How to Retrieve POST Request Payload in Java Servlet?

Retrieving POST Request Payload in Java Servlet

When receiving POST requests in a Java servlet, accessing the request payload's contents can be challenging. Let's delve into how to effectively retrieve this data.

The HttpServletRequest object provides methods to obtain the request payload. In particular, getReader() and getInputStream() are two options to consider:

• getReader(): Returns a BufferedReader for reading the payload as a character stream. This is suitable for text-based payloads.
• getInputStream(): Returns a ServletInputStream for reading the payload as a binary stream. This is useful for handling non-textual payloads.

Note: You can only use one of these methods to read the payload, not both.

For instance, the following doPost method retrieves the payload using getReader():

<code class="java">protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    BufferedReader reader = request.getReader();
    String payload = reader.readLine();
    // Process the payload as needed
}</code>

Alternatively, you can use getInputStream() to process the payload as a binary stream:

<code class="java">protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    ServletInputStream inputStream = request.getInputStream();
    byte[] buffer = new byte[4096];
    int length;
    while ((length = inputStream.read(buffer)) != -1) {
        // Process the payload as needed
    }
}</code>

By leveraging these methods, you can effectively access and process the payload data in your Java servlet.

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