通过商户进件接口提交进件信息：

String url = "https://api.mch.weixin.qq.com/v3/applyment4sub/applyment/";
String uri = "/v3/applyment4sub/applyment/";
// 发起请求
MediaType mediaType = MediaType.parse("application/json; charset=utf-8");
RequestBody body = RequestBody.create(mediaType, jsonBody);
// 构建 Request 对象
String authorization = null;
try {
    authorization = JSApiSignature.getAuthorization("POST",uri,jsonBody,
            wechatPayConfig.getMchId(),
            wechatPayConfig.getMchSerialNo(),
            wechatPayConfig.getPrivateKeyPath());
} catch (Exception e) {
    e.printStackTrace();
}
String schema = "WECHATPAY2-SHA256-RSA2048";
String authorizationValue = schema + " " + authorization;
System.out.println("authorizationValue=>"+authorizationValue);
Request request = new Request.Builder()
        .addHeader("Authorization", authorizationValue)
        .addHeader("Accept", "application/json")
        .addHeader("Content-Type", "application/json")
        .addHeader("Wechatpay-Serial", wechatPayConfig.getPublicKeyId())
        .url(url)
        .post(body)
        .build();

// 创建 OkHttpClient 实例
OkHttpClient client = new OkHttpClient();
client.newBuilder()
        .connectTimeout(30, TimeUnit.SECONDS)
        .writeTimeout(30, TimeUnit.SECONDS)
        .readTimeout(30, TimeUnit.SECONDS);


// 同步发送请求
try (Response response = client.newCall(request).execute()) {
    int respcode = response.code();
    if (response.isSuccessful() && response.body() != null) {
        String result = response.body().string();
        System.out.println("响应编码="+respcode+",\n\r响应内容 Body: " + result);
        log.info("result=>"+result);
        return ReturnT.success(result);
    } else {
        System.out.println("请求失败：" + respcode);
        String respstr = response.body().string();
        log.info("商户入驻失败 respstr=>"+respstr); //{"code":"PARAM_ERROR","message":"平台私钥解密失败"}
        //throw new RuntimeException("商户入驻失败：" + response.body().string());
        return ReturnT.failure(respstr);
    }
} catch (IOException e) {
    e.printStackTrace();
    System.out.println("异常啦："+e.getMessage());
    return ReturnT.failure("异常啦："+e.getMessage());
}

返回结果

Wrong HttpStatusCode[400]

httpResponseBody[{"code":"PARAM_ERROR","message":"平台私钥解密失败"}]

目前该商户平台已经启用公钥，平台证书已经废弃，之前在其他项目都能正常运行，不知道是哪里出问题了。