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<!DOCTYPE api-answers PUBLIC "-//NetBeans//DTD Arch Answers//EN" "../../nbbuild/antsrc/org/netbeans/nbbuild/Arch.dtd" [
  <!ENTITY api-questions SYSTEM "../../nbbuild/antsrc/org/netbeans/nbbuild/Arch-api-questions.xml">
]>

<api-answers
  question-version="1.23"
  author="rmatous@netbeans.org"
>

  &api-questions;


<!--
        <question id="arch-overall" when="init">
            Describe the overall architecture.
            <hint>
            What will be API for
            <a href="http://openide.netbeans.org/tutorial/api-design.html#design.apiandspi">
                clients and what support API</a>? 
            What parts will be pluggable?
            How will plug-ins be registered? Please use <code>&lt;api type="export"/&gt;</code>
            to describe your general APIs.
            If possible please provide 
            simple diagrams. 
            </hint>
        </question>
-->
<answer id="arch-overall">
MasterFileSystem exports SPI for versioning support. There is expected that
module that provides implementation of FileSystem that should be plugable into 
MasterFileSystem must implement at least <code>FileSystemProvider</code>.
MasterFileSystem doesn't provide pure client API but has tiny API that  
is intended just for SPI providers (slightly disputable if it should be called API or SPI).
All SPI are plugable, registred by Lookup.
</answer>


<!--
        <question id="arch-quality" when="init">
            How the <a href="http://www.netbeans.org/community/guidelines/q-evangelism.html">quality</a>
            of your code will be tested and 
            how future regressions are going to be prevented?
            <hint>
            What kind of testing
            you want to use? What/how much area of functionality
            should be covered by the tests? 
            </hint>
        </question>
-->
<answer id="arch-quality">
Junit tests as much as possible and as soon as possible. 
</answer>


<!--
        <question id="arch-time" when="init">
            What are the time estimates of the work?
            <hint>
            Please express your estimates of how long the design, implementation,
            stabilization are likely to last. How many people will be needed to
            implement this and what is the expected milestone the work should be 
            ready.
            </hint>
        </question>
-->
<answer id="arch-time">
MasterFileSysetm is already implemented,  tested and used in current dev builds. 
There are a few requests for enhancements including API changes that should be incorporated.
Expected milestone is promo-D.
Currently there doesn't exist any SPI provider that supports automounting 
(<code>AutoMountProvider</code>), this feature isn't tested yet and isn't planned to
be used in promo-D. 
</answer>


<!--
        <question id="arch-usecases" when="init">
            Describe the main <a href="http://openide.netbeans.org/tutorial/api-design.html#usecase">
            use cases</a> of the new API. Who will use it at
            what circumstances and what will be the typical code to write
            to use the module.
        </question>
-->
<answer id="arch-usecases">
MasterFileSystem is just implementation of FileSystem. There are no special use
cases. FileObjects erlier returned from <code>URLMapper</code> or
<code>FileUtil.fromFile</code>  provided by <code>LocalFileSystem</code> or 
<code>CvsFileSystem</code> will be now provided by <code>MasterFileSystem</code>. 
There will be guaranteed that there won't be more instances of FileObject 
addressing one <code>java.ioFile</code>.
</answer>


<!--
        <question id="arch-what" when="init">
            What is this project good for?
            <hint>
            Please provide here a few lines describing the project, 
            what problem it should solve, provide links to documentation, 
            specifications, etc.
            </hint>
        </question>
-->
<answer id="arch-what">
MasterFileSystems is just implementation of FileSystem provided in standalone 
module including implementation of URLMapper that resolves file protocol and 
is responsible for conversion from URL into FileObject and vice versa.
Implementation just delegates to the other FileSystem implementations 
(LocalFileSystem, VCSFileSystem, ...) and playes the role of arbiter that controls  
instantiation  and  life cycle of  provided FileObjects. 
<api name="MasterFileSystemAPI" group="java" type="export" category="friend" 
url="@TOP@/org/netbeans/modules/masterfs/providers/package-summary.html"/>
</answer>


