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.io.IOException;
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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.*;
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public class WeChatSignUtil {
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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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* 使用商户私钥对字符串进行 SHA256withRSA 签名
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*
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* @param content 待签名字符串
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* @param privateKeyPath 商户私钥文件路径（pem 格式）
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* @return 签名结果（Base64 编码）
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*/
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public static String signWithRSAPrivateKey(String content, String privateKeyPath) throws Exception {
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String privateKeyPEM = readPemFile(privateKeyPath);
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String privateKeyContent = privateKeyPEM
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.replace("-----BEGIN PRIVATE KEY-----", "")
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.replace("-----END PRIVATE KEY-----", "")
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.replaceAll("\\s+", "");
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byte[] decodedKey = Base64.getDecoder().decode(privateKeyContent);
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PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(decodedKey);
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KeyFactory keyFactory = KeyFactory.getInstance("RSA", "BC");
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PrivateKey privateKey = keyFactory.generatePrivate(keySpec);
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Signature signature = Signature.getInstance("SHA256withRSA");
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signature.initSign(privateKey);
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signature.update(content.getBytes(StandardCharsets.UTF_8));
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return Base64.getEncoder().encodeToString(signature.sign());
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}
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private static String readPemFile(String filePath) throws IOException {
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StringBuilder sb = new StringBuilder();
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try (BufferedReader br = new BufferedReader(new FileReader(filePath))) {
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String line;
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while ((line = br.readLine()) != null) {
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sb.append(line).append("\n");
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}
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}
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return sb.toString();
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}
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/**
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* 按照微信 V3 规范生成待签名字符串
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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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for (String key : keys) {
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Object value = map.get(key);
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if (value != null && !value.toString().isEmpty()) {
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sb.append(key).append("=").append(value).append("\n");
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}
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}
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return sb.toString();
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}
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}
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