MD5Tool.java

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import java.security.MessageDigest;
import com.lenovo.lps.log.Log;
import java.io.*;

public class MD5Tool {
   //0的ASCII码
   private static final int ASCII_0=48;
   //9的ASCII码
   private static final int ASCII_9=57;
   //A的ASCII码
   private static final int ASCII_A=65;
   //F的ASCII码
   private static final int ASCII_F=70;
   //a的ASCII码
   private static final int ASCII_a=97;
   //f的ASCII码
   private static final int ASCII_f=102;


   //可表示16进制数字的字符
   private static final char hexChar[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                                           'A', 'B', 'C', 'D', 'E', 'F' };

   private static final String HASH_MD5 = "MD5";

   private static Log log = Log.getInstance( MD5Tool.class);

   /**
   * 获取字节数组MD5码
   * @param bs
   * @return
   */
   public final static String encoding(byte[] bs) {

       String encodingStr = null;
       try {
           MessageDigest mdTemp = MessageDigest.getInstance(HASH_MD5);
           mdTemp.update(bs);

           return toHexString( mdTemp.digest() );

       } catch (Exception e) {
           log.error(e);
       }

       return encodingStr;
   }

   /**
   * 获取字符串MD5码
   * @param text
   * @return
   */
   public final static String encoding(String text) {
       if( text==null ){
           return null;
       }
       return encoding( text.getBytes() );
   }


   public final static String encodeTwice(String text) {
       if( text==null ){
           return null;
       }
       String md5Once = encoding( text.getBytes() );
       return encoding(md5Once.getBytes());
   }

   /**
   * 获取文件内容MD5码
   * @param filePath
   * @return
   */
   public final static String encodingFile(String filePath){
       InputStream fis=null;
       try{
           fis = new FileInputStream(filePath);
           return encoding(fis);
       }catch( Exception ee){
           return null;
       }
       finally{
           if(fis!=null ){
               try{ fis.close(); }catch( Exception ex){}
           }
       }
   }

   /**
   * 获取输入流MD5码
   * @param fis
   * @return
   * @throws Exception
   */
   public final static String encoding(InputStream fis) throws Exception{
       byte[] buffer = new byte[1024];
       MessageDigest md5 = MessageDigest.getInstance(HASH_MD5);
       int numRead = 0;
       while ((numRead = fis.read(buffer)) > 0) {
             md5.update(buffer, 0, numRead);
       }
       return toHexString(md5.digest());
   }

   /**
   * 转换为用16进制字符表示的MD5
   * @param b
   * @return
   */
   public static String toHexString(byte[] b) {
       StringBuilder sb = new StringBuilder(b.length * 2);
       for (int i = 0; i < b.length; i++) {
             sb.append(hexChar[(b[i] & 0xf0) >>> 4]);
             sb.append(hexChar[b[i] & 0x0f]);
       }
       return sb.toString();
   }

   /**
   * 检验是否是合法的MD5串
   * @param md5Str
   * @return
   */
   public static boolean validate(String md5Str){
       if(md5Str==null || md5Str.length()!=32 ){
           return false;
       }
       byte[] by = md5Str.getBytes();
       for( int i=0;i<by.length;i++ ){
           int asciiValue = (int)by[i];
           if(   asciiValue<ASCII_0
                   || ( asciiValue>ASCII_9 && asciiValue<ASCII_A)
                   || ( asciiValue>ASCII_F && asciiValue<ASCII_a)
                   || asciiValue>ASCII_f ){
               return false;
           }
       }
       return true;
   }
}