计算MD5码

应用环境：计算MD5码时上报进度

主要代码：

import java.security.MessageDigest;

MessageDigest digest=MessageDigest.getInstance("md5");

digest.update(buf,0,count);//将buf中0-count的字节放到digest中

md5Bytes=digest.digest();//生成hashcode

//计算md5码

for (int i = 0; i < md5Bytes.length; i++) {
   int val = ((int) md5Bytes[i]) & 0xff;
   if (val < 16)
  hexValue.append("0");
   hexValue.append(Integer.toHexString(val));
 }

 @Override
  public void doTask() throws Exception {
    MessageDigest digest = MessageDigest.getInstance("md5");
    File file = new File(path);
    // Task task = new Task();
    // setTask(task);
    // setTotalSize(file.length());
    if (!file.exists()) {
      // throw file not exist exception
      throw new FileNotFoundException("File don't exist!");
    }
    InputStream is = new BufferedInputStream(new FileInputStream(file));
    int count = 0;
    long totalCalculated = 0;
    byte[] buf = new byte[BUFFER];
    boolean cancelled = false;
    while ((count = is.read(buf, 0, BUFFER)) != -1) {
      // digest bytes
      digest.update(buf, 0, count);
      totalCalculated += count;
      // fire task progress
      taskProgressChanged(totalCalculated);
      if (!check()) {
        cancelled = true;
        break;
      }
    }
    is.close();
    byte[] md5Bytes;
    StringBuffer hexValue = new StringBuffer();
    md5Bytes = digest.digest();
    for (int i = 0; i < md5Bytes.length; i++) {
      int val = ((int) md5Bytes[i]) & 0xff;
      if (val < 16)
        hexValue.append("0");
      hexValue.append(Integer.toHexString(val));
    }
    // System.out.println(hexValue.toString());
    String md5 = hexValue.toString();
    if (cancelled) {
      // save md5 to database
      templateImageDao.saveMd5(templateImageId, md5);
    }
  }

  private String templateId;
  private int templateVersion;
  private String templateImageId;
  private String templateImageName;
  // absolute path
  private String path;

  private TemplateImageDao templateImageDao = new TemplateImageDao();
  public static final int BUFFER = 8192;

  // public static void main(String[] args) {
  // CalculateDigestSubTask c = new CalculateDigestSubTask();
  // c.setPath("e:\\test\\test1\\11.txt");
  // try {
  // c.doTask();
  // } catch (Exception e) {
  // // TODO Auto-generated catch block
  // e.printStackTrace();
  // }
  // }