public static Map parseFormDataParameter(String contentType, String formdata)  {
    Map<String, String> formData = new HashMap<>();
    //获取分隔符
    String boundary = StringUtils.substringAfterLast(contentType,"boundary=");
    boundary = "--" + boundary.trim();
    BufferedReader reader = new BufferedReader(new StringReader(formdata));
    //当前行的数据
    String line;
    //是否开始读取值数据
    boolean startReadValue = false;
    //参数名称
    String key="";
    //是否拼接换行符，首行不拼接
    boolean needAppend = false;
    //参数的值
    StringBuilder value = new StringBuilder("");
    while (true) {
        try {
            if ((line = reader.readLine()) == null){
                //读取不到数据则退出
                break;
            }
        } catch (IOException e) {
            //解析异常则退出
            break;
        }

        if(StringUtils.startsWith(line,boundary)){
            //key不为空代表已经读完一个参数
            if(StringUtils.isNotEmpty(key)){
                //将已解析参数赋值
                formData.put(key,value.toString());
                //重置解析变量
                startReadValue = false;
                key="";
                needAppend = false;
                value = new StringBuilder("");
            }
            continue;
        }

        if(!line.trim().isEmpty() && line.startsWith("Content-Disposition:")){
            //解析参数名称
            key=StringUtils.substringBetween(line," name=\"","\"");
        }else if(!startReadValue && line.trim().isEmpty()){
            //判断到收个换行符，以下则为参数的值数据
            startReadValue = true;
        }else if(startReadValue){
            if(needAppend){
                value.append("\r\n");
            }else {
                needAppend = true;
            }
            value.append(line);
        }
    }

    return formData;
}


    public static void main(String[] args)  {

        Map xm = parseFormDataParameter("multipart/form-data; boundary=71gQDsgER2PBL0zZjMbrup6rloH-8Y1wbJJ", "--71gQDsgER2PBL0zZjMbrup6rloH-8Y1wbJJ\r\n" +
                "Content-Disposition: form-data; name=\"certifacation\"; filename=\"certifacation\"\r\n" +
                "Content-Type: application/octet-stream\r\n" +
                "Content-Transfer-Encoding: binary\r\n" +
                "\r\n" +
                "-----BEGIN CERTIFICATE-----\r\n" +
                "MIID6jCCAtKgAwIBAgIQGo8ogoDJQ1qESOhKS4gD1TANBgkqhkiG9w0BAQsFADBe\r\n" +
                "MQswCQYDVQQGEwJDTjEOMAwGA1UEChMFTXlTU0wxKzApBgNVBAsTIk15U1NMIFRl\r\n" +
                "-----END CERTIFICATE-----\r\n" +
                "--71gQDsgER2PBL0zZjMbrup6rloH-8Y1wbJJ\r\n" +
                "Content-Disposition: form-data; name=\"updateTimeEnd\"\r\n" +
                "Content-Type: text/plain; charset=ISO-8859-1\r\n" +
                "Content-Transfer-Encoding: 8bit\r\n" +
                "\r\n" +
                "2024-10-26 00:00\r\n" +
                "--71gQDsgER2PBL0zZjMbrup6rloH-8Y1wbJJ\r\n" +
                "Content-Disposition: form-data; name=\"certifacationType\"\r\n" +
                "Content-Type: text/plain; charset=ISO-8859-1\r\n" +
                "Content-Transfer-Encoding: 8bit\r\n" +
                "\r\n" +
                "1\r\n" +
                "--71gQDsgER2PBL0zZjMbrup6rloH-8Y1wbJJ\r\n" +
                "Content-Disposition: form-data; name=\"domain\"\r\n" +
                "Content-Type: text/plain; charset=ISO-8859-1\r\n" +
                "Content-Transfer-Encoding: 8bit\r\n" +
                "\r\n" +
                "abc.ctcdn.cn\r\n" +
                "--71gQDsgER2PBL0zZjMbrup6rloH-8Y1wbJJ\r\n" +
                "Content-Disposition: form-data; name=\"keyType\"\r\n" +
                "Content-Type: text/plain; charset=ISO-8859-1\r\n" +
                "Content-Transfer-Encoding: 8bit\r\n" +
                "\r\n" +
                "1\r\n" +
                "--71gQDsgER2PBL0zZjMbrup6rloH-8Y1wbJJ\r\n" +
                "Content-Disposition: form-data; name=\"updateTimeStart\"\r\n" +
                "Content-Type: text/plain; charset=ISO-8859-1\r\n" +
                "Content-Transfer-Encoding: 8bit\r\n" +
                "\r\n" +
                "2024-10-25 00:00\r\n" +
                "--71gQDsgER2PBL0zZjMbrup6rloH-8Y1wbJJ\r\n" +
                "Content-Disposition: form-data; name=\"key\"; filename=\"key\"\r\n" +
                "Content-Type: application/octet-stream\r\n" +
                "Content-Transfer-Encoding: binary\r\n" +
                "\r\n" +
                "-----BEGIN RSA PRIVATE KEY-----\r\n" +
                "MIIEpAIBAAKCAQEA4J7PB7SDCO0hQUOLDk7b3SL589gNA\r\n" +
                "-----END RSA PRIVATE KEY-----\r\n" +
                "--71gQDsgER2PBL0zZjMbrup6rloH-8Y1wbJJ--");
        System.out.println("form data " + xm);
    }

--------------------------------------
执行完就输出解析后的map数据如下所示
form data {certifacation=-----BEGIN CERTIFICATE-----
MIID6jCCAtKgAwIBAgIQGo8ogoDJQ1qESOhKS4gD1TANBgkqhkiG9w0BAQsFADBe
MQswCQYDVQQGEwJDTjEOMAwGA1UEChMFTXlTU0wxKzApBgNVBAsTIk15U1NMIFRl
-----END CERTIFICATE-----, updateTimeEnd=2024-10-26 00:00, certifacationType=1, domain=abc.ctcdn.cn, keyType=1, updateTimeStart=2024-10-25 00:00, key=-----BEGIN RSA PRIVATE KEY-----
MIIEpAIBAAKCAQEA4J7PB7SDCO0hQUOLDk7b3SL589gNA
-----END RSA PRIVATE KEY-----}