NetBeans Architecture Answers for File System API module

General Information

Question (arch-what): What is this project good for?
Answer: The Filesystems API provides a common API to access files in a uniform manner. It is available as standalone library and also is bundled together with other parts of the openide. Specification
Question (arch-overall): Describe the overall architecture.
Answer:

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.

Question (arch-usecases): Describe the main use cases of the new API. Who will use it under what circumstances? What kind of code would typically need to be written to use the module?
Answer:

For general overview of the filesystem concepts, related topics, together with code samples, see chapter 3, of NetBeans Platform for Beginners by Jason Wexbridge and Walter Nyland. Many of the usecases are described at the overall documentation, in a way how to register a mime type. Some of the additional usecases are covered here.

How to change menus, etc. after login?

See documentation about dynamically changing the system filesystem.

Question (arch-time): What are the time estimates of the work?
Answer:

XXX no answer for arch-time

Question (arch-quality): How will the quality of your code be tested and how are future regressions going to be prevented?
Answer:

XXX no answer for arch-quality

Question (arch-where): Where one can find sources for your module?
Answer:

The sources for the module are in the Apache Git repositories or in the GitHub repositories

Project and platform dependencies

Question (dep-nb): What other NetBeans projects and modules does this one depend on?
Answer:
• UtilitiesAPI
• LookupAPI

The default answer to this question is:


These modules are required in project.xml:

• WeakListener.setAccessible - The module is needed for compilation. The module is used during runtime. Specification version 9.20 is required.
• LookupAPI - The module is needed for compilation. The module is used during runtime. Specification version 8.17 is required.
• UtilitiesAPI - The module is needed for compilation. The module is used during runtime. Specification version 9.36 is required.
Question (dep-non-nb): What other projects outside NetBeans does this one depend on?
Answer: SAX parser is used to parse layers and attributes in .nbattrs files.
Question (dep-platform): On which platforms does your module run? Does it run in the same way on each?
Answer: Platform independent. But filesystem impl. on OS must satisfy usual naming conventions.
Question (dep-jre): Which version of JRE do you need (1.2, 1.3, 1.4, etc.)?
Answer: JRE 1.3.
Question (dep-jrejdk): Do you require the JDK or is the JRE enough?
Answer: JRE is enough.

Deployment

Question (deploy-jar): Do you deploy just module JAR file(s) or other files as well?
Answer: Filesystems API and SPI is part of openide.jar.
Question (deploy-nbm): Can you deploy an NBM via the Update Center?
Answer: Yes (openide.nbm).
Question (deploy-shared): Do you need to be installed in the shared location only, or in the user directory only, or can your module be installed anywhere?
Answer: As part of openide.jar needs to be in the system directory.
Question (deploy-packages): Are packages of your module made inaccessible by not declaring them public?
Answer: No.
Question (deploy-dependencies): What do other modules need to do to declare a dependency on this one, in addition to or instead of the normal module dependency declaration (e.g. tokens to require)?
Answer:

XXX no answer for deploy-dependencies

Compatibility with environment

Question (compat-i18n): Is your module correctly internationalized?
Answer: Yes.
Question (compat-standards): Does the module implement or define any standards? Is the implementation exact or does it deviate somehow?
Answer: It defines and implements the FilesystemsAPI
Question (compat-version): 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?
Answer: Yes.
Question (compat-deprecation): How the introduction of your project influences functionality provided by previous version of the product?
Answer:

XXX no answer for compat-deprecation

Access to resources

Question (resources-file): Does your module use java.io.File directly?
Answer: Yes, naturally.
Question (resources-layer): 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?
Answer: No.
Question (resources-read): Does your module read any resources from layers? For what purpose?
Answer: No.
Question (resources-mask): Does your module mask/hide/override any resources provided by other modules in their layers?
Answer: No.
Question (resources-preferences): Does your module uses preferences via Preferences API? Does your module use NbPreferences or or regular JDK Preferences ? Does it read, write or both ? Does it share preferences with other modules ? If so, then why ?
Answer:

FileChooserBuilder uses NbPreferences as the backing storage for per-key recently used directories.

Lookup of components

Question (lookup-lookup): Does your module use org.openide.util.Lookup or any similar technology to find any components to communicate with? Which ones?
Answer: The following services are looked up:
• Implementations of MIMEResolver and URLMapper are looked up
• instance of FileSystem.Status which is used as the Status of the default FileSystem
• instance of CustomInstanceFactory which is used to create instances for FileSystem files without instanceCreate attribute
Question (lookup-register): Do you register anything into lookup for other code to find?
Answer: URLStreamHandlerFactory implementations for nbfs: and memory: protocols are registered as named services.
Question (lookup-remove): Do you remove entries of other modules from lookup?
Answer: No.

