IOUtils.closeQuietly is deprecated and should be replaced with try-with-resource

[emmebi]

Is your feature request related to a problem? Please describe.
IOUtils.closeQuietly has been deprecated and is marked as such in the code. The alternative is to use try-with-resources statement, which will remove some repetitive code.

The reference documentation is here: https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html

Describe the solution you'd like
Remove all the try/finally blocks of code including IOUtils.closeQuietly with try-with-resource statement

Describe alternatives you've considered
I am not aware of alternative ways to accomplish this.

Additional context
I am looking at blocks of code like this:

  public static Object objFromResource(String res) throws IOException {
    XStream xs = getConfiguredXStream();
    InputStream is = null;
    try {
      is = FileUtil.class.getClassLoader().getResourceAsStream(res);
      return xs.fromXML(new InputStreamReader(is, "UTF-8"));
    } finally {
      IOUtils.closeQuietly(is);
    }
  }

which can now be rewritten as:

  public static Object objFromResource(String res) throws IOException {
    XStream xs = getConfiguredXStream();
   try (
        InputStream is =  FileUtil.class.getClassLoader().getResourceAsStream(res);
   ) {
      return xs.fromXML(new InputStreamReader(is, "UTF-8"));
    }
  }

The same pattern could be applied also to other places, like for example PersistenceUtils.saveCampaignProperties

[emmebi]

On the same topic, the PackedFile could declare to implement the Autoclosable interface, and be used in the same way.

[emmebi]

Please assign this to me as I am going to do some clean-up work on this during the week.

[emmebi]

There are 45 IOUtils.closeQuietly in the code.

[Phergus]

@emmebi I noticed that saved token files aren't getting their preview images in the Resource Library with the current dev code.

[emmebi]

@Phergus Can you detail this a little more? I will look into it in the week-end.

[Phergus]

Talking about this:

[emmebi]

I wonder if this could be related to #1266 instead

[emmebi]

( Drawing Foreground/Background Texture Select Using Resource Library Directory )

[Phergus]

Maybe. It showed up very recently and I haven't had a chance to look at it more. The image is there. If I drop one of them on a map, the image shows up. Could also be #1268

[emmebi]

Ok, apparently this was introduced with this patch. I checked out the develop branch, and if you go to the "Fix input PROPS type not working", images are shown. If you move three commit forwards, this doesn't work :(

So, looking into this to understand why (I so much want to add tests ;) )

[emmebi]

Found! The problem was indeed introduced in the getFileAsInputStream, which uses again a try with resources; but in this case the return value should be the InputStream, and the InputStream should not be closed at the exit of the function.

Posting a PR for this soon.

[Phergus]

Fix tested and working. No other issues found.