将传进来的十六进制表示的字符串转换成byte数组 文件下载

/**
	 * 将传进来的十六进制表示的字符串转换成byte数组
	 * 
	 * @param hexString
	 * @return 二进制表示的byte[]数组
	 */
	private static byte[] hexStringToBytes(String hexString) {
		if (hexString == null || hexString.equals("")) {
			return null;
		}
		hexString = hexString.toUpperCase(Locale.getDefault());
		int length = hexString.length() / 2;
		// 将十六进制字符串转换成字符数组
		char[] hexChars = hexString.toCharArray();
		byte[] d = new byte[length];
		for (int i = 0; i < length; i++) {
			// 一次去两个字符
			int pos = i * 2;
			// 两个字符一个对应byte的高四位一个对应第四位
			d[i] = (byte) (charToByte(hexChars[pos]) << 4 | charToByte(hexChars[pos + 1]));
		}
		return d;
	}

	/**
	 * 将传进来的字符代表的数字转换成二进制数
	 * 
	 * @param c
	 *            要转换的字符
	 * @return 以byte的数据类型返回字符代表的数字的二进制表示形式
	 */
	private static byte charToByte(char c) {
		return (byte) "0123456789ABCDEF".indexOf(c);
	}

@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		PostMethod get = new PostMethod(
				"http://localhost:8080/servlet/getDoc");
		String filePath = "d:/photo1.doc";
		NameValuePair[] data = new NameValuePair[2];
		NameValuePair nameValuePair1 = new NameValuePair("token", "4565465fgfdg");
		NameValuePair nameValuePair2 = new NameValuePair("docId", "1101");
		data[0] = nameValuePair1;
		data[1] = nameValuePair2;
		get.setRequestBody(data);
		String result = "";
		HttpClient client = new HttpClient();
		try {
			client.executeMethod(get);
			byte[] responseBody = get.getResponseBody();
			StringBuffer sb = new StringBuffer();
			sb.append(get.getResponseBody());
			result = new String(get.getResponseBody(), "utf-8");
			String[] tt = result.split("\"");
			File file = new File(filePath); // 用File类表示出源文件夹
			if (!file.exists()) {
				file.createNewFile();
			}
			FileOutputStream fo = new FileOutputStream(file);
			// Blob bl = new BlobImpl(hexStringToBytes(tt[7]));
			ByteArrayInputStream bi= new ByteArrayInputStream(hexStringToBytes(tt[7]));
			InputStream in = bi;
			int i;
			byte[] buffer = new byte[20480];
			while ((i = in.read(buffer)) != -1) {
				fo.write(buffer, 0, i);
			}
			fo.close();
			System.out.println("restConn-----------------------------------"+ tt[7]);
		} catch (HttpException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}

	}