Re: How to do “--add-modules” with dynamically created layer in JPMS?
On 16/11/2020 09:17, Alex Orlov wrote:
Hello Alan,
Thank you for such detailed answer. I read it with attention, but
still don’t know how to solve my situation.
Maybe may question didn’t provide all details, so here they are.
I want to create the following layer structure:
+++
+ Boot Layer +
+++
|
+
+ Web Server Layer +
+
|
+ Web Application Layer +
So, we have always one boot layer (it’s clear), one web server layer,
and multiple web application layers. At
the same time all web application layers have one parent — web server
layer. Boot layer doesn’t know and mustn’t know
about any child layer modules So it is impossible to add all
modules to boot layer!
In web server layer I have servlet container (Jetty) and rest
implementation (Jersey). When I create web server layer
Configuration cf =
parentLayer.configuration().resolveAndBind(moduleFinder,
ModuleFinder.of(), moduleNames);
ModuleLayer layer = parentLayer.defineModulesWithOneLoader(cf,
parentClassLoader);
I add to it all modules of jetty, jersey and their dependencies. At
the same time jetty knows nothing about jersey. When web server layer
is created one of its modules starts Jetty.
So, when does jersey start? It starts only when web application layer
is created with .war file that has web.xml with jersey servlet. For
example:
JerseyServlet
org.glassfish.jersey.servlet.ServletContainer
So, in such configuration, when web server layer is created no one can
know if jersey will be used.
What what does JPMS do? It ignores all jersey modules including all
its dependencies (including API). So, the question.
How to ask JPMS not to ignore modules that it must add to layer?
Thanks for the diagram, and names, of the module layers.
If I read your mail correctly then you are saying that the Jersey module
is observable when you create the configuration for "Web Server Layer".
It is not resolved because it's not in the set of root modules that you
specify to resolveAndBind. It is also not required by any of the modules
that end up in the configuration. This should not be a surprise. If the
intention for "Web Server Layer" to contain Jersey and other modules
that web applications may need then you will need to add them to the set
of root modules ("moduleNames" in your code fragment. If the modules are
completely unrelated then you might want to scan them so that
"moduleNames" has the names of the modules that export an API.
Does the .war file containing "JerseyServlet" have a module-info.class?
I'm curious if it declares "requires Jersey" as I would expect that the
resolve or resolveAndBind for the web application will fail if it
requires Jersey and it is not observable or is not in the parent layer.
-Alan
Re: How to do “--add-modules” with dynamically created layer in JPMS?
On 15/11/2020 19:16, Alex Orlov wrote: Hi all, I create JPMS layer this way: Configuration cf = parentLayer.configuration().resolveAndBind(moduleFinder, ModuleFinder.of(), moduleNames); ModuleLayer layer = parentLayer.defineModulesWithOneLoader(cf, parentClassLoader); And I have a problem with adding implementation modules. These implementation modules are ignored by JPMS because classes from these modules are not used anywhere (it is clear, that classes from API modules are used). So, JPMS doesn't add these modules to layer. As I understand, if I spoke about implementation modules on boot layer, I could use --add-modules jvm argument. However, I couldn't find any information how to force JPMS load my module (even if its classes are not used) for dynamically created layers. Could anyone say how to do it? It would be useful if you could give an example of "implementation module". I can't tell if you mean a jdk.* module, a service provider module that doesn't export an API, or something else. In any case, I think the picture you are describing is a module that is observable, either in the run-time image or on module path. The module is not resolved at startup (and so is not in the boot layer) because the initial module that you specify with `java -m` doesn't transitively require it and it doesn't provide an implementation of a service that any of the other resolved modules use. The summary is a module layer is immutable and there isn't any way to add modules to a module layer once it has been created. For what you are doing then maybe `--add-modules ALL-SYSTEM` can be used as workaround. This will ensure that all system/platform modules are in the boot layer as these modules cannot be loaded into a child layer (Johannes's suggest to specify the module name to resolveAndBind will not work for java.* modules as they cannot be loaded into child layers, his suggestion may work for other modules). One other point to mention is that the original set of requirement envisaged some means to augment the set of platform modules at run-time. We didn't get to that requirement except for the limited scenario that is tools loading the JMX agent or a java agent into a running VM. These limited scenario involve loading the jdk.management.agent or java.instrument modules and that is some with a special child layer rather than augmenting the boot layer. This partial solution, along with `--add-modules ALL-SYSTEM`as a workaround for the general cases, has been sufficient to date. -Alan
Re: How to do “--add-modules” with dynamically created layer in JPMS?
I think you need to specify the "implementation modules" in the last argument of Configuration.resolveAndBind(...). Best regards, Johannes Am 15.11.2020 um 20:16 schrieb Alex Orlov: Hi all, I create JPMS layer this way: Configuration cf = parentLayer.configuration().resolveAndBind(moduleFinder, ModuleFinder.of(), moduleNames); ModuleLayer layer = parentLayer.defineModulesWithOneLoader(cf, parentClassLoader); And I have a problem with adding implementation modules. These implementation modules are ignored by JPMS because classes from these modules are not used anywhere (it is clear, that classes from API modules are used). So, JPMS doesn't add these modules to layer. As I understand, if I spoke about implementation modules on boot layer, I could use --add-modules jvm argument. However, I couldn't find any information how to force JPMS load my module (even if its classes are not used) for dynamically created layers. Could anyone say how to do it? -- Best regards, Alex Orlov
