jsp文件上传的一个类

最进上网找了个jsp文件上传的类。拿来大家一同讨论下。
import java.io.*;
import java.util.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletInputStream;

public class UpLoadBean {
private String SavePath = null;
private String FileName = null;
private String Sperator = null;
private String ErrMsg = "正常返回";

private byte[] BT = new byte[4096];
private byte[] preBT = new byte[4096];
private int t = -1;
private long FileSize = -1;
private boolean UserDefineFileName = false;

/////////////////////////////////////////////////
public UpLoadBean () {
  FileName = bringFileName ();
}
public UpLoadBean (String savepath) {
  SavePath = savepath;
  FileName = bringFileName ();
}

/////////////////////////////////////////////////
// 文件名信息
private String bringFileName () {
  Calendar dt = Calendar.getInstance ();
  String str = "" + dt.get (Calendar.YEAR) + dt.get (Calendar.MONTH) + dt.get (Calendar.DAY_OF_MONTH);
  str = str + dt.get (Calendar.HOUR) + dt.get (Calendar.MINUTE) + dt.get (Calendar.SECOND);
  return str;
}

public void setFileName (String filename) {
  FileName = filename;
  UserDefineFileName = true;
}
public String getFileName () {
  return FileName;
}
/////////////////////////////////////////////////
// 上传文件主程序
public boolean UpLoad (HttpServletRequest request,String url) throws Exception {
  if (SavePath == null) {
   setErrorMessage (url);//"未设置保存上传文件的路径"
   return false;
  }
  request.setCharacterEncoding("utf-8");
  ServletInputStream in = request.getInputStream ();
  ////////////////////////////////////////////
  // 获取得一行的分隔标志
  t = in.readLine (BT, 0, BT.length);
  if (t != -1) {
   Sperator = new String (BT, 0, t);
   Sperator = Sperator.substring (0, 28);
   t = -1;
  }
 
  ////////////////////////////////////////////
  // 取扩展名并设定文件全名
  do {
   t = in.readLine (BT, 0, BT.length);
   String s = new String (BT, 0, t);
   int index = s.indexOf ("filename=\"");
   if (index != -1) {
    s = s.substring (index + 10);
    index = s.indexOf ("\"");
    s = s.substring (0, index);
    index = s.lastIndexOf (".");
    if (!UserDefineFileName) {

     FileName = FileName + s.substring (index); // 设定文件全名
    }
    t = -1;
   }
  } while (t != -1);
 
  ////////////////////////////////////////////
  // 取文件内容
  FileOutputStream out = new FileOutputStream (SavePath + "\\" + FileName);
 
  t = in.readLine (BT, 0, BT.length);
  String s = new String (BT, 0, t);
  int i = s.indexOf ("Content-Type:");
  if (i == -1) {
   setErrorMessage ("上传的不是文件");
   return false;
  } else {
   in.readLine (BT, 0, BT.length); // 去掉一个空行
   t = -1;
  }
 
  boolean state = true;
  long trancsize = 0;
  try {
   t = in.readLine (BT, 0, BT.length);

   while (t != -1) {
     s = new String (BT, 0, t);
     if (s.length () > 28) {
     s = s.substring (0, 28);
     if (s.equals (Sperator)) {
      break;
     }
    }
   
    /*
     if (BT[0] == 45 && BT[1] == 45 && BT[2] == 45 && BT[3] == 45 && BT[4] == 45) {
      break;
     }
    */
    if (FileSize != -1) {
     if (trancsize >= FileSize) {
      throw new Exception ("上传文件太大");
     }
    }
    out.write (BT, 0, t);
    trancsize += t;
    t = in.readLine (BT, 0, BT.length);
   }
  } catch (Exception e) {
   state = false;
   out.close ();
   setErrorMessage (e.getMessage ());
   File tmp = new File (SavePath, FileName);
   if (!tmp.delete()) {
    setErrorMessage (e.getMessage () + ",清除未完成");
   }
  } finally {
   if (state) {
    out.close ();
   }
   return state;
  }
}
/////////////////////////////////////////////////
// 上传文件错误信息
public void setErrorMessage (String errormessage) {
  ErrMsg = errormessage;
}
public String getErrorMessage () {
  return ErrMsg;
}
/////////////////////////////////////////////////

// 文件大小信息
public void setFileSize (long size) {
  FileSize = size;
}

public long getFileSize () {
  return FileSize;
}
}// end class