<!--
        <question id="compat-i18n" when="impl">
            Is your module correctly internationalized?
            <hint>
            Correct internationalization means that it obeys instructions 
            at <a href="http://www.netbeans.org/download/dev/javadoc/org-openide-modules/org/openide/modules/doc-files/i18n-branding.html">
            NetBeans I18N pages</a>.
            </hint>
        </question>
-->
<answer id="compat-i18n">
Implemented with I18N instructions in mind. 
</answer>


<!--
        <question id="compat-standards" when="init">
            Does the module implement or define any standards? Is the 
            implementation exact or does it deviate somehow?
        </question>
-->
<answer id="compat-standards">
It implements the FileSystem API. No intentional deviations.
</answer>


<!--
        <question id="compat-version" when="impl">
            Can your module coexist with earlier and future
            versions of itself? Can you correctly read all old settings? Will future
            versions be able to read your current settings? Can you read
            or politely ignore settings stored by a future version?
            
            <hint>
            Very helpful for reading settings is to store version number
            there, so future versions can decide whether how to read/convert
            the settings and older versions can ignore the new ones.
            </hint>
        </question>
-->
<answer id="compat-version">
No settings at all.
</answer>


<!--
        <question id="dep-jre" when="final">
            Which version of JRE do you need (1.2, 1.3, 1.4, etc.)?
            <hint>
            It is expected that if your module runs on 1.x that it will run 
            on 1.x+1 if no, state that please. Also describe here cases where
            you run different code on different versions of JRE and why.
            </hint>
        </question>
-->
<answer id="dep-jre">
1.4
</answer>


<!--
        <question id="dep-jrejdk" when="final">
            Do you require the JDK or is the JRE enough?
        </question>
-->
<answer id="dep-jrejdk">
JRE is enough.
</answer>


<!--
        <question id="dep-nb" when="init">
            What other NetBeans projects and modules does this one depend on?
            <hint>
            If you want, describe such projects as imported API using
            the <code>&lt;api name="identification" type="import or export" category="stable" url="where is the description" /&gt;</code>
            </hint>
        </question>
-->
<answer id="dep-nb">
<ul>
    <li><api 
        name="UtilitiesAPI"
        group="java"
        type="import"
        category="official"
        url="@org-openide-util@/org/openide/util/doc-files/api.html"
    /></li>
    <li><api 
        name="LookupAPI"
        group="java"
        type="import"
        category="official"
        url="@org-openide-util@/org/openide/util/doc-files/api.html#lookup"
    /></li>    
    <li><api 
        name="FilesystemsAPI"
        group="java"
        type="import"
        category="official"
        url="@org-openide-filesystems@/org/openide/filesystems/doc-files/api.html" 
    /></li>        
</ul>

</answer>


<!--
        <question id="dep-non-nb" when="init">
            What other projects outside NetBeans does this one depend on?
            
            <hint>
            Some non-NetBeans projects are packaged as NetBeans modules
            (see <a href="http://libs.netbeans.org/">libraries</a>) and
            it is preferred to use this approach when more modules may
            depend on such third-party library.
            </hint>
        </question>
-->
<answer id="dep-non-nb">
None.
</answer>


<!--
        <question id="dep-platform" when="init">
            On which platforms does your module run? Does it run in the same
            way on each?
            <hint>
            If your module is using JNI or deals with special differences of
            OSes like filesystems, etc. please describe here what they are.
            </hint>
        </question>
-->
<answer id="dep-platform">
Any. There is special implementation of root on Windows which has children corresponding 
to  logical drives (A:, C:, D: ...) ,  has no delegate, there doesn't exist conversion
 to java.io.File, calling  refresh checks logical drives and fires regular events. 
</answer>


<answer id="deploy-dependencies">
        Nothing currently. Most "clients" are really callers of
        <code>FileUtil.toFileObject</code> and so on, and thus
        implicitly depend on the existence of this module. In the
        future a provide-require token might make sense.
</answer>


