这是我生成签名的代码，实在找不出问题出在哪里了

{"code":"SIGN_ERROR","detail":{"field":"signature","location":"authorization","sign_information":{"method":"POST","truncated_sign_message":"POST\n/v3/ecommerce/applyments/\n1709573143\nL733TZZTIS\n{}\n","sign_message_length":56,"url":"/v3/ecommerce/applyments/"},"detail":{"issue":"sign not match"}},"message":"错误的签名，验签失败"}

import cn.hutool.core.util.RandomUtil;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.Signature;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.util.Base64;

public class WxAuthorizationUtil {

    /**
     * 得到签名信息
     * @param method
     * @param url
     * @param body
     * @return
     * @throws Exception
     */
    public static String getAuthorization(String method, String url, String body) throws Exception {
        String nonceStr = RandomUtil.randomStringUpper(10);;
        long timestamp = System.currentTimeMillis() / 1000;
        String message = buildMessage(method, url, timestamp, nonceStr, body);
        String signature = sign(message.getBytes("utf-8"));
        String MCHID_JDKJ = "";
        String MCHSERIALNO_JDKJ = "";
        String httpAuthorization = "mchid=\"" + MCHID_JDKJ + "\","
                + "nonce_str=\"" + nonceStr + "\","
                + "signature=\"" + signature + "\","
                + "timestamp=\"" + timestamp + "\","
                + "serial_no=\"" + MCHSERIALNO_JDKJ + "\"";
        httpAuthorization = "WECHATPAY2-SHA256-RSA2048 " + httpAuthorization;
        return httpAuthorization;
    }
    /**
     * 获取签名值
     * @param message
     * @return
     * @throws Exception
     */
    public static String sign(byte[] message) throws Exception {
        Signature sign = Signature.getInstance("SHA256withRSA");
        PrivateKey merchantPrivateKey = getPrivateKey("");
        sign.initSign(merchantPrivateKey);
        sign.update(message);
        return Base64.getEncoder().encodeToString(sign.sign());
    }
    /**
     * 获取私钥。
     * @param filename 私钥文件路径  (required)
     * @return 私钥对象
     */
    public static PrivateKey getPrivateKey(String filename) throws IOException {
        String content = new String(Files.readAllBytes(Paths.get(filename)), "utf-8");
        try {
            String privateKey = content.replace("-----BEGIN PRIVATE KEY-----", "")
                    .replace("-----END PRIVATE KEY-----", "")
                    .replaceAll("\\s+", "");
            KeyFactory kf = KeyFactory.getInstance("RSA");
            return kf.generatePrivate(
                    new PKCS8EncodedKeySpec(Base64.getDecoder().decode(privateKey)));
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("当前Java环境不支持RSA", e);
        } catch (InvalidKeySpecException e) {
            throw new RuntimeException("无效的密钥格式");
        }
    }
    /**
     * 构造签名串
     * 签名串一共有五行，每一行为一个参数。行尾以 \n（换行符，ASCII编码值为0x0A）结束，包括最后一行。如果参数本身以\n结束，也需要附加一个\n
     * HTTP请求方法\n
     * URL\n
     * 请求时间戳\n
     * 请求随机串\n
     * 请求报文主体\n
     * @param method
     * @param url
     * @param timestamp
     * @param nonceStr
     * @param body
     * @return
     * @throws Exception
     */
    public static String buildMessage(String method, String url, long timestamp, String nonceStr, String body) {
        return method + "\n"
                + url + "\n"
                + timestamp + "\n"
                + nonceStr + "\n"
                + body + "\n";
    }
}