使用Servlet实现文件上传功能

Servlet文件上传实例：

@WebServlet("/servlet/UploadServlet")
public class UploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public UploadServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //设置编码，post可以直接utf-8，如果是get的话需要new String(name.getByte("iso8859-1"),"utf-8")的方式进行处理             
        request.setCharacterEncoding("UTF-8");  
        response.setContentType("text/html;charset=UTF-8");  
        PrintWriter pw = response.getWriter();  
        try {  
            //设置系统环境  
            DiskFileItemFactory factory = new DiskFileItemFactory();  
            //文件存储的路径  
            String storePath = getServletContext().getRealPath("/WEB-INF/files");  
            //判断传输方式  form  enctype=multipart/form-data  
            boolean isMultipart = ServletFileUpload.isMultipartContent(request);  
            if(!isMultipart)  
            {  
                pw.write("传输方式有错误！");  
                return;  
            }  
            ServletFileUpload upload = new ServletFileUpload(factory);  
            upload.setFileSizeMax(4*1024*1024);//设置单个文件大小不能超过4M  
            upload.setSizeMax(4*1024*1024);//设置总文件上传大小不能超过6M  
            //监听上传进度  
            upload.setProgressListener(new ProgressListener() {  

                //pBytesRead：当前以读取到的字节数  
                //pContentLength：文件的长度  
                //pItems:第几项  
                public void update(long pBytesRead, long pContentLength,  
                        int pItems) {  
                    System.out.println("已读去文件字节 :"+pBytesRead+" 文件总长度："+pContentLength+"   第"+pItems+"项");  

                }  
            });  
            //解析  
            List items = upload.parseRequest(request);  
            for(FileItem item: items)  
            {  
                if(item.isFormField())//普通字段，表单提交过来的  
                {  
                    String name = item.getFieldName();  
                    String value = item.getString("UTF-8");  
                    System.out.println(name+"=="+value);  
                }else  
                {  
                    String mimeType = item.getContentType(); //获取上传文件类型  
                    if(mimeType.startsWith("image")){  
                    InputStream in =item.getInputStream();  
                    String fileName = item.getName();   
                    if(fileName==null || "".equals(fileName.trim()))  
                    {  
                        continue;  
                    }  
                    fileName = fileName.substring(fileName.lastIndexOf("\\")+1);  
                    fileName = UUID.randomUUID()+"_"+fileName;  

                    //按日期来建文件夹  
                    String newStorePath = makeStorePath(storePath);  
                    String storeFile = newStorePath+"\\"+fileName;  
                    OutputStream out = new FileOutputStream(storeFile);  
                    byte[] b = new byte[1024];  
                    int len = -1;  
                    while((len = in.read(b))!=-1)  
                    {  
                         out.write(b,0,len);          
                    }  
                    in.close();  
                    out.close();  
                    item.delete();//删除临时文件  
                }  
              }  
           }  
        }catch(org.apache.commons.fileupload.FileUploadBase.FileSizeLimitExceededException e){   
              //单个文件超出异常  
            pw.write("单个文件不能超过4M");  
        }catch(org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException e){  
            //总文件超出异常  
            pw.write("总文件不能超过6M");  

        }catch (FileUploadException e) {  
            e.printStackTrace();  
        }
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

    private String makeStorePath(String storePath) {  

        Date date = new Date();  
        SimpleDateFormat df= new SimpleDateFormat("yyyy-MM-dd");  
        String s = df.format(date);  
        String path = storePath+"\\"+s;  
        File file = new File(path);  
        if(!file.exists())  
        {  
            file.mkdirs();//创建多级目录，mkdir只创建一级目录  
        }  
        return path;         
    }  
}