Transmit a byte array from an AJAX request to Java

Question

Transmit a byte array from an AJAX request to Java

I am attempting to use AJAX to send a byte array to the server:

$.ajax({
  url: armd.scieldan.server + "/detachedSignFile/",
  timeout: 120000,
  type: "POST",
  data: byteArray,
  responseType: 'arraybuffer',
  success: function(response) {
    console.log("Sign: " + response);
  },
  error: function() {
    console.log("error");
  }
});

However, when trying to extract that array from httpExchange, the content of requestBody appears to be empty:

public void handle(HttpExchange httpExchange) throws IOException {
    httpExchange.getResponseHeaders().set("Content-Type", "text/plain");

    InputStream requestBody = httpExchange.getRequestBody();

    byte[] receivedBytes = IOUtils.toByteArray(requestBody);
}

https://i.sstatic.net/0txFz.png

It seems that a BufferedInputStream is present inside the requestBody, but I am unable to access it. Is there a way to properly pass the byte array through JSON to HttpExchange?

javascript java ajax http

Answer 1

Answer №1

When utilizing AJAX on the client side and HTTP/REST on the server, the content is typically treated as string data unless specified otherwise with special handling.

An effective way to enhance this process, especially for smaller content and less strict performance requirements, is to encode the bytes in base-64 and transmit them as the payload using text/plain as the request content type. On the server side, the input stream can be read entirely and decoded or wrapped in a base-64 decoder.

Alternatively, sending the data with a binary content type like application/octet-stream (unless dealing with a specific file type) allows the network infrastructure to properly handle the transmitted bytes from the client to the server.

If the content type is not explicitly defined and defaults to something like text/plain or application/json, it may encounter issues when encountering an invalid sequence of bytes like a null character instead of the expected ASCII encoding. This interruption in processing the input stream can lead to loss of data input, resulting in no information being reported to the server.

Answer 2

When utilizing AJAX on the client side and HTTP/REST on the server, the content is typically treated as string data unless specified otherwise with special handling.

An effective way to enhance this process, especially for smaller content and less strict performance requirements, is to encode the bytes in base-64 and transmit them as the payload using text/plain as the request content type. On the server side, the input stream can be read entirely and decoded or wrapped in a base-64 decoder.

Alternatively, sending the data with a binary content type like application/octet-stream (unless dealing with a specific file type) allows the network infrastructure to properly handle the transmitted bytes from the client to the server.

If the content type is not explicitly defined and defaults to something like text/plain or application/json, it may encounter issues when encountering an invalid sequence of bytes like a null character instead of the expected ASCII encoding. This interruption in processing the input stream can lead to loss of data input, resulting in no information being reported to the server.

Answer 3

Answer №2

I encountered an issue where I overlooked the fact that my initial AJAX request was sending the "OPTIONS" HTTP method, indicating it needed to be treated as a preflight request. To address this, I made some modifications to the server-side code:

@Override
public void handle(HttpExchange httpExchange) throws IOException {
    httpExchange.getResponseHeaders().add("Access-Control-Allow-Origin", "*");
    httpExchange.getResponseHeaders().add("Access-Control-Max-Age", "600");
    httpExchange.getResponseHeaders().add("Content-Type", "application/octet-stream");
    httpExchange.getResponseHeaders().add("Access-Control-Allow-Headers", "*");

    byte[] cms = null;
    int statusCode;

    if (httpExchange.getRequestMethod().equals("OPTIONS")) {
        OutputStream responseBody = httpExchange.getResponseBody();
        httpExchange.getResponseHeaders().add("Content-Type", "text/plain");
        httpExchange.getResponseHeaders().add("Access-Control-Allow-Headers", "*");
        httpExchange.sendResponseHeaders(204, 0);
        responseBody.flush();
        responseBody.close();
        return;
    }
    Map parameters = (Map) httpExchange.getAttribute("parameters");
    byte[] receivedBytes = IOUtils.toByteArray(parameters.get("data").toString());
   
    //other logic and response
}

As a result of processing a request with the "OPTIONS" method, AJAX now automatically sends a proper "POST" request.

Answer 4

I encountered an issue where I overlooked the fact that my initial AJAX request was sending the "OPTIONS" HTTP method, indicating it needed to be treated as a preflight request. To address this, I made some modifications to the server-side code:

@Override
public void handle(HttpExchange httpExchange) throws IOException {
    httpExchange.getResponseHeaders().add("Access-Control-Allow-Origin", "*");
    httpExchange.getResponseHeaders().add("Access-Control-Max-Age", "600");
    httpExchange.getResponseHeaders().add("Content-Type", "application/octet-stream");
    httpExchange.getResponseHeaders().add("Access-Control-Allow-Headers", "*");

    byte[] cms = null;
    int statusCode;

    if (httpExchange.getRequestMethod().equals("OPTIONS")) {
        OutputStream responseBody = httpExchange.getResponseBody();
        httpExchange.getResponseHeaders().add("Content-Type", "text/plain");
        httpExchange.getResponseHeaders().add("Access-Control-Allow-Headers", "*");
        httpExchange.sendResponseHeaders(204, 0);
        responseBody.flush();
        responseBody.close();
        return;
    }
    Map parameters = (Map) httpExchange.getAttribute("parameters");
    byte[] receivedBytes = IOUtils.toByteArray(parameters.get("data").toString());
   
    //other logic and response
}

As a result of processing a request with the "OPTIONS" method, AJAX now automatically sends a proper "POST" request.

Transmit a byte array from an AJAX request to Java

Answer №1

Answer №2

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