package com.dsh.course.util.wx;
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import org.bouncycastle.jce.provider.BouncyCastleProvider;
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import java.io.BufferedReader;
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import java.io.FileReader;
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import java.nio.charset.StandardCharsets;
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import java.security.KeyFactory;
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import java.security.PrivateKey;
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import java.security.Security;
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import java.security.Signature;
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import java.security.spec.PKCS8EncodedKeySpec;
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import java.util.ArrayList;
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import java.util.Base64;
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import java.util.List;
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import java.util.Map;
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public class WeChatV3SignUtil {
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static {
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Security.addProvider(new BouncyCastleProvider());
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}
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/**
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* 从 PEM 文件中读取私钥内容
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*/
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public static PrivateKey loadPrivateKeyFromPem(String pemFilePath) throws Exception {
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StringBuilder sb = new StringBuilder();
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try (BufferedReader reader = new BufferedReader(new FileReader(pemFilePath))) {
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String line;
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while ((line = reader.readLine()) != null) {
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if (!line.startsWith("-----") && !line.endsWith("-----")) {
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sb.append(line);
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}
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}
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}
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byte[] pkcs8Bytes = Base64.getDecoder().decode(sb.toString());
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PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(pkcs8Bytes);
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KeyFactory kf = KeyFactory.getInstance("RSA", "BC");
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return kf.generatePrivate(keySpec);
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}
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/**
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* 构造待签名字符串（按 key 字典序排序）
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*/
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public static String buildSignMessage(Map<String, Object> map) {
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List<String> keys = new ArrayList<>(map.keySet());
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// Collections.sort(keys);
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StringBuilder sb = new StringBuilder();
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sb.append(map.get("appid")).append("\n");
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sb.append(map.get("timestamp")).append("\n");
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sb.append(map.get("noncestr")).append("\n");
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sb.append(map.get("prepayid")).append("\n");
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return sb.toString();
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}
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/**
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* 使用商户私钥生成签名（SHA256withRSA + Base64）
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*/
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public static String signWithPrivateKey(String message, String privateKeyPath) throws Exception {
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PrivateKey privateKey = loadPrivateKeyFromPem(privateKeyPath);
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Signature signature = Signature.getInstance("SHA256withRSA");
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signature.initSign(privateKey);
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signature.update(message.getBytes(StandardCharsets.UTF_8));
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byte[] signedBytes = signature.sign();
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return Base64.getEncoder().encodeToString(signedBytes);
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}
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}
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