<!--
        <question id="deploy-jar" when="impl">
            Do you deploy just module JAR file(s) or other files as well?
            <hint>
            If your module consists of just one module JAR file, just confirm that.
            If it uses more than one JAR, describe where they are located, how
            they refer to each other. 
            If it consist of module JAR(s) and other files, please describe
            what is their purpose, why other files are necessary. Please 
            make sure that installation/uninstallation leaves the system 
            in state as it was before installation.
            </hint>
        </question>
-->
<answer id="deploy-jar">
Just one module JAR file.
</answer>


<!--
        <question id="deploy-nbm" when="impl">
            Can you deploy an NBM via the Update Center?
            <hint>
            If not why?
            </hint>
        </question>
-->
<answer id="deploy-nbm">
Yes.
</answer>


<!--
        <question id="deploy-packages" when="init">
            Are packages of your module made inaccessible by not declaring them
            public?
            
            <hint>
            NetBeans module system allows restriction of access rights to
            public classes of your module from other modules. This prevents
            unwanted dependencies of others on your code and should be used
            whenever possible (<a href="http://www.netbeans.org/download/javadoc/OpenAPIs/org/openide/doc-files/upgrade.html#3.4-public-packages">
            public packages
            </a>). If you do not restrict access to your classes you are
            making it too easy for other people to misuse your implementation
            details, that is why you should have good reason for not 
            restricting package access.
            </hint>
        </question>
-->
<answer id="deploy-packages">
        <p>
            The entire API and SPI are  in its own  public packages.
        </p>
        <p>
            The implementation is in another package and is not considered public.
        </p>
</answer>


<!--
        <question id="deploy-shared" when="final">
            Do you need to be installed in the shared location only, or in the user directory only,
            or can your module be installed anywhere?
            <hint>
            Installation location shall not matter, if it does explain why.
            Consider also whether <code>InstalledFileLocator</code> can help.
            </hint>
        </question>
-->
<answer id="deploy-shared">
Module can be installed anywhere.
</answer>


<!--
        <question id="exec-classloader" when="impl">
            Does your code create its own class loader(s)?
            <hint>
            A bit unusual. Please explain why and what for.
            </hint>
        </question>
-->
<answer id="exec-classloader">
No.
</answer>


<!--
        <question id="exec-component" when="impl">
            Is execution of your code influenced by any (string) property
            of any of your components?
            
            <hint>
            Often <code>JComponent.getClientProperty</code>, <code>Action.getValue</code>
            or <code>PropertyDescriptor.getValue</code>, etc. are used to influence
            a behavior of some code. This of course forms an interface that should
            be documented. Also if one depends on some interface that an object
            implements (<code>component instanceof Runnable</code>) that forms an
            API as well.
            </hint>
        </question>
-->
<answer id="exec-component">
    <api name="refreshSlow" category="private" type="export" group="property">
        One can ask FileObject.getAttribute("refreshSlow") and obtain an instance
        of <code>Runnable</code> with intricate behavior. This is a private contract
        used from core.ui module to show refresh progress and tested
        in <code>masterfs/test/unit/src/org/netbeans/modules/masterfs/SlowRefreshTest.java</code>.
    </api>
    <api name="org.netbeans.modules.masterfs.watcher.disable" category="private" type="export" group="systemproperty">
        It is possible to disable native listening on filesystem changes.
        Useful mostly in testing environment, but it may be interesting for some
        users too. Don't rely (much) on this property from production code however.
    </api>
    <api name="org.netbeans.modules.masterfs.watcher.FAM" category="private" type="export" group="systemproperty">
        It is possible to enable use of FAM notifier on Solaris disabled by default.
        Useful mostly in testing environment, but it may be interesting for some
        users too. Don't rely (much) on this property from production code however.
    </api>
</answer>


<!--
        <question id="exec-introspection" when="impl">
            Does your module use any kind of runtime type information (<code>instanceof</code>,
            work with <code>java.lang.Class</code>, etc.)?
            <hint>
            Check for cases when you have an object of type A and you also
            expect it to (possibly) be of type B and do some special action. That
            should be documented. The same applies on operations in meta-level
            (Class.isInstance(...), Class.isAssignableFrom(...), etc.).
            </hint>
        </question>
-->
<answer id="exec-introspection">
Naturally this module uses instanceof but I don't think its usage isn't suspicious or
worth of mentioning. 
</answer>


