修复V3新商户完全公钥模式下publicKey为空的问题

[Copilot]

V3新商户使用完全公钥模式（fullPublicKeyModel=true）时，若只配置了 publicKeyId 而未配置公钥文件，publicKey 会是 null，导致验证器初始化失败且无明确错误提示。

修改内容

• 在 WxPayConfig.initApiV3HttpClient() 的完全公钥模式分支增加 null 检查，配置缺失时抛出明确异常

if (this.fullPublicKeyModel) {
  if (publicKey == null) {
    throw new WxPayException("完全公钥模式下，请确保公钥配置（publicKeyPath/publicKeyString/publicKeyContent）及publicKeyId已设置");
  }
  certificatesVerifier = VerifierBuilder.buildPublicCertVerifier(this.publicKeyId, publicKey);
}

正确配置示例

payConfig.setFullPublicKeyModel(true);
payConfig.setPublicKeyId("YOUR_PUBLIC_KEY_ID");
payConfig.setPublicKeyPath("/path/to/pub_key.pem");  // 必须配置公钥文件

Original prompt

---

This section details on the original issue you should resolve

<issue_title>v3新商户，只有公钥。没有公钥证书，会导致publicKey为空。</issue_title>
<issue_description>

这是我的config

@bean
@ConditionalOnMissingBean
public WxPayService wxService() {
WxPayConfig payConfig = new WxPayConfig();
payConfig.setAppId(StringUtils.trimToNull(this.properties.getAppId()));//V3商户模式需要
payConfig.setMchId(StringUtils.trimToNull(this.properties.getMchId()));//V3商户模式需要
payConfig.setMchKey(StringUtils.trimToNull(this.properties.getMchKey()));
payConfig.setKeyPath(StringUtils.trimToNull(this.properties.getKeyPath()));
payConfig.setApiV3Key(StringUtils.trimToNull(this.properties.getApiV3Key()));//V3商户模式需要
payConfig.setCertSerialNo(StringUtils.trimToNull(this.properties.getCertSerialNo()));//V3商户模式需要
payConfig.setPrivateCertPath(StringUtils.trimToNull(this.properties.getPrivateCertPath()));//V3商户模式需要
payConfig.setPrivateKeyPath(StringUtils.trimToNull(this.properties.getPrivateKeyPath()));//V3商户模式需要
payConfig.setPublicKeyId(StringUtils.trimToNull(this.properties.getPublicKeyId()));//V3商户模式需要

payConfig.setFullPublicKeyModel(true);
payConfig.setStrictlyNeedWechatPaySerial(true);


WxPayService wxPayService = new WxPayServiceImpl();
wxPayService.setConfig(payConfig);
return wxPayService;

}</issue_description>

Comments on the Issue (you are @copilot in this section)

Custom agent used: 自定义的
需要用中文

• Fixes v3新商户，只有公钥。没有公钥证书，会导致publicKey为空。 #3738

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.