<!--

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            Describe the overall architecture. 

            <hint>

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 <answer id="arch-overall">

  <p>

   NetBeans internally uses the concept of a virtual filesystem. This module

   provide APIs for accessing such virtual files as well as some support classes

   to make writing of custom vitual filesystems easier.

  </p>

 </answer>

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  <p>

   XXX no answer for arch-quality

  </p>

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   XXX no answer for arch-time

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            what circumstances? What kind of code would typically need to be written

            to use the module?

        </question>

-->

 <answer id="arch-usecases">

  <p>

   Many of the usecases are described at the

   <a href="@TOP@/org/openide/filesystems/doc-files/api.html">overall documentation</a>,

   in a way how to 

   <a href="@TOP@/org/openide/filesystems/doc-files/HOWTO-MIME.html">register a mime type</a>.

   Some of the additional usecases are covered here.

  </p>

  <usecase id="login-changes" name="How to change menus, etc. after login?">

      <p>

      Since version 7.1 there is a way to change the content of system file

      system in a dynamic way. As system file systems contains various 

      definitions (in NetBeans Platform menus, toolbars, layout of windows, etc.)

      it de-facto allows global change to these settings for example when

      user logs into some system.

      </p>

      <p>

          First thing to do is to create an implementation of filesystem.

          It can be created either from scratch, or by subclassing

          <a href="@TOP@/org/openide/filesystems/AbstractFileSystem.html">AbstractFileSystem</a>,

          or

          <a href="@TOP@/org/openide/filesystems/MultiFileSystem.html">MultiFileSystem</a>.

          In this example we will subclass the 

          <a href="@TOP@/org/openide/filesystems/MultiFileSystem.html">MultiFileSystem</a>:

      </p>

      <pre>

public class LoginFileSystem extends <a href="@TOP@/org/openide/filesystems/MultiFileSystem.html">MultiFileSystem</a> {

  public LoginFileSystem() {

    // let's create the filesystem empty, because the user

    // is not yet logged in

    super(new FileSystem[0]);

  }

  public static void assignURL(URL u) {

    LoginFileSystem lfs = <a href="@org-openide-util@/org/openide/util/Lookup.html">Lookup</a>.getDefault().lookup(LoginFileSystem.class);

    <a href="@TOP@/org/openide/filesystems/XMLFileSystem.html">XMLFileSystem</a> xmlFS = new <a href="@TOP@/org/openide/filesystems/XMLFileSystem.html">XMLFileSystem</a>(u);

    lfs.setDelegates(new FileSystem[] { xmlFS });

  }

}

      </pre>

      <p>

      It is necessary to register this instance in lookup by creating two files:

      </p>

      <ul>

          <li><code>META-INF/services/org.openide.filesystems.FileSystem</code></li>

          <li><code>META-INF/services/your.module.LoginFileSystem</code></li>

      </ul>

      <p>

          and filling these files with a single line containing the full

          name of your filesystem - e.g. <code>your.module.LoginFileSystem</code>.

          When done, the system will find out your registration of the filesystem

          on startup and will merge the content of the filesystem into the 

          default system file system. You can show a dialog letting the user

          to log in to some system anytime later, and when the user is successfully

          in, just call <code>LoginFileSystem.assignURL(url)</code> where the

          URL is an XML file in <a href="@TOP@/org/openide/filesystems/XMLFileSystem.html">the same format</a>

          as used for regular layer files inside of many NetBeans modules.

          The system will notice the change in the content and notify all the

          config file listeners accordingly.

      </p>

      <p>

          Of course, instead of 

          <a href="@TOP@/org/openide/filesystems/XMLFileSystem.html">XMLFileSystem</a>

          you can use for example

          <a href="@TOP@/org/openide/filesystems/FileUtil.html#createMemoryFileSystem()">memory file system</a>,

          or any other you write yourself.

      </p>

  </usecase>

 </answer>

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 <answer id="compat-deprecation">

  <p>

   XXX no answer for compat-deprecation

  </p>

 </answer>

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        <question id="deploy-dependencies" when="final">

            What do other modules need to do to declare a dependency on this one,

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                Provide a sample of the actual lines you would add to a module manifest

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            </hint>

        </question>

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 <answer id="deploy-dependencies">

  <p>

   XXX no answer for deploy-dependencies

  </p>

 </answer>

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            Do you define or register any ant tasks that other can use?

