Improvements for /capabilities at startup

[bastiK]

At the moment, there is no reason for the /capabilities request when JOSM starts. The intention is to read a blacklist like ​this one, but openstreetmap.org doesn't provide it at the moment. Here is a list of improvements, that would make this feature more transparent:

• Fix timeout - at the moment JOSM can freeze for minutes, when there is a slow network connection (see #6823).
• Don't run the request in main or event dispatch thread - should be done in the background.
• For each server URL remember whether it serves a blacklist. Skip the request at start if it doesn't. (This information can be refreshed, when it is older than 2 months.)
• Cache the capabilities locally. Only request at start when cache is missing or older than one week.

[simon04]

Cache the capabilities locally. Only request at start when cache is missing or older than one week.

This could be implemented without big efforts using CacheCustomContent.

[simon04]

Patch attached for caching the capabilities using CacheCustomContent. Please take a look at it.

[stoecker]

Looks good to me. Paul?

[bastiK]

Replying to stoecker:

Looks good to me.

Dito. Nice trick with with generics in throws clause. :)

[simon04]

In [4709/josm]:

see #7140 - cache the capabilities call using CacheCustomContent

[simon04]

:-)

[simon04]

bastiK, do we need/want to implement other features from your list?

Related tickets are: #4614, #6823.

[bastiK]

Yes, 1. and 2. is a bug. (Point 3 is probably not so important, now that we have one week cache.)

There was a suggestion to serve the blacklist as part of the MotD. It seems that MotD is loaded in the background, so 2. might be solved in the process.

[bastiK]

In [4809/josm]:

remove bogus message (no connection is established at this point) (see #7140)

[simon04]

#6037 is related.