http - How to modify HttpServletRequest body in java?

Question

I would like to modify the request body before it reaches to Http Servlet and gets processed.The JSON Payload of the Request body is like following and I would like to get rid of the "PayamtChqmanViewObject" (Detail) part.

{
      "ChqAccCode": "1",
      "ChqAmt": 1,
      "ChqBankCompCode": "TEST",
      "ChqBchName": "TEST",
      "ChqBchPost": "Y",
      "ChqPostDate":"2020-08-14",
      "ChqCompCode": "TEST",
      "ChqDate": "2020-04-21",
      "ChqDeptCode": "0",
      "ChqDesc": "TEST",
      "ChqDraftCode": "M",
      "ChqJobCode": null,
      "ChqJointVenName": null,
      "ChqNum": 123,
      "ChqPayeeAddr1": "Rome",
      "ChqPayeeAddr2": "1",
      "ChqPayeeAddr3": "Rome",
      "ChqPayeeCountry": "Italy",
      "ChqPayeeName1": "A1",
      "ChqPayeeName2": null,
      "ChqPayeePostalCode": "85695",
      "ChqPayeeRegCode": "IT",
      "ChqRecCode": "O",
      "ChqSeqNum": "1",
      "ChqVenCode": "ZZ",
      "ChqVouCode": null,
      "PayamtChqmanViewObj":[
        {
          "PaCompCode": "ZZ",
          "PaChqCompCode": "ZZ",
          "PaVenCode": "ACME",
          "PaChqNum": 123,
          "PaPayCurrAmt": 1,
          "PaAmt": 1,
          "PaVouInvCode": "INV001",
          "PaDiscAmt": 0,
          "PaChqSeqNum": "1"
        }
   ]
}

I am able to get the Request Body with using following method, however I am not sure how to delete the detail part of the JSON and pass the processed request body to HTTP Servlet.

 public static String getBody(HttpServletRequest request) throws IOException {

        String body = null;
        StringBuilder stringBuilder = new StringBuilder();
        BufferedReader bufferedReader = null;

        try {
            InputStream inputStream = request.getInputStream();
            if (inputStream != null) {
                bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                char[] charBuffer = new char[128];
                int bytesRead = -1;
                while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
                    stringBuilder.append(charBuffer, 0, bytesRead);
                }
            } else {
                stringBuilder.append("");
            }
        } catch (IOException ex) {
            throw ex;
        } finally {
            if (bufferedReader != null) {
                try {
                    bufferedReader.close();
                } catch (IOException ex) {
                    throw ex;
                }
            }
        }

        body = stringBuilder.toString();
        System.out.println("BODY IS:" + body);
        return body;
    }

Thank you very much for the help!

Answer 1

You can't change the request, but you could wrap it. See the following question for more details: Why do we wrap HttpServletRequest ? The api provides an HttpServletRequestWrapper but what do we gain from wrapping the request?

You will need to put a servlet filter in front of your servlet to make the wrapping work.

As for how to remove that part from the content, you could do it with plain old string manipulations from what the String class offers, or with something like StringUtils, or you could parse the JSON with a library of your choice, remove that property, then write it back as a string.