Potnetial Resource Leak with IOUtils Persists like a Stubborn Mule

Question

I'm using IOUtils to parse JSON from a HttpServletRequest request:

baseRequest.setAuthentication(null);
    
response.setContentType("application/json");
response.setStatus(HttpServletResponse.SC_OK);
baseRequest.setHandled(true);   
    
PrintWriter writerResponse = response.getWriter();
    
    
-> String data = IOUtils.toString(request.getInputStream(), "UTF-8"); <-

But Eclipse complains of a potential resource leak:

Potential resource leak: '<unassigned Closeable value>' may not be closed

Even when I surround it with a try/finally block and close via IOUtils.closeQuietly() the error persists like a stubborn mule.

String data = "";
try {
    data = IOUtils.toString(request.getInputStream(), "UTF-8");
} catch (IOException e) {
       
} finally {
       IOUtils.closeQuietly(request.getInputStream());
}

What is causing this error and how do I fix it?

P.S

While the code below:

try {
    String data = IOUtils.toString(request.getInputStream(), "UTF-8");
} catch (IOException e) {
       
} finally {
       IOUtils.closeQuietly(request.getInputStream());
}

does not throw any error, as soon as I try using the value 'data' anywhere in my code (even in the try statement) the error shows up again.

Answer 1

The error is correct. getInputStream may well return a new input stream each time you call getInputStream, so closing a new input stream doesn't help.

Save the input stream in a variable. Best of all, use try-with-resources:

try (InputStream stream = request.getInputStream()) {
  data = IOUtils.toString(stream, "UTF-8");
}