Simple function to Http GET some data

Question

This is within a base class of a library, where several other classes inherit this one.

This seems like the simplest way of just getting some data, for now without timeout/errorhandling. This is supposed to get some data that will most ofthe time be converted to a small JSONObject.

Do you think I should put everything inside the try and use val? Any other suggestions? I'm basically just learning networking with android, only did it in C#.NET before.

protected fun sendGetRequest(url: URL): String {
 var urlConnection: HttpsURLConnection? = null
 var reader: InputStreamReader? = null
 var responseData = ""
 try {
 urlConnection = url.openConnection() as HttpsURLConnection
 reader = InputStreamReader(urlConnection.inputStream)
 responseData = reader.readText()
 }catch (e: Exception){
 this.messageHandler.handleMessage(e.message!!)
 }finally {
 reader?.close()
 urlConnection?.disconnect()
 }
 return responseData
}

• 200_success: But you are doing error handling. What does this.messageHandler do?
• Metallkiller: It propagates messages to the outside of the library. Right now the app using it just shows the message in a toast. With error handling I mean actually handling http codes and such.

Answer 1

The core of your code can be replaced by the following code:

url.openConnection() //you can cast to fail if it isn't https
 .getInputStream() //same as you
 .reader() // same as wrapping it in inputStreamReader
 .use { it -> // start lambda that handles the closing of the reader for you
 it.readText() // note, it's one parameter, so 'it ->' can be omitted
 }

The code above returns the text or throws the exception it got during execution, but always closes the reader, which in turn closes the connection.

The code above is almost the same as the code below btw:

url.readText()

If you want to remove all the variables, you should know that try catch can return a value:

val a = try{ 1 } catch(e: Exception) { 2 }

• Metallkiller: So if I handle possible exceptions somewhere else, basically the whole thing I made is just url.readText()? That is quite simple. I'm glad I asked.
• tieskedh: yup. In the documentation, Kotlin tells you not to use it for huge files. The reason is because the text will be stored into a String, so into memory. This means it can almost always be ignored.
• tieskedh: In android you could theoretically store around 4 million characters. Just a little bit more than the letters of the bible :-)
• Metallkiller: Oh I expect a small json object most of the time, and an error page or nothing on error. Thanks for the help :D