Maybe it is simple question but still can find how to do it. Let's suppose I use the following code to create layer
ModuleFinder finder = ModuleFinder.of(moduleCPath);
ModuleLayer parent = ModuleLayer.boot();
Configuration cf = parent.configuration().resolve(finder, ModuleFinder.of(), Set.of("module-c"));
ClassLoader scl = ClassLoader.getSystemClassLoader();
ModuleLayer myLayer = parent.defineModulesWithOneLoader(cf, scl);
As I understand for myLayer one classloader was created. How can I get reference to this classloader having reference to myLayer and without knowing what classes can be inside myLayer modules?
When a ModuleLayer is created each Module gets mapped to a ClassLoader.
ModuleLayerA layer is created from a graph of modules in a Configuration and a function that maps each module to a ClassLoader.
A ModuleLayer has no concept of a ClassLoader because there is no guarantee that every Module will have the same ClassLoader. Instead, the ClassLoader is associated with each individual Module, which you can get via Module.getClassLoader().
Since you are using ModuleLayer.defineModulesWithOneLoader(Configuration,ClassLoader)1, however, there is a guarantee that each Module will have the same ClassLoader. This means you can get the ClassLoader from any Module in the ModuleLayer and consider it as the "ClassLoader of the ModuleLayer".
ModuleLayer layer = parent.defineModulesWithOneLoader(...);
ClassLoader loader = layer.modules().iterator().next().getClassLoader();
Note that this won't work as intended if:
ModuleLayer is empty (has no Modules).
iterator().next() will throw a NoSuchElementException.ModuleLayer via defineModulesWithManyLoaders(Configuration,ClassLoader)1
Module will have its own ClassLoader.ModuleLayer via defineModules(Configuration,Function) and the Function doesn't return the same ClassLoader every time.
Module to ClassLoader. Also, each ClassLoader can potentially have different parents. This method provides the most flexibility when defining ModuleLayers.1. The methods defineModulesWithOneLoader and defineModulesWithManyLoaders are, in effect, convenience methods for defineModules for two pre-definable use cases; each Module has the same ClassLoader and each Module has their own ClassLoader, respectively.
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