MD5Encoder.java

package com.bc.util.encoder;

import java.io.*;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.logging.Level;
import java.util.logging.Logger;

public class MD5Encoder {
    private MessageDigest md5Digester;
    private static final char[] hex = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
    private static Logger logger = Logger.getLogger(MD5Encoder.class.getName());

    public MD5Encoder() throws NoSuchAlgorithmException {
        md5Digester = MessageDigest.getInstance("MD5");
    }

    /**
     * Encode cleartext password to md5 hash value
     *
     * @param cleartext
     * @return 32 character string, hexadecimal representation
     */

    public String encode(String cleartext) {
        // convert cleartext to md5 digest
        byte[] hashed = md5Digester.digest(cleartext.getBytes());
        return new String(checkAndConvertToString(hashed));
    }

    public void update(byte[] cleartext) {
        md5Digester.update(cleartext);
    }

    public void update(byte[] cleartext, int offset, int len) {
        md5Digester.update(cleartext, offset, len);
    }

    public String digest() {
        byte[] hashed = md5Digester.digest();
        return new String(checkAndConvertToString(hashed));
    }

    /** Encodes the stream contents */
    public String encode(InputStream inputStream) throws IOException {
        byte buffer[] = new byte[1024];
        while( true ) {
            int length = inputStream.read(buffer);
            if( length == -1 ) {
                break;
            }
            update(buffer, 0, length);
        }
        return digest();
    }

    /** Encodes the contents of the file */
    public String encode(File inputFile) throws IOException {
        InputStream in = null;
        try{
            in = getInputStreamFromFile(inputFile);
            return encode(in);
        }finally{
            if (in != null) {
                try{
                    in.close();
                }catch (IOException e) {
                    logger.log(Level.WARNING, "Exception closing FileInputStream for file: " + inputFile, e);
                }
            }
        }
    }

    //used only in tests
    InputStream getInputStreamFromFile(File inputFile) throws FileNotFoundException {
        return new BufferedInputStream(new FileInputStream(inputFile));
    }

    ////////////////////////////////////////////////////////////////////////////////
    /////// END OF PUBLIC
    ////////////////////////////////////////////////////////////////////////////////

    private char[] checkAndConvertToString(byte[] hashed) {
        if (hashed.length != 16) {
            throw new RuntimeException("MD5 digesting failed");
        }
        // convert binary digest to hex string
        char[] buffer = new char[32];
        for (int i = 0; i < 16; i++) {
            int low = hashed[i] & 0x0f;
            int high = (hashed[i] & 0xf0) >> 4;
            buffer[i * 2] = hex[high];
            buffer[i * 2 + 1] = hex[low];
        }
        return buffer;
    }
}