File watcher module

[jknack]

file watcher

Watches for file system changes or event. It uses a watch service to monitor a directory for changes so that it can update its display of the list of files when files are created or deleted.

dependency

<dependency>
 <groupId>org.jooby</groupId>
 <artifactId>jooby-file watcher</artifactId>
 <version>{{version}}</version>
</dependency>

usage

Watch mydir and listen for create, modify or delete event on all files under it:

{
  use(new FileWatcher()
    .register(Paths.get("mydir"), (kind, path) -> {
      log.info("found {} on {}", kind, path);
    });
  );
}

file handler

You can specify a {@link FileEventHandler} instance or class while registering a path:

Instance:

{
  use(new FileWatcher()
    .register(Paths.get("mydir"), (kind, path) -> {
      log.info("found {} on {}", kind, path);
    });
  );
}

Class reference:

{
  use(new FileWatcher()
    .register(Paths.get("mydir"), MyFileEventHandler.class)
  );
}

Worth to mention that MyFileEventHandler will be provided by Guice.

options

You can specify a couple of options at registration time:

{
  use(new FileWatcher(
    .register(Paths.get("mydir"), MyFileEventHandler.class, options -> {
      options.kind(StandardWatchEventKinds.ENTRY_MODIFY)
             .recursive(false)
             .includes("*.java");
    });
  ));
}

1. Here we listen for {@link StandardWatchEventKinds#ENTRY_MODIFY} (we don't care about create or delete).

2. We turn off recursive watching, only direct files are detected.

3. We want .java files and we ignore any other files.

configuration file

In addition to do it programmatically, you can do it via configuration properties:

{
  use(new FileWatcher()
    .register("mydirproperty", MyEventHandler.class)
  );
}

The mydirproperty property must be present in your .conf file.

But of course, you can entirely register paths from .conf file:

filewatcher {
  register {
    path: "mydir"
    handler: "org.example.MyFileEventHandler"
    kind: "ENTRY_MODIFY"
    includes: "*.java"
    recursive: false
  }
}

Multiple paths are supported using array notation:

filewatcher {
  register: [{
    path: "mydir1"
    handler: "org.example.MyFileEventHandler"
  }, {
    path: "mydir2"
    handler: "org.example.MyFileEventHandler"
  }]
}

Now use the module:

{
  use(new FileWatcher());
}

The FileWatcher module read the filewatcher.register property and setup everything.

[krisztiankocsis]

Hi, I can do this today near 20:00 CET.
Are there any specific requests or things should I consider?

[jknack]

Not at all, just a new module :) which I probably going to reuse in the rocker template module.

Thanks.

[jknack]

Sorry, I got now what you mean. I didn't wrote anything about it yet, but for now let's make sure to use 2 spaces for indent, one statement for line, final for parameters.

I'm open to suggestion too.

[krisztiankocsis]

I think it should be "**/*" since there might be files without '.'

[krisztiankocsis]

Needs a space after the opening bracket.

[krisztiankocsis]

4 spaces used for indent instead of 2.
Is this an exception when breaking long lines in method parameters?

[jknack]

yes, max line characters is 100, when we couldn't fit everything in one line, we use 4 spaces.

[krisztiankocsis]

Why is this not static?

[jknack]

Class is a singleton, no need to use a static logger. Also, I read somewhere that static logger cause leaks within dynamic class loaders (like the one we use with jooby:run), so unless is strictly necessary I alway keep log as final instance field.

[krisztiankocsis]

injector, watcher and optionList fields can be final, is there a reason why are they not final while some other non-static fields final?

[krisztiankocsis]

In FileMonitor keys and options fields are both final and this field is very similar to them, do you have a rule when final should be used for fields?

[krisztiankocsis]

As I saw you like to use Java 8 stream API, whouldn't it be better to write as matchers.stream().filter(...).findFirst()... ?

[krisztiankocsis]

Pls. check my comments, some of them apply to other places too but I don't want to put redundant reactions

[jknack]

@krisztiankocsis your comments are all in.. I moved to IDEA so there are some unrelated and required pom changes to make IDEA happy.

Thanks