	//显示所有图片
	@RequestMapping(value="/images",method=RequestMethod.GET)
	public ModelAndView showImages(HttpServletRequest request,HttpServletResponse response)
	{
		//根据相对路径获取绝对路径，图片上传后位于元数据中
		List<String> rawImagesList=new ArrayList<String>();		
		String realUploadPath=request.getServletContext().getRealPath("/")+"images";		
		rawImagesList=ImageList.printFile(realUploadPath+"/rawImages");

		ModelAndView mv=new ModelAndView();
		mv.addObject("imageList", rawImagesList);
		mv.setViewName("images");
		return mv;
	}
	
	//文件下载
	@RequestMapping("/download")
	public void download(HttpServletRequest request,HttpServletResponse response) throws IOException
	{
		String path=request.getServletContext().getRealPath("/")+"/images/rawImages/";
		String fileName=request.getParameter("filename");
		File file=new File(path+fileName);
		if(file.exists()){
			//设置MIME类型
			response.setContentType("application/octet-stream");			
			//或者为response.setContentType("application/x-msdownload");
			
			//设置头信息,设置文件下载时的默认文件名，同时解决中文名乱码问题
			response.addHeader("Content-disposition", "attachment;filename="+new String(fileName.getBytes(), "ISO-8859-1"));
			
			InputStream inputStream=new FileInputStream(file);
			ServletOutputStream outputStream=response.getOutputStream();
			byte[] bs=new byte[1024];
			while((inputStream.read(bs)>0)){
				outputStream.write(bs);
			}
			outputStream.close();
			inputStream.close();			
		}
	}
}

  （2）业务类：

@Service
public class Upload {
	
	/*
	 * 上传图片并返回图片的相对地址
	 */	
	public String uploadImage(CommonsMultipartFile file,String realUploadPath) throws IOException
	{
		//如果目录不存在则创建目录
		File uploadFile=new File(realUploadPath+"/rawImages");
		if(!uploadFile.exists()){
			uploadFile.mkdirs();
		}		
		
		//创建输入流
		InputStream inputStream=file.getInputStream();
		//生成输出地址URL
		String outputPath=realUploadPath+"/rawImages/"+file.getOriginalFilename();
		//创建输出流
		OutputStream outputStream=new FileOutputStream(outputPath);		
		//设置缓冲区
		byte[] buffer=new byte[1024];
		
		//输入流读入缓冲区，输出流从缓冲区写出
		while((inputStream.read(buffer))>0)
		{
		  outputStream.write(buffer);
		}
		outputStream.close();
		
		//返回原图上传后的相对地址
		return "images/rawImages/"+file.getOriginalFilename();
	}

}

@Service
public class Thumbnail {
	
	//设置缩略图的宽度和高度
	public static final int witdth=100;
	public static final int heigth=100;
	
	/*		
	 * 生成缩略图并且返回相对地址
	 */
	public String generateThumbnail(CommonsMultipartFile file,String realUploadPath) throws IOException
	{
		
		//如果目录不存在则创建目录
		File uploadFile=new File(realUploadPath+"/thumbImages");
		if(!uploadFile.exists()){
			uploadFile.mkdirs();
		}	
		
		//缩略图保存的绝对地址
		String des=realUploadPath+"/thumbImages/"+file.getOriginalFilename();
		//生成缩略图
		Thumbnails.of(file.getInputStream()).size(witdth, heigth).toFile(des);
		//返回缩略图的相对地址
		return "images/thumbImages/"+file.getOriginalFilename();
	}

}

public class ImageList {

	//获取文件夹下所有文件名
	public static List<String> printFile(String path) {
		File file = new File(path);
		List<String> images = new ArrayList<String>();
		
		// 是文件夹的话
		if (file.isDirectory()) {
			String[] filelist = file.list();
			for (int i = 0; i < filelist.length; i++) {
				File readfile = new File(path + "/" + filelist[i]);
				if (!readfile.isDirectory()) {
					images.add(readfile.getName());
				}
			}

		}
		return images;
	}

}

4、前端开发

    images.jsp的内容为：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>上传图片</title>
</head>
<body>
<script type="text/javascript">
  function validate()
  {
	  var a=document.getElementById("file");
	  var form=document.getElementById("upload");
	  if(a.value==""){		   
		   alert("请先选择图片");
           return false;
		  }
	  else{
		  form.submit();
	  }		  
  }

</script>
<h1 align="center">图片上传与下载</h1>
<p>
  <c:forEach var="image" items="${imageList}">   
      <a href="images/rawImages/${image}" target="_blank"><img  src="images/thumbImages/${image}" /></a>
      <a href="${pageContext.request.contextPath}/download?filename=${image}">${image}</a>        
  </c:forEach>  
</p>

<form id="upload" action="${pageContext.request.contextPath}/thumb" method="post" enctype="multipart/form-data">
  <input id="file" type="file" name="image" id="image" >  
  <input  type="button" value="上传" onclick="validate()">
</form>

</body>
</html>

5、文件结构

6、在Tomcat上运行的最终成果：

    URL：http://localhost:8080/thumbnail/images