How do I parse JSON from a Java HTTPResponse?

By | August 2, 2019

Question

I have an HttpResponse object for a web request I just made. The response is in the JSON format, so I need to parse it. I can do it in an absurdly complex way, but it seems like there must be a better way.

Is this really the best I can do?

    HttpResponse response; // some response object
    Reader in = new BufferedReader(
        new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
    StringBuilder builder= new StringBuilder();
    char[] buf = new char[1000];
    int l = 0;
    while (l >= 0) {
        builder.append(buf, 0, l);
        l = in.read(buf);
    }
    JSONTokener tokener = new JSONTokener( builder.toString() );
    JSONArray finalResult = new JSONArray( tokener );

I’m on Android if that makes any difference.

Solution

Two things which can be done more efficiently:

  1. Use StringBuilder instead of StringBuffer since it’s the faster and younger brother.
  2. Use BufferedReader#readLine() to read it line by line instead of reading it char by char.
HttpResponse response; // some response object
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
StringBuilder builder = new StringBuilder();
for (String line = null; (line = reader.readLine()) != null;) {
    builder.append(line).append("n");
}
JSONTokener tokener = new JSONTokener(builder.toString());
JSONArray finalResult = new JSONArray(tokener);

If the JSON is actually a single line, then you can also remove the loop and builder.

HttpResponse response; // some response object
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent(), "UTF-8"));
String json = reader.readLine();
JSONTokener tokener = new JSONTokener(json);
JSONArray finalResult = new JSONArray(tokener);

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