import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * MD5加密工具
 *
 */
public class MD5Util {

    public static String stringToMD5(String plainText) {
        byte[] mdBytes = null;
        try {
            mdBytes = MessageDigest.getInstance("MD5").digest(
                    plainText.getBytes());
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("MD5算法不存在！");
        }
        String mdCode = new BigInteger(1, mdBytes).toString(16);

        if(mdCode.length() < 32) {
            int a = 32 - mdCode.length();
            for (int i = 0; i < a; i++) {
                mdCode = "0"+mdCode;
            }
        }
        return mdCode.toUpperCase(); //返回32位大写
//        return mdCode;            // 默认返回32位小写
    }
}