<!--
        <question id="exec-privateaccess" when="final">
            Are you aware of any other parts of the system calling some of 
            your methods by reflection?
            <hint>
            If so, describe the "contract" as an API. Likely private or friend one, but
            still API and consider rewrite of it.
            </hint>
        </question>
-->
<answer id="exec-privateaccess">
    <api category="friend" group="java" name="FileObjectMoveLookup" type="import">
    <code>BaseFileObj</code> implementation of <code>FileObject</code> is using
    a reflection to re-associate the lookup after a move operation. This is a 
    contract established with <code>openide.filesystems</code> module.
    </api>
</answer>


<!--
        <question id="exec-process" when="impl">
            Do you execute an external process from your module? How do you ensure
            that the result is the same on different platforms? Do you parse output?
            Do you depend on result code?
            <hint>
            If you feed an input, parse the output please declare that as an API.
            </hint>
        </question>
-->
<answer id="exec-process">
No.
</answer>


<!--
        <question id="exec-property" when="impl">
            Is execution of your code influenced by any environment or
            Java system (<code>System.getProperty</code>) property?
            
            <hint>
            If there is a property that can change the behavior of your 
            code, somebody will likely use it. You should describe what it does 
            and the <a href="http://openide.netbeans.org/tutorial/api-design.html#life">stability category</a>
            of this API. You may use
            <pre>
                &lt;api type="export" group="property" name="id" category="private" url="http://..."&gt;
                    description of the property, where it is used, what it influence, etc.
                &lt;/api&gt;            
            </pre>
            </hint>
        </question>
-->
<answer id="exec-property">
    <api name="org.netbeans.modules.masterfs.case" category="private" group="systemproperty" type="export">
    To address problems when mixing various types of network file systems 
    (as described in bug <code>198946</code>)
    there is a special property <code>org.netbeans.modules.masterfs.case</code>
    that can be set to <code>sensitive</code> or <code>insensitive</code> value
    in order to override the system default. This is intended only for end user
    consumption, not for consumption by other parts of the system. The name and
    meaning of this property may change in any release.
    </api>
    
    <api name="org.netbeans.io.suspend" category="devel" group="systemproperty" type="export">
        <p>
    Native listeners check the <code>org.netbeans.io.suspend</code> property. 
    If it is set to integer greater than zero, they stop delivering file change events.
    The list of modified directories is recorded (its size is made available
    by setting its string value into <code>org.netbeans.io.pending</code> property), 
    but its processing is suspended. Events are delivered when 
    <code>org.netbeans.io.suspend</code> property changes its value to <code>0</code>
    or becomes empty.
    </p>
    <p>
    I/O intensive operations in other NetBeans modules are advised
    to honour the <code>org.netbeans.io.suspend</code> property as well and
    suspend their I/O activities too.
    </p>
    <p>
    In order to properly communicate changes to the property between multiple
    <em>receivers</em> and multiple <em>controllers</em> it is suggested to
    only manipulate the value under <code>synchronized("org.netbeans.io.suspend".intern())</code>
    lock. Those changing the value are supposed to increment it by one when they
    request the suspend and decrement it by one when they want to resume their
    own suspend.
    </p>
    <p>
    Whenever a change to the state of the property is made,
    <em>controllers</em> are supposed to 
    <code>"org.netbeans.io.suspend".intern().notifyAll()</code>.
    </p>
    </api>
</answer>


<!--
        <question id="exec-reflection" when="impl">
            Does your code use Java Reflection to execute other code?
            <hint>
            This usually indicates a missing or insufficient API in the other
            part of the system. If the other side is not aware of your dependency
            this contract can be easily broken.
            </hint>
        </question>
-->
<answer id="exec-reflection">
No.
</answer>


