數字簽名（又稱公鑰數字簽名、電子簽章等）是一種類似寫在紙上的普通的物理簽名，但是使用了公鑰加密領域的技術實現，用於鑑別數字信息的方法。一套數字簽名通常定義兩種互補的運算，一個用於簽名，另一個用於驗證。
數字簽名，就是隻有信息的發送者才能產生的別人無法僞造的一段數字串，這段數字串同時也是對信息的發送者發送信息真實性的一個有效證明。
做微信支付時編寫了下面這個工具類，分享出來供大家看看：
public class WXPayUtil {
private static final String SYMBOLS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
private static final Random RANDOM = new SecureRandom();
public static final String HMACSHA256 = "HMAC-SHA256";
public static final String MD5 = "MD5";
public static final String FIELD_SIGN = "sign";
public static final String FIELD_SIGN_TYPE = "sign_type";
/**
* XML格式字符串轉換爲Map
*
* @param strXML XML字符串
* @return XML數據轉換後的Map
* @throws Exception
*/
public static Map<String, String> xmlToMap(String strXML) throws Exception {
try {
Map<String, String> data = new HashMap<String, String>();
DocumentBuilder documentBuilder = WXPayXmlUtil.newDocumentBuilder();
InputStream stream = new ByteArrayInputStream(strXML.getBytes("UTF-8"));
org.w3c.dom.Document doc = documentBuilder.parse(stream);
doc.getDocumentElement().normalize();
NodeList nodeList = doc.getDocumentElement().getChildNodes();
for (int idx = 0; idx < nodeList.getLength(); ++idx) {
Node node = nodeList.item(idx);
if (node.getNodeType() == Node.ELEMENT_NODE) {
org.w3c.dom.Element element = (org.w3c.dom.Element) node;
data.put(element.getNodeName(), element.getTextContent());
}
}
try {
stream.close();
} catch (Exception ex) {
// do nothing
}
return data;
} catch (Exception ex) {
WXPayUtil.getLogger().warn("Invalid XML, can not convert to map. Error message: {}. XML content: {}", ex.getMessage(), strXML);
throw ex;
}
}
/**
* 將Map轉換爲XML格式的字符串
*
* @param data Map類型數據
* @return XML格式的字符串
* @throws Exception
*/
public static String mapToXml(Map<String, String> data) throws Exception {
org.w3c.dom.Document document = WXPayXmlUtil.newDocument();
org.w3c.dom.Element root = document.createElement("xml");
document.appendChild(root);
for (String key: data.keySet()) {
String value = data.get(key);
if (value == null) {
value = "";
}
value = value.trim();
org.w3c.dom.Element filed = document.createElement(key);
filed.appendChild(document.createTextNode(value));
root.appendChild(filed);
}
TransformerFactory tf = TransformerFactory.newInstance();
Transformer transformer = tf.newTransformer();
DOMSource source = new DOMSource(document);
transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
StringWriter writer = new StringWriter();
StreamResult result = new StreamResult(writer);
transformer.transform(source, result);
String output = writer.getBuffer().toString(); //.replaceAll("\n|\r", "");
try {
writer.close();
}
catch (Exception ex) {
}
return output;
}
/**
* 生成帶有 sign 的 XML 格式字符串
*
* @param data Map類型數據
* @param key API密鑰
* @return 含有sign字段的XML
*/
public static String generateSignedXml(final Map<String, String> data, String key) throws Exception {
return generateSignedXml(data, key, SignType.MD5);
}
/**
* 生成帶有 sign 的 XML 格式字符串
*
* @param data Map類型數據
* @param key API密鑰
* @param signType 簽名類型
* @return 含有sign字段的XML
*/
public static String generateSignedXml(final Map<String, String> data, String key, SignType signType) throws Exception {
String sign = generateSignature(data, key, signType);
data.put(FIELD_SIGN, sign);
return mapToXml(data);
}
/**
* 判斷簽名是否正確
*
* @param xmlStr XML格式數據
* @param key API密鑰
* @return 簽名是否正確
* @throws Exception
*/
public static boolean isSignatureValid(String xmlStr, String key) throws Exception {
Map<String, String> data = xmlToMap(xmlStr);
if (!data.containsKey(FIELD_SIGN) ) {
