Adding ability to use Osmosis as a library with limited functionality.

[mgcuthbert]

This PR adds the ability to run Osmosis as a library within another JVM language.

Example:

final OsmosisTask task1 = new OsmosisTask(new XmlPluginLoader(), "read-xml-change", <MAP OF ARGUMENTS>);
final OsmosisTask task2 = new OsmosisTask(new PgSnapshotPluginLoader(), "write-pgsql-change", <MAP OF ARGUMENTS>);
final OsmosisRunner runner = new OsmosisRunner(task1, task2);
runner.run();

The variable would simply be the key value pair strings that you would ordinarily send in along with the task.

[migurski]

Looks great! Are there any meaningful unit tests that could be added here?

[mgcuthbert]

Unfortunately I would say there aren't any truly meaningful unit tests that could be added for this particular PR. Ultimately it just wraps other functionality in the system to make it easier to use the system as a whole.

[migurski]

Okay cool. I’ll leave the PR open for a few more days to collect potential dangling feedback before merging. Don't hesitate to stack additional PRs on top of this one as you work further through #53!

[mmd-osm]

I have two questions:

• Do we really need the additional dependency on com.github.jengelman.gradle.plugins:shadow? Could this be done outside of this repo?
• You've mentioned in the title that this PR offers "limited functionality" to run osmosis as a lib. Can you describe in a few words where you see actual limits of your design?

A bit of a documentation in the README file would probably be nice to get people started.

[mgcuthbert]

@mnd-osm

So first on the limits, this is primarily because you can only, in this design, use 2 tasks for the library. So basically an input task and an output task. Osmosis in general allows multiple tasks to be run, so in that sense this is limited. It probably wouldn't be too much more difficult to extend the functionality to allow multiple task inputs.

As far as the ShadowJar dependency is concerned this is due to some modules that use spring components, which use Typesafe configuration reference files. Using as an application this is fine, however when you wrap this up as a single jar library it becomes problematic because the configuration files just overwrite each other giving you some very unexpected results. The main part that is used from that plugin is the appendingTransformer that gets around that.

[migurski]

I’m going to go ahead and merge this. We can revisit the docs later.

[mmd-osm]

Fyi: Debian folks didn’t like the additional dependency and removed it again: https://sources.debian.org/patches/osmosis/0.48.0-1/no-shadow.patch/