Re[2]: Add posibility to add custom ModuleReaderFactory to ModuleFinder

[Alex Sviridov]

Hi Alan

Thank you for your answer. But my main problem is not jars inside .war - this is a so far from my current problem. Now I need to 1) add .war file to layer 2). to map file location, for example instead of "module-info.java" I must find "WEB-INF/classes/module-info.java" etc. That is all I need. How can I do it without implementing ModuleFinder?

Best regards, Pavel


>Пятница, 28 сентября 2018, 15:03 +03:00 от Alan Bateman <Alan.Bateman at oracle.com>:
>
>On 28/09/2018 10:01, Alex Sviridov wrote:
>>  From java 9 we can create JPMS layers and dynamically add modules to it. At the same time different types of java archives can be JPMS modules - .jar, .war, .ear. However, the problem is that it is possible to add only .jar archives by default. I opened an issue here   https://bugs.openjdk.java.net/browse/JDK-8203330  and as it was found out it is necessary to implement custom ModuleFinder.
>>
>> Trying to implement ModuleFinder I understood that it is necessary to rewrite (or take from) the "half" of jdk.intenal what is a very bad way.
>>
>> Lets' consider what I need to add .war arhives to JPMS layer. I need: 1) to understand if I can work with this type of archive or I can not (if .war is supported) 2). to map file location, for example instead of "module-info.java" I must find "WEB-INF/classes/module-info.java" etc. For that I don't need to create ModuleDescriptor, ModuleReference, ModuleFinder.
>>
>> So I suggest to overload ModuleFinder.of() method adding as a parameter custom ModuleReaderFactory. For example to add ModuleFinder#of(ModuleReaderFactory factory, Path... entries). ModuleReaderFactory must have such method - createModuleReader(Path path). Such solution will also help Jakarta EE developers a lot of.
>>
>Creating a ModuleFinder that can find modules in WAR files shouldn't 
>need any API additions or copying of code from the JDK. Where are the 
>pain points that you are running into? Is it because a WAR files is 
>single artifact that may contain several modules (the application module 
>under WEB-INF/classes and dependences are packaged as JAR files under 
>WEB-INF/lib). One thing to be aware of is that the zip file system 
>provider was updated recently to improve its support for opening JAR 
>files in custom file systems, this means you can do things like this:
>
>         ClassLoader scl = ClassLoader.getSystemClassLoader();
>         try (FileSystem warfs = FileSystems.newFileSystem(war, scl)) {
>             Path classes = warfs.getPath("/WEB-INF/classes");
>             Files.walk(classes)
>                     .map(p -> classes.relativize(p))
>                     .forEach(System.out::println);
>
>             Path lib = warfs.getPath("WEB-INF/lib");
>             Files.find(lib, 1, (path, attrs) -> 
>path.toString().endsWith("jar"))
>                     .forEach(jar -> {
>                         try (FileSystem jarfs = 
>FileSystems.newFileSystem(jar, scl)) {
>                             Path top = jarfs.getPath("/");
>                             Files.walk(top)
>                                     .map(p -> top.relativize(p))
>                                     .forEach(System.out::println);
>                         } catch (IOException ioe) {
>                             throw new UncheckedIOException(ioe);
>                         }
>                     });
>         }
>
>Another thing to be aware of is that the ModuleFinder.of(Path[]) can 
>also deal with JAR files that are packaged inside other JAR files. It 
>does have to extract them to a temporary location on the file system and 
>there may several potential improvements that could be just, just hasn't 
>been an area to spend time on.
>
>-Alan.
>
>
>


-- 
Alex Sviridov