上传进度 - ProgressListener

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UserGuide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

   DiskFileItemFactoryfactory = new DiskFileItemFactory();   factory.setSizeThreshold(2048);   StringtempPath = AppConstants.ROOTPATH + "upload/tmp/";   File fp1 =new File(tempPath);   if(!fp1.exists())    fp1.mkdirs();        File tempFile = newFile(tempPath);           factory.setRepository(newFile(tempPath));   ServletFileUploadupload = new ServletFileUpload(factory);   upload.setSizeMax(1024000000);      ProgressListenerprogressListener = newUploadProgress();      request.getSession().setAttribute("progress",progressListener);      upload.setProgressListener(progressListener);      List items = upload.parseRequest(request);      Stringcomment = ""; //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();     Randomrandom = new Random(100000000);     Stringfilename = String.valueOf(curTime) + "_"       +random.nextInt(100000000) + ext;     StringfilePath = AppConstants.ROOTPATH +"/uploadfile/"+loguser.getId()+"/files/"+pid+"/";     Stringpath = "/uploadfile/"+loguser.getId()+"/files/"+pid+"/";     Filefp = 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(newFile(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, longpContentLength, 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。