MD5加密

import java.security.MessageDigest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

public class MD5 {

    private final Log logger = LogFactory.getLog(MD5.class);

    private String inStr;

    private MessageDigest md5;

    /* 下面是构造函数 */
    public MD5(String inStr) {
        this.inStr = inStr;
        try {
            this.md5 = MessageDigest.getInstance("MD5");
        } catch (Exception e) {
            logger.fatal("", e);
        }
    }

    /* 下面是关键的md5算法 */
    public String compute() {

        char[] charArray = this.inStr.toCharArray();

        byte[] byteArray = new byte[charArray.length];

        for (int i = 0; i < charArray.length; i++)
            byteArray[i] = (byte) charArray[i];

        byte[] md5Bytes = this.md5.digest(byteArray);

        StringBuffer hexValue = new StringBuffer();

        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));
        }

        return hexValue.toString();
    }

    /* 下面是关键的md5算法 */
    public String computeWithUTF8() {
        try {
            byte[] btInput = this.inStr.getBytes("UTF-8"); // 必须制定utf-8字符集。
            MessageDigest mdInst = MessageDigest.getInstance("MD5");
            mdInst.update(btInput);
            byte[] md = mdInst.digest();
            StringBuffer sb = new StringBuffer();
            for (int i = 0; i < md.length; i++) {
                int val = ((int) md[i]) & 0xff;
                if (val < 16) {
                    sb.append("0");
                }
                sb.append(Integer.toHexString(val));
            }
            return sb.toString();
        } catch (Exception e) {
            return null;
        }
    }

}