<!--
        <question id="exec-threading" when="impl">
            What threading models, if any, does your module adhere to?
            <hint>
                If your module calls foreign APIs which have a specific threading model,
                indicate how you comply with the requirements for multithreaded access
                (synchronization, mutexes, etc.) applicable to those APIs.
                If your module defines any APIs, or has complex internal structures
                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.
                Examples: a class might be non-thread-safe (like Java Collections); might
                be fully thread-safe (internal locking); might require access through a mutex
                (and may or may not automatically acquire that mutex on behalf of a client method);
                might be able to run only in the event queue; etc.
                Also describe when any events are fired: synchronously, asynchronously, etc.
                Ideas: <a href="http://core.netbeans.org/proposals/threading/index.html#recommendations">Threading Recommendations</a> (in progress)
            </hint>
        </question>
-->
<answer id="exec-threading">
Supposed to be thread-safe - complex fine-grained locking. Relies on Filesystems thread semantics.
</answer>


<!--
        <question id="format-clipboard" when="impl">
            Which data flavors (if any) does your code read from or insert to
            the clipboard (by access to clipboard on means calling methods on <code>java.awt.datatransfer.Transferable</code>?
            
            <hint>
            Often Node's deal with clipboard by usage of <code>Node.clipboardCopy, Node.clipboardCut and Node.pasteTypes</code>.
            Check your code for overriding these methods.
            </hint>
        </question>
-->
<answer id="format-clipboard">
No.
</answer>


<!--
        <question id="format-dnd" when="impl">
            Which protocols (if any) does your code understand during Drag &amp; Drop?
            <hint>
            Often Node's deal with clipboard by usage of <code>Node.drag, Node.getDropType</code>. 
            Check your code for overriding these methods. Btw. if they are not overridden, they
            by default delegate to <code>Node.clipboardCopy, Node.clipboardCut and Node.pasteTypes</code>.
            </hint>
        </question>
-->
<answer id="format-dnd">
No.
</answer>


<!--
        <question id="format-types" when="impl">
            Which protocols and file formats (if any) does your module read or write on disk,
            or transmit or receive over the network?
        </question>
-->
<answer id="format-types">
No.
</answer>


<!--
        <question id="lookup-lookup" when="init">
            Does your module use <code>org.openide.util.Lookup</code>
            or any similar technology to find any components to communicate with? Which ones?
            
            <hint>
            Please describe the interfaces you are searching for, where 
            are defined, whether you are searching for just one or more of them,
            if the order is important, etc. Also classify the stability of such
            API contract.
            </hint>
        </question>
-->
<answer id="lookup-lookup">
All registered <code>FileSystemProvider</code> and <code>AutoMountProvider</code>
instances are queried and used. 
</answer>


<!--
        <question id="lookup-register" when="final">
            Do you register anything into lookup for other code to find?
            <hint>
            Do you register using layer file or using <code>META-INF/services</code>?
            Who is supposed to find your component?
            </hint>
        </question>
-->
<answer id="lookup-register">
URLMapper implementation is registered using <code>META-INF/services</code>. URLMapper
is supposed to find it (may sound strange but in filesystems isn't separated API, SPI
and implementation). 
</answer>


<!--
        <question id="lookup-remove" when="final">
            Do you remove entries of other modules from lookup?
            <hint>
            Why? Of course, that is possible, but it can be dangerous. Is the module
            your are masking resource from aware of what you are doing?
            </hint>
        </question>
-->
<answer id="lookup-remove">
No.
</answer>


<!--
        <question id="perf-exit" when="final">
            Does your module run any code on exit?
        </question>
-->
<answer id="perf-exit">
No.
</answer>


<!--
        <question id="perf-huge_dialogs" when="final">
            Does your module contain any dialogs or wizards with a large number of
            GUI controls such as combo boxes, lists, trees, or text areas?
        </question>
-->
<answer id="perf-huge_dialogs">
No.
</answer>


<!--
        <question id="perf-limit" when="init">
            Are there any hard-coded or practical limits in the number or size of
            elements your code can handle?
        </question>
-->
<answer id="perf-limit">
No hard-coded limits. Practical limit of registered instances of <code>AutoMountProvider</code> 
depends on performance meassurement.
</answer>


<!--
        <question id="perf-mem" when="final">
            How much memory does your component consume? Estimate
            with a relation to the number of windows, etc.
        </question>
-->
<answer id="perf-mem">
Memory occupation varies widely - the more FileObjects are requested the higher memory
consumption. 
</answer>


<!--
        <question id="perf-menus" when="final">
            Does your module use dynamically updated context menus, or
            context-sensitive actions with complicated enablement logic?
        </question>
-->
<answer id="perf-menus">
No.
</answer>


<!--
        <question id="perf-progress" when="final">
            Does your module execute any long-running tasks?
            
