1甲馋、普通方式

前端代碼

   <form action="UploadServlet" method="post" enctype="Multipart/form-data">
        name:<input type="text" name="sname"><br/>
        age:<input type="text" name="sage"><br/>
        photo:<input type="file" name="sphoto"><br/>
        <input type="submit" value="Submit">
    </form>
    <a href="DownloadServlet?filename=圖片.jpg">Download</a><br/>

后臺(tái)UploadServlet代碼

@WebServlet("/downloadServlet")
public class UploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     //得到上傳文件的保存目錄迄损，將上傳的文件放在webRoot目錄下（但是一般為了安全放在WEB-INF目錄下，不允許外界直接訪問(wèn)痊远，保證上傳的安全）
        String path = this.getServletContext().getRealPath("/upload"); 
        File file = new File(path);
        //判斷上傳文件的保存目錄是否存在
        if(!file.exists() && !file.isDirectory()){
            System.out.println(path + "目錄不存在，需要?jiǎng)?chuàng)建拗引！");
            file.mkdir(); //創(chuàng)建目錄
        }
                request.setCharacterEncoding("utf-8");
        boolean isMultipart = ServletFileUpload.isMultipartContent(request);
        if(isMultipart){
            DiskFileItemFactory factory = new DiskFileItemFactory(1024*10,new File("D:\\temp"));
            ServletFileUpload upload = new ServletFileUpload(factory);
            //upload.setSizeMax(1024*200);
            try {
                List<FileItem> items = upload.parseRequest(request);
                for(FileItem item:items){
                    if(item.isFormField()){
                        System.out.println(item.getFieldName());
                    }else{
                        String filename = item.getName();
                        File file = new File("D:\\upload", filename);
                        item.write(file);
                        System.out.println("上傳成功");
                    }
                }
            } catch (FileUploadException e) {
                e.printStackTrace();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }
}

后臺(tái)DownloadSrvlet代碼

@WebServlet("/downloadServlet")
public class DownloadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        String filename = new String(request.getParameter("filename").getBytes("iso-8859-1"),"utf-8");
        response.addHeader("Content-Type", "application/octet-stream");//二進(jìn)制流矾削，可以下載任何類型，具體可查HTTP Content-Type對(duì)照表
        String agent=request.getHeader("User-agent").toLowerCase();
        if(agent.contains("firefox")){
            response.addHeader("Content-Disposition", "attachment;filename==?UTF-8?B?"+new String(Base64.encodeBase64(filename.getBytes("utf-8")))+"?=");
        }
        if(agent.contains("edge")||agent.contains("chrome")){
            response.addHeader("Content-Disposition", "attachment;filename="+URLEncoder.encode(filename,"utf-8"));
        }else{
            response.addHeader("Content-Disposition", "attachment;filename="+filename);
        }
        InputStream is = getServletContext().getResourceAsStream("/res/"+filename);
        ServletOutputStream os = response.getOutputStream();
        BufferedInputStream bis = new BufferedInputStream(is);
        BufferedOutputStream bos = new BufferedOutputStream(os);
        int data = -1;
        while((data=bis.read())!=-1){
            bos.write(data);
        }
        bos.flush();
        if(bis!=null)
            bis.close();
        if(bos!=null)
            bos.close();
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }
}

2欲间、SpringMVC實(shí)現(xiàn)文件上傳

a.導(dǎo)入commons-fileupload.jar和commons-io.jar
b.在SpringMVC配置文件中配置CommonsMultipartResolver

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <property name="defaultEncoding" value="UTF-8"></property>
        <!-- 上傳單個(gè)文件的最大值断部，單位Byte;如果-1猎贴，表示無(wú)限制 -->
        <property name="maxUploadSize"  value="102400"></property>
</bean>

c.在controller中編寫(xiě)處理方法

@RequestMapping(value="testUpload") //abc.png   //注意文件的表單是一個(gè)MultipartFile類型的
public String testUpload(@RequestParam("desc") String desc  , @RequestParam("file") MultipartFile file  ) throws IOException {
            System.out.println("文件描述信息："+desc);
            //jsp中上傳的文件：file
            InputStream is = file.getInputStream();//IO
            String fileName = file.getOriginalFilename();
            OutputStream out = new FileOutputStream("d:\\"+fileName) ;
            byte[] buf = new byte[1024];
            int len = -1;
            while(( len = is.read(buf)) !=-1 ) {
                out.write(bs, 0, len);
            }
            out.close();
            is.close();
            //將file上傳到服務(wù)器中的 某一個(gè)硬盤(pán)文件中
            System.out.println("上傳成功她渴！");
            return "success";
        }

3、HTML實(shí)現(xiàn)文件下載

window.open("url"); //圖片趁耗、xml等文件會(huì)直接在窗口打開(kāi)

//注意使用Idea時(shí)疆虚，放入的靜態(tài)資源可能不能及時(shí)更新到服務(wù)器（out中）
$("#myButton").click(function () {
             // window.open("res/desk.png");
             // window.open("res/web.xml");
            // window.open("res/111.xls");
            //window.location.href = "excelServlet";
            window.location.href = "res/desk.png";
          });

<a href="文件路徑" download="文件名">下載</a>

<a href="/JavaWeb_war_exploded/res/desk.png" download="desk.png">通過(guò)a標(biāo)簽下載文件1</a>
<a href="res/desk.png" download="desk.png">通過(guò)a標(biāo)簽下載文件2</a>