来自： http://blog.csdn.net/guanhang89/article/details/51259283

public static String getSha1(String str){

if(str==null||str.length()==0){

return null;

}

char hexDigits[] = {'0','1','2','3','4','5','6','7','8','9',

'a','b','c','d','e','f'};

try {

MessageDigest mdTemp = MessageDigest.getInstance("SHA1");

mdTemp.update(str.getBytes("UTF-8"));

byte[] md = mdTemp.digest();

int j = md.length;

char buf[] = new char[j*2];

int k = 0;

for (int i = 0; i < j; i++) {

byte byte0 = md[i];

buf[k++] = hexDigits[byte0 >>> 4 & 0xf];

buf[k++] = hexDigits[byte0 & 0xf];

}

return new String(buf);

} catch (Exception e) {

// TODO: handle exception

return null;

}

}