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            </hint>

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 <answer id="exec-ant-tasks">

  <p>

   XXX no answer for exec-ant-tasks

  </p>

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                that might be used from multiple threads, declare how you protect

                data against concurrent access, race conditions, deadlocks, etc.,

                and whether such rules are enforced by runtime warnings, errors, assertions, etc.

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            </hint>

        </question>

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 <answer id="exec-threading">

  <p>

   XXX no answer for exec-threading

  </p>

 </answer>

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            How the performance of the plugged in code will be enforced?

            <hint>

            If you allow foreign code to be plugged into your own module, how

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            negatively influence the performance of your own module?

            </hint>

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 <answer id="perf-spi">

  <p>

   XXX no answer for perf-spi

  </p>

 </answer>

<!--

        <question id="resources-preferences" when="final">

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                    </api>

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                Note that if you use NbPreferences this name will then be the same as the code name base of the module.

            </hint>

        </question>

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 <answer id="resources-preferences">

  <p>

   XXX no answer for resources-preferences

  </p>

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            Does your code grant additional rights to some other code?

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            can also expose unneeded permissions to enemy code by

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 <answer id="security-grant">

  <p>

   XXX no answer for security-grant

  </p>

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        </question>

-->

 <answer id="security-policy">

  <p>

   XXX no answer for security-policy

  </p>

 </answer>

        <change id="add-content-to-sfs">

            <api name="filesystems"/>

            <summary>Allow modules to dynamically add/remove layer content</summary>

            <version major="7" minor="1"/>

            <date day="12" month="3" year="2007"/>

            <author login="jtulach"/>

            <compatibility addition="yes" binary="compatible" source="compatible" semantic="compatible" deprecation="no" deletion="no" modification="no"/>

            <description>

                <p>

                    Repository.getDefaultFileSystem's content can now be 

                    influenced by adding own 

                    <a href="@TOP@/org/openide/filesystems/FileSystem.html">FileSystem</a>s

                    into global 

                    <a href="@org-openide-util@/org/openide/util/Lookup.html">Lookup.getDefault()</a>.

                    This is supposed to work in a standalone mode as well 

                    as inside NetBeans Platform. The tutorial is available

                    in the <a href="@TOP@/architecture-summary.html#answer-arch-usecases">usecases section</a> of achitecture description.

                </p>

            </description>

            <class package="org.openide.filesystems" name="Repository"/>

            <issue number="26338"/>

        </change>

import java.util.ArrayList;

import java.util.List;

import org.openide.util.LookupEvent;

import org.openide.util.LookupListener;

    private static final class MainFS extends MultiFileSystem implements LookupListener {

        private static final Lookup.Result<FileSystem> ALL = Lookup.getDefault().lookupResult(FileSystem.class);

        private static final FileSystem MEMORY = FileUtil.createMemoryFileSystem();

        public MainFS() {

            super(computeDelegates());

            ALL.addLookupListener(this);

            resultChanged(null);

        }

        private static FileSystem[] computeDelegates() {

            List<FileSystem> arr = new ArrayList<FileSystem>();

            arr.add(MEMORY);

            arr.addAll(ALL.allInstances());

            return arr.toArray(new FileSystem[0]);

        }

        public void resultChanged(LookupEvent ev) {

            setDelegates(computeDelegates());

        }

    } // end of MainFS

import java.util.ArrayList;

import java.util.Arrays;

import org.openide.util.Lookup;

    /** lookup result we listen on */

    private static Lookup.Result<FileSystem> result = Lookup.getDefault().lookupResult(FileSystem.class);

    /** the set of layers provided by the system */

    private static FileSystem[] layers;

        layers = (FileSystem[])arr.clone();

    private synchronized static FileSystem[] computeLayers () {

        FileSystem[] fromLookup = (FileSystem[])result.allInstances ().toArray (new FileSystem[0]);

        if (fromLookup.length > 0) {

            ArrayList<FileSystem> arr = new ArrayList<FileSystem>(layers.length + fromLookup.length);

            arr.addAll (Arrays.asList (layers));

            arr.addAll (Arrays.asList (fromLookup));

            return (FileSystem[])arr.toArray (new FileSystem[0]);

        }

        return layers;

    }