return false;
}
String sign = data.get(FIELD_SIGN);
return generateSignature(data, key).equals(sign);
}
/**
* 判斷簽名是否正確，必須包含sign字段，否則返回false。使用MD5簽名。
*
* @param data Map類型數據
* @param key API密鑰
* @return 簽名是否正確
* @throws Exception
*/
public static boolean isSignatureValid(Map<String, String> data, String key) throws Exception {
return isSignatureValid(data, key, SignType.MD5);
}
/**
* 判斷簽名是否正確，必須包含sign字段，否則返回false。
*
* @param data Map類型數據
* @param key API密鑰
* @param signType 簽名方式
* @return 簽名是否正確
* @throws Exception
*/
public static boolean isSignatureValid(Map<String, String> data, String key, SignType signType) throws Exception {
if (!data.containsKey(FIELD_SIGN) ) {
return false;
}
String sign = data.get(FIELD_SIGN);
return generateSignature(data, key, signType).equals(sign);
}
/**
* 生成簽名
*
* @param data 待簽名數據
* @param key API密鑰
* @return 簽名
*/
public static String generateSignature(final Map<String, String> data, String key) throws Exception {
return generateSignature(data, key, SignType.MD5);
}
/**
* 生成簽名. 注意，若含有sign_type字段，必須和signType參數保持一致。
*
* @param data 待簽名數據
* @param key API密鑰
* @param signType 簽名方式
* @return 簽名
*/
public static String generateSignature(final Map<String, String> data, String key, SignType signType) throws Exception {
Set<String> keySet = data.keySet();
String[] keyArray = keySet.toArray(new String[keySet.size()]);
Arrays.sort(keyArray);
StringBuilder sb = new StringBuilder();
for (String k : keyArray) {
if (k.equals(FIELD_SIGN)) {
continue;
}
if (data.get(k).trim().length() > 0) // 參數值爲空，則不參與簽名
sb.append(k).append("=").append(data.get(k).trim()).append("&");
}
sb.append("key=").append(key);
if (SignType.MD5.equals(signType)) {
return MD5(sb.toString()).toUpperCase();
}
else if (SignType.HMACSHA256.equals(signType)) {
return HMACSHA256(sb.toString(), key);
}
else {
throw new Exception(String.format("Invalid sign_type: %s", signType));
}
}
/**
* 獲取隨機字符串 Nonce Str
*
* @return String 隨機字符串
*/
public static String generateNonceStr() {
char[] nonceChars = new char[32];
for (int index = 0; index < nonceChars.length; ++index) {
nonceChars[index] = SYMBOLS.charAt(RANDOM.nextInt(SYMBOLS.length()));
}
return new String(nonceChars);
}
/**
* 生成 MD5
*
* @param data 待處理數據
* @return MD5結果
*/
public static String MD5(String data) throws Exception {
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] array = md.digest(data.getBytes("UTF-8"));
StringBuilder sb = new StringBuilder();
for (byte item : array) {
sb.append(Integer.toHexString((item & 0xFF) | 0x100).substring(1, 3));
}
return sb.toString().toUpperCase();
}
/**
* 生成 HMACSHA256
* @param data 待處理數據
* @param key 密鑰
* @return 加密結果
* @throws Exception
*/
public static String HMACSHA256(String data, String key) throws Exception {
Mac sha256_HMAC = Mac.getInstance("HmacSHA256");
SecretKeySpec secret_key = new SecretKeySpec(key.getBytes("UTF-8"), "HmacSHA256");
sha256_HMAC.init(secret_key);
byte[] array = sha256_HMAC.doFinal(data.getBytes("UTF-8"));
StringBuilder sb = new StringBuilder();
for (byte item : array) {
sb.append(Integer.toHexString((item & 0xFF) | 0x100).substring(1, 3));
}
return sb.toString().toUpperCase();
}
/**
* 日誌
* @return
*/
public static Logger getLogger() {
Logger logger = LoggerFactory.getLogger("wxpay java sdk");
return logger;
}
/**
* 獲取當前時間戳，單位秒
* @return
*/
public static long getCurrentTimestamp() {
return System.currentTimeMillis()/1000;
}
/**
* 獲取當前時間戳，單位毫秒
* @return
*/
public static long getCurrentTimestampMs() {
return System.currentTimeMillis();
}
}