Execution Environment

Question (exec-property): Is execution of your code influenced by any environment or Java system (System.getProperty) property? On a similar note, is there something interesting that you pass to java.util.logging.Logger? Or do you observe what others log?
Answer:
• org.openide.filesystems.DefaultAttributes.ATTR_NAME_EXT_XML - Name of attribute file can be changed , if .nbattrs can't be used.
• netbeans.debug.heap - Periodic refresh can be blocked.
• org.openide.filesystems.LocalFileSystem.REFRESH_TIME - Periodic refresh can be set.
• org.openide.filesystems.annotateUnclosedStreams -

  If true, better diagnostic information will be available as to when file input or output streams were opened that prevent a file from being deleted because they were not closed. This information comes at a performance cost, however.

• allow.filechooser.symlink.traversal - Used by FileChooserBuilder. If set to false, file choosers created by instances of FileChooserBuilder will traverse symlinks. By default they do not. forget.recent.dirs - Used by FileChooserBuilder. If true, FileChooserBuilder will not remember users' recent directories across sessions. This property is provided for applications where a history of recently used directories is a security concern.
Question (exec-component): Is execution of your code influenced by any (string) property of any of your components?
Answer: fallback -

See documentation of FileSystem.

revealEntries -

The MultiFileSystem defines some pseudo attributes on files and folders, which provide rollback features. Please see MultiFileSystem class javadoc for more information.

Question (exec-ant-tasks): Do you define or register any ant tasks that other can use?
Answer:

XXX no answer for exec-ant-tasks

Question (exec-classloader): Does your code create its own class loader(s)?
Answer: No.
Question (exec-reflection): Does your code use Java Reflection to execute other code?
Answer: methodvalue-newvalue - When special form of setAttribute is supported by the filesystem, the getAttribute can behave like XMLFileSystem's methodvalue and newvalue attributes:
• "-//NetBeans//DTD DefaultAttributes 1.0//EN"
• "-//NetBeans//DTD Filesystem 1.0//EN"
raw-value - It is possible to prefix call to FileObject.getAttribute with raw: prefix to evaluate the attribute without instantiating it (e.g. get Method or Class values from methodvalue and newvalue attributes. This API is not intended for public use at present and can change in future.
Question (exec-privateaccess): Are you aware of any other parts of the system calling some of your methods by reflection?
Answer: FileObjectMoveLookup - masterfs module is using a reflection to re-associate the lookup after a move operation.
Question (exec-process): 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?
Answer: No external process.
Question (exec-introspection): Does your module use any kind of runtime type information (instanceof, work with java.lang.Class, etc.)?
Answer: No answer
Question (exec-threading): What threading models, if any, does your module adhere to? How the project behaves with respect to threading?
Answer:

XXX no answer for exec-threading

Question (security-policy): Does your functionality require modifications to the standard policy file?
Answer:

XXX no answer for security-policy

Question (security-grant): Does your code grant additional rights to some other code?
Answer:

XXX no answer for security-grant

Format of files and protocols

Question (format-types): Which protocols and file formats (if any) does your module read or write on disk, or transmit or receive over the network? Do you generate an ant build script? Can it be edited and modified?
Answer:
• attributes-1_0.dtd - -//NetBeans//DTD DefaultAttributes 1.0//EN
• filesystem-1_0.dtd - -//NetBeans//DTD Filesystem 1.0//EN
Question (format-dnd): Which protocols (if any) does your code understand during Drag & Drop?
Answer: None.
Question (format-clipboard): Which data flavors (if any) does your code read from or insert to the clipboard (by access to clipboard on means calling methods on java.awt.datatransfer.Transferable?
Answer: None.

Performance and Scalability

Question (perf-startup): Does your module run any code on startup?
Answer: No.
Question (perf-exit): Does your module run any code on exit?
Answer: No.
Question (perf-scale): 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?
Answer: As far as I know the code scales linearily.
Question (perf-limit): Are there any hard-coded or practical limits in the number or size of elements your code can handle?
Answer: No.
Question (perf-mem): How much memory does your component consume? Estimate with a relation to the number of windows, etc.
Answer: Hardly to estimate, depends on many factors. Instances of FileObject can be kept weak or hard, implementatins of FileObject may differ each other. Approximately for FileObject that comes from AbstractFileSystem impl. probably 100 B if size of name is average .
Question (perf-wakeup): Does any piece of your code wake up periodically and do something even when the system is otherwise idle (no user interaction)?
Answer: No. Periodic refresh is disabled at the moment as default.
Question (perf-progress): Does your module execute any long-running tasks?
Answer: There are no such long running tasks except refresh operation, that may be time consuming. Naturally also operations on FileSystem, that access remote files over network.
Question (perf-huge_dialogs): Does your module contain any dialogs or wizards with a large number of GUI controls such as combo boxes, lists, trees, or text areas?
Answer: No.
Question (perf-menus): Does your module use dynamically updated context menus, or context-sensitive actions with complicated and slow enablement logic?
Answer: No.
Question (perf-spi): How the performance of the plugged in code will be enforced?
Answer:

XXX no answer for perf-spi