| = GEP-6: NIO2 Support for Groovy |
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| :icons: font |
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| .Metadata |
| **** |
| [horizontal,options="compact"] |
| *Number*:: GEP-6 |
| *Title*:: NIO2 Support for Groovy |
| *Version*:: 2 |
| *Type*:: Feature |
| *Status*:: Final |
| *Comment*:: Delivered in Groovy 2.3 |
| *Leader*:: Merlyn Albery-Speyer/Hamlet D'Arcy |
| *Created*:: 2010-09-25 |
| *Last modification* :: 2018-10-12 |
| **** |
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| == Abstract |
| |
| JDK 7 includes a new java.nio.file package and Path class. |
| These provide extended capabilities for filesystem tasks. |
| We should explore incorporation into Groovy. |
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| == Approach |
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| I propose: |
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| * Create an openjdk7 build of Groovy |
| * Move NIO2 support to a Groovy Module for now |
| * Move NIO2 Groovy Module to Groovy-core when JDK7 is officially released |
| |
| JDK7 is still in beta. It is subject to change. If we build NIO2 support into Groovy today and make a release, |
| then we risk having JDK7 make an API change, which would force us to support 2 different APIs. That would be bad. |
| |
| === Todo in Groovy NIO Module: |
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| * Support new Path object |
| * All of the GDK File API needs to be on Path |
| * NIO2 contains a new WatchService API. We need to probably provide a GDK on WatchService to make it easy to work |
| with using closures, etc. This is the most interesting piece of work IMO. |
| |
| === Todo in Groovy Core: |
| |
| Groovy has a FileNameFinder and FileNameRegExFinder. This stuff needs to work with Paths as well: |
| http://mrhaki.blogspot.com/2009/11/groovy-goodness-finding-files-with.html |
| |
| I haven't looked at each file in this list yet, but we need to analyze these Groovy source files and see if |
| any parallel Path implementations are needed. The first 3 files look like the most important: |
| |
| ``` |
| ./groovy/util/IFileNameFinder.java |
| ./groovy/io/FileType.java |
| ./groovy/io/FileVisitResult.java |
| ./org/codehaus/groovy/runtime/WritableFile.java |
| ./org/codehaus/groovy/ant/FileIterator.java |
| ./org/codehaus/groovy/ant/FileScanner.java |
| ./org/codehaus/groovy/control/io/FileReaderSource.java |
| ``` |
| |
| I couldn't find any instances of this in Groovy-core, but any `asType(File)` methods need a parallel |
| `asType(Path)` - I believe `asWritable(Path)` is the only change required. In NIO2, I believe `File.list` |
| and another method now return an iterator, which enables this method to work better over networks. |
| We need to update the File GDK to use this approach by default to also support network dir or ls style listings. |
| NIO2 has a new `FileVisitor` class. We need to unify this new `FileVisitor` JDK method with what Groovy does |
| today in with GDK with the `.eachFile` method. As well as the `.eachFileXXX` methods and the `.eachDirXXX` |
| methods we should include the `.traverse` method when looking through potential places for unification. |
| The `.traverse` method's primary role was to make some `FileVisitor` like functionality available in the pre-JDK 7 |
| world but having NIO2 there might open up some more possibilities. There was also some thought at the time of having |
| additional overloaded traverse methods with a more statically typed flavor rather than just the current Map solution. |
| I guess now is a good time to also look at that option. |
| |
| == References and useful links |
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| === Mailing-list discussions |
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| * https://markmail.org/thread/osst6q4obk56fxqg[groovy-dev: OpenJDK 7 Groovy Build and NIO2 support] |
| * https://docs.oracle.com/javase/8/docs/technotes/guides/io/index.html[Java I/O, NIO and NIO.2] |
| |
| === JIRA issues |
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| * https://issues.apache.org/jira/browse/GROOVY-4390[GROOVY-4390: Add GDK File methods to the NIO2 API] |
| * https://issues.apache.org/jira/browse/GROOVY-4391[GROOVY-4391: Groovy build fails test target using Java 1.7.0] |
| |
| == Update history |
| |
| 1 (2010-02-16):: Version as extracted from Codehaus wiki |
| 2 (2018-10-14):: Numerous minor tweaks |
