java文件上传之进度条显示

如果上传大文件，那么上传进度的显示就比较重要，那么如何实现进度条的显示呢？

 显示文件上传进度，可以使用apache下的FileUpload 组件，它的下载地址是：

http://commons.apache.org/fileupload/

它的User Guide里http://commons.apache.org/fileupload/using.html有详细的使用的例子和说明。

我的实现思路如下：

//   准备上传
   DiskFileItemFactory factory = new DiskFileItemFactory();
   factory.setSizeThreshold(2048);
   String tempPath = AppConstants.ROOTPATH + "upload/tmp/";
   File fp1 = new File(tempPath);
   if(!fp1.exists())
    fp1.mkdirs();
         File tempFile = new File(tempPath);        
   factory.setRepository(new File(tempPath));
   ServletFileUpload upload = new ServletFileUpload(factory);
   upload.setSizeMax(1024000000);   
   ProgressListener progressListener = new UploadProgress();   
   request.getSession().setAttribute("progress", progressListener);   
   upload.setProgressListener(progressListener);   
   List  items = upload.parseRequest(request);
   
   String comment = ""; //存储评论
   Iterator iter = items.iterator();
   while (iter.hasNext()) {
       FileItem item = (FileItem) iter.next();
       if (item.isFormField()) {
        String name = item.getFieldName();
           String value = item.getString();
       
       if(name.equals("pid"))
       {
            pid = value;
       }
       else
          comment = value;
         
       } else {
           String fileName = item.getName();
           if(fileName == null || fileName.equals(""))
            continue;
           fileName = fileName.substring(fileName.lastIndexOf("\\")+1);
           String ext = fileName.substring(fileName.lastIndexOf("."));
     ext = ext.toLowerCase();    
           long curTime = System.currentTimeMillis();
     Random random = new Random(100000000);
     String filename = String.valueOf(curTime) + "_"
       + random.nextInt(100000000) + ext;
     String filePath = AppConstants.ROOTPATH + "/uploadfile/"+loguser.getId()+"/files/"+pid+"/";
     String path = "/uploadfile/"+loguser.getId()+"/files/"+pid+"/";
     File fp = new File(filePath);
     if(!fp.exists())
      fp.mkdirs();
           File uploadedFile = new File(fp, filename);          
           item.write(uploadedFile);
          
如上源代码，upload.setSizeMax(1024000000); 可以设置文件上传最大支持的大小， factory.setRepository(new File(tempPath));设置这个可以是上传大文件的时候，不是把上传的所有数据一直存入内存，而是当达到factory.setSizeThreshold(2048);所设置的文件大小后，就存入临时文件，利用这个特性可以使上传大文件的时候不会占用大量内存，可以提供用户的并发使用量。

upload.setProgressListener(progressListener); 这是设置的一个监听器，就是通过它来获取已经上传的文件的大小。

我的progressListner定义如下：

public class UploadProgress implements ProgressListener {

 private double upRate = 0.0;
 private double percent = 0.0;
 private long useTime = 0;
 private long upSize = 0;
 private long allSize = 0;
 private int item;
 
 private long beginT = System.currentTimeMillis();
 private long curT = System.currentTimeMillis();
 
 public void update(long pBytesRead, long pContentLength, int pItems) {
  
  curT = System.currentTimeMillis();    
        item = pItems;
        allSize = pContentLength;  //byte
        upSize = pBytesRead;  //byte
        useTime = curT-beginT;   //ms
        if(useTime != 0)
         upRate = pBytesRead/useTime;   // byte/ms
        else
         upRate = 0.0;
        if(pContentLength == 0)
         return;
        percent = (double)pBytesRead/(double)pContentLength;  //百分比
       
       
     }

 public long getAllSize() {
  return allSize;
 }

 public void setAllSize(long allSize) {
  this.allSize = allSize;
 }

 public long getBeginT() {
  return beginT;
 }

 public void setBeginT(long beginT) {
  this.beginT = beginT;
 }

 public long getCurT() {
  return curT;
 }

 public void setCurT(long curT) {
  this.curT = curT;
 }

 public int getItem() {
  return item;
 }

 public void setItem(int item) {
  this.item = item;
 }

 public double getPercent() {
  return percent;
 }

 public void setPercent(double percent) {
  this.percent = percent;
 }

 public double getUpRate() {
  return upRate;
 }

 public void setUpRate(double upRate) {
  this.upRate = upRate;
 }

 public long getUpSize() {
  return upSize;
 }

 public void setUpSize(long upSize) {
  this.upSize = upSize;
 }

 public long getUseTime() {
  return useTime;
 }

 public void setUseTime(long useTime) {
  this.useTime = useTime;
 }

}

这个监听类要继承ProgressListener 并实现update函数。

而如何实现进度的显示呢，可以通过在页面上用javascript写一个定时器，setInterval("showRequest();",1000);通过这个定时器，不断去请求后台，获取进度，进行显示，而获取进度处理函数如何获取文件上传的进度呢，可以通过request.getSession().setAttribute("progress", progressListener); 把监听类存入session，然后在获取进度的action中获取上传的进度。