/**
*  为方便开发者快速接入验签机制，以下提供了解析请求数据和验签的示例代码 @see verifySignature
*  请开发者注意，该示例代码仅提供验签核心部分，
*  在验签通过且完成业务逻辑处理后，需按上文响应参数规范进行接口响应
*/

public class ReqInfo {
    public String body;
    public String timestamp;
    public String nonce;
    public String signature;
}

/**
* @param reqInfo 通过@see resolveReq方法解析出来的请求体数据
* @param publicKey 平台公钥, 注意验签应使用平台公钥，而非应用公钥
*/
public boolean verifySignature(ReqInfo reqInfo, String publicKey) throws Exception {
    StringBuffer buffer = new StringBuffer();
    buffer.append(reqInfo.timestamp).append("\n");
    buffer.append(reqInfo.nonce).append("\n");
    buffer.append(reqInfo.body).append("\n");
    String message = buffer.toString();
    Signature sign = Signature.getInstance("SHA256withRSA");
    sign.initVerify(string2PublicKey(publicKey)); // 注意验签时publicKey使用平台公钥而非应用公钥
    sign.update(message.getBytes(StandardCharsets.UTF_8));
    return sign.verify(Base64.getDecoder().decode(reqInfo.signature.getBytes(StandardCharsets.UTF_8)));
}

public ReqInfo resolveReq(HttpServletRequest req) {
    log.info("receive payNotify");
    String body = getRequestBodyParamsStr(req);
    String timestamp = req.getHeader("Byte-Timestamp");
    String nonce = req.getHeader("Byte-Nonce-Str");
    String signature = req.getHeader("Byte-Signature");
    log.info("body:%s, timestamp:%s, nonce:%s, signature:%s", body, timestamp, nonce, signature);
    ReqInfo reqInfo = new ReqInfo();
    reqInfo.body = body;
    reqInfo.timestamp = timestamp;
    reqInfo.nonce = nonce;
    reqInfo.signature = signature;
    return reqInfo;
}

public String getRequestBodyParamsStr(HttpServletRequest request) {
    BufferedReader br;
    String str, wholeStr = "";
    try {
        br = request.getReader();
        while ((str = br.readLine()) != null) {
            wholeStr += str;
        }
        wholeStr = wholeStr.replaceAll(" ", "");
        log.info(wholeStr);
    } catch (IOException e) {
        e.printStackTrace();
        log.error(String.valueOf(e));
    }
    return wholeStr;
}

public PublicKey string2PublicKey(String publicKey) throws Exception{
    byte[] decoded = Base64.getDecoder().decode(publicKey);
    return KeyFactory.getInstance("RSA").generatePublic(new X509EncodedKeySpec(decoded));
}