            <hint>Long running tasks should never block 
            AWT thread as it badly hurts the UI
            <a href="http://performance.netbeans.org/responsiveness/issues.html">
            responsiveness</a>.
            Tasks like connecting over
            network, computing huge amount of data, compilation
            be done asynchronously (for example
            using <code>RequestProcessor</code>), definitively it should 
            not block AWT thread.
            </hint>
        </question>
-->
<answer id="perf-progress">
Mounting new FileSystem could be considered long-running task under some circumstances.
Cache with living FileObjects must be traversed and delegates are changed if necessary.
</answer>


<!--
        <question id="perf-scale" when="init">
            Which external criteria influence the performance of your
            program (size of file in editor, number of files in menu, 
            in source directory, etc.) and how well your code scales?
            <hint>
            Please include some estimates, there are other more detailed 
            questions to answer in later phases of implementation. 
            </hint>
        </question>
-->
<answer id="perf-scale">
The higher number of registered instances of <code>AutoMountProvider</code> and
the higher number of mounted filesystems then more negatively affected
performance.
</answer>


<!--
        <question id="perf-spi" when="init">
            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
            do you enforce, that it will behave correctly and fast and will not
            negatively influence the performance of your own module?
            </hint>
        </question>
-->
<answer id="perf-spi">
No enforcement.
</answer>


<!--
        <question id="perf-startup" when="final">
            Does your module run any code on startup?
        </question>
-->
<answer id="perf-startup">
MasterFileSystem is just instantiated by <code>AutomountSupport</code>code>.
</answer>


<!--
        <question id="perf-wakeup" when="final">
            Does any piece of your code wake up periodically and do something
            even when the system is otherwise idle (no user interaction)?
        </question>
-->
<answer id="perf-wakeup">
No polling.
</answer>


<!--
        <question id="resources-file" when="final">
            Does your module use <code>java.io.File</code> directly?
            
            <hint>
            NetBeans provide a logical wrapper over plain files called 
            <code>org.openide.filesystems.FileObject</code> that
            provides uniform access to such resources and is the preferred
            way that should be used. But of course there can be situations when
            this is not suitable.
            </hint>
        </question>
-->
<answer id="resources-file">
Yes, this module provides implementation of FileSystem addresing resources accessible by java.io.File.
</answer>


<!--
        <question id="resources-layer" when="final">
            Does your module provide own layer? Does it create any files or
            folders in it? What it is trying to communicate by that and with which 
            components?
            
            <hint>
            NetBeans allows automatic and declarative installation of resources 
            by module layers. Module register files into appropriate places
            and other components use that information to perform their task
            (build menu, toolbar, window layout, list of templates, set of
            options, etc.). 
            </hint>
        </question>
-->
<answer id="resources-layer">
Yes, MasterFileSystem is automaticaly mounted into Repository via its registration 
in /Mount folder in mf-layer.
</answer>


<!--
        <question id="resources-mask" when="final">
            Does your module mask/hide/override any resources provided by other modules in
            their layers?
            
            <hint>
            If you mask a file provided by another module, you probably depend
            on that and do not want the other module to (for example) change
            the file's name. That module shall thus make that file available as an API
            of some stability category.
            </hint>
        </question>
-->
<answer id="resources-mask">
No.
</answer>


<!--
        <question id="resources-read" when="final">
            Does your module read any resources from layers? For what purpose?
            
            <hint>
            As this is some kind of intermodule dependency, it is a kind of API.
            Please describe it and classify according to 
            <a href="http://openide.netbeans.org/tutorial/api-design.html#categories">
            common stability categories</a>.
            </hint>
        </question>
-->
<answer id="resources-read">
No hidden intermodule dependency.
</answer>

</api-answers>