/**
* Try to load a module from this module loader. Returns {@code null} if the module is not found.
* The returned module may not yet be resolved. The returned module may have a different name than
* the given identifier if the identifier is an alias for another module.
*
* @param identifier the module identifier
* @return the module
* @throws ModuleLoadException if an error occurs while loading the module
*/
protected final Module loadModuleLocal(ModuleIdentifier identifier) throws ModuleLoadException {
FutureModule futureModule = moduleMap.get(identifier);
if (futureModule != null) {
return futureModule.getModule();
}
FutureModule newFuture = new FutureModule(identifier);
futureModule = moduleMap.putIfAbsent(identifier, newFuture);
if (futureModule != null) {
return futureModule.getModule();
}
boolean ok = false;
try {
final ModuleLogger log = Module.log;
log.trace("Locally loading module %s from %s", identifier, this);
final long startTime = Metrics.getCurrentCPUTime();
final ModuleSpec moduleSpec = findModule(identifier);
loadTimeUpdater.addAndGet(this, Metrics.getCurrentCPUTime() - startTime);
if (moduleSpec == null) {
log.trace("Module %s not found from %s", identifier, this);
return null;
}
if (!moduleSpec.getModuleIdentifier().equals(identifier)) {
throw new ModuleLoadException("Module loader found a module with the wrong name");
}
final Module module;
if (moduleSpec instanceof AliasModuleSpec) {
final ModuleIdentifier aliasTarget = ((AliasModuleSpec) moduleSpec).getAliasTarget();
try {
newFuture.setModule(module = loadModuleLocal(aliasTarget));
} catch (RuntimeException e) {
log.trