One problem is that frameworks like Spring Boot need to scan the classes that are available in a module, to get a list of the names of all the classes, among other things. The JDK provides no standard way to do that. For example, how would you implement a class like this one?
https://github.com/spring-projects/spring-boot/blob/master/spring-boot-project/spring-boot-tools/spring-boot-loader-tools/src/main/java/org/springframework/boot/loader/tools/MainClassFinder.java Samuel On Sat, Oct 9, 2021, 10:21 Ioi Lam <ioi....@oracle.com> wrote: > As a proof of concept, I wrote a quick-and-dirty demo that can load > Jigsaw modules from a Uber-JAR file: > > https://github.com/iklam/tools/tree/main/jigsaw/uberjar > > Glavo, would something like this fit your needs? > > I think something like this could be done outside the JDK (in frameworks > like SpringBoot) or inside the JDK (as some sort of extension to "java > -jar", for example). > > As the demo shows, we already have the core API support to enable this. > I would encourage other member of the Java community to experiment with > it and see if we should proceed further in this direction. > > Thanks > - Ioi > > On 10/7/21 9:31 PM, Ioi Lam wrote: > > I am wondering if there are 3rd party solutions that support loading > > Jigsaw modules from uber jars. The JDK should have all the APIs to > > support such a solution. > > > > E.g., I looked at SpringBoot, which has uber jar support, but it > > doesn't seem to support modules ("java.lang.module" doesn't appear in > > any of the source files). > > > > Thanks > > - Ioi > > > > On 10/7/21 6:43 AM, Gregg Wonderly wrote: > >> The URL class loader is the easiest way to solve conditional > >> loading. In Jini, now Apache River, we’ve long used this mechanism > >> to “get” the implementation of all interfaces that a remote client > >> application needed to talk to a particular server (versioning makes > >> this necessary and powerfully easy as a solution). But the security > >> manager didn’t seem useful as of late and the removal of the security > >> manager support for managing per jar security is a bit problematic > >> for this kind of mobile code use in Java. Yet, this is the primary > >> way that javascript works in the web browser as the mobile code > >> interface to remote services. It really feels like Oracle and the > >> Java team have no interest in what the desktop environment represents… > >> > >> Gregg Wonderly > >> > >>> On Oct 7, 2021, at 7:41 AM, Glavo <zjx001...@gmail.com> wrote: > >>> > >>>> *Bandwidth optimization and rare machines.* This is interesting > >>>> because > >>>> it's a requirement that feels like it may be more common in China than > >>>> elsewhere. I'd be keen to learn more about your bandwidth constraints, > >>>> unless this is more of a theoretical concern? > >>> > >>> Ah, in fact, in Chinese mainland, server bandwidth is a very real > >>> problem. In China, many websites such as GitHub and cloudflare cannot > >>> provide services normally. The cost of civil broadband is low, but > >>> commercial bandwidth is more expensive, which costs several times or > >>> even more than ten times higher than other parts of the world. > >>> Our average income level also lags behind that of developed countries, > >>> so we will pay more attention to the cost of bandwidth. > >>> > >>> Mike Hearn <m...@plan99.net> 于2021年10月7日周四 下午7:31写道： > >>> > >>>> Thanks for your insightful reply, Glavo. Here are some thoughts. I > >>>> should > >>>> note that I don't work for Oracle or on OpenJDK, in case that wasn't > >>>> already clear. > >>>> > >>>> *Forum.* Although it's logical that you ended up on this list, > >>>> realistically the JPMS is "done" and not being worked on since Java > >>>> 9. Any > >>>> solutions or improvements have to come from the user community so > >>>> it may > >>>> make more sense to have this discussion on Reddit, or some other > >>>> Java forum. > >>>> > >>>> *Alternative approach. *Given this constraint, it can make sense to > >>>> think > >>>> wider or bigger than just updating previous approaches. Would your > >>>> needs be > >>>> met or even met better by a re-imagining of Web Start, but one > >>>> suitable for > >>>> servers and the CLI? For example: > >>>> > >>>> $ alias glavos="jrun glavos-cool-app.com" > >>>> $ glavos --flag --another-flag > >>>> > >>>> Here an imaginary "jrun" command (re)downloads an app and stores it > >>>> to a > >>>> local cache, perhaps downloading an appropriate JVM/jlinked image > >>>> alongside > >>>> it if none is available already locally. It's given a URL but in a > >>>> convenient form for typing, e.g. with assumed protocols and paths > >>>> if only a > >>>> domain name is specified. The tool would occasionally check for > >>>> updates and > >>>> run from the cache the rest of the time. This doesn't make apps into a > >>>> single file but it tackles other problems you mention having to > >>>> roll your > >>>> own solutions for, like writing your own update checker and asking > >>>> users to > >>>> download the right file. Unlike tools like apt-get or brew there > >>>> would be > >>>> no notion of adding a repository beforehand, so for CLI / server > >>>> apps, it > >>>> retains its usability. > >>>> > >>>> For desktop apps a simple .jrun file association could be used to > >>>> do the > >>>> same thing. > >>>> > >>>> For building Docker images you could have: > >>>> > >>>> $ jrun --cache-only glavos-cool-app.com > >>>> > >>>> which would populate a cache during the docker build, but not run the > >>>> program itself. > >>>> > >>>> I've often wished for such a tool. At one point I built one that > >>>> did Maven > >>>> resolution, but it for GUI apps. Although my new venture is about > >>>> self-updating desktop/server app packages, I've been planning an > >>>> extension > >>>> in this direction later because once you can distribute a generic > >>>> runtime > >>>> as a self-updating "app" you can easily bring back the JRE model > >>>> for those > >>>> who want it. > >>>> > >>>> *Jimage.* In your first mail you proposed a new kind of fat-jar > >>>> based on > >>>> the jimage format the modules file uses. JImage isn't a documented > >>>> format, > >>>> or rather, it's documented only in the source code, but it has quite a > >>>> clever design. The upside is that it's highly optimized. The > >>>> downsides are: > >>>> > >>>> 1. Write only. ZIPs have some basic support for editing but jimage > >>>> doesn't. This is a pain for things like config files, where you may > >>>> want to > >>>> make specialized versions of an app by adjusting the internal > >>>> files. It can > >>>> be easily fixed using a classloader that checks local disk for > >>>> resources > >>>> first. > >>>> > >>>> 2. No built-in support for native code libraries. There was a related > >>>> discussion of this problem a week or so ago on this list. Of > >>>> course, JARs > >>>> have the same problem. > >>>> > >>>> 3. No support for multiple versions of the same JAR in the same > >>>> file, even > >>>> though the core JPMS *can* support this via the > >>>> defineModulesWithManyLoaders API, and even though this would be a very > >>>> useful thing to support. Fat JARs have the same problem so this is > >>>> not a > >>>> downside compared to the status quo. > >>>> > >>>> 4. The format is deliberately undocumented so it can be changed in > >>>> future > >>>> JVM versions. Thus using it would actually mean cloning it, and/or > >>>> rewriting parts of the code because otherwise the GPL2 might kick in. > >>>> > >>>> Overall, the downsides are not that big! The worst is the need to > >>>> clone > >>>> the format to avoid depending on JVM internals. On the other hand, > >>>> ZIPs > >>>> work well enough and don't require writing any new code except a > >>>> little > >>>> stub entry point that uses custom classloaders. > >>>> > >>>> *Bandwidth optimization and rare machines.* This is interesting > >>>> because > >>>> it's a requirement that feels like it may be more common in China than > >>>> elsewhere. I'd be keen to learn more about your bandwidth constraints, > >>>> unless this is more of a theoretical concern? > >>>> > >>>> You mention you actually have users on LoongArch64 for example. > >>>> Indeed, > >>>> the chances that non-Chinese developers will produce jlinked images > >>>> for > >>>> this CPU any time soon is very low. > >>>> > >>>> *Product potential.* As mentioned, I'm setting up a new venture > >>>> that is > >>>> starting with app distribution, and particularly distribution for > >>>> the JVM > >>>> world. JPackage is good as far as it goes, but it doesn't solve all > >>>> the > >>>> problems developers face. Given your list of target machines it > >>>> feels like > >>>> you're probably a commercial organization with a wide customer > >>>> base. If > >>>> you're in the market for better approaches please send an email to > >>>> mike@hydraulic.software and maybe your needs can influence our > product > >>>> direction. > >>>> > >>>> > >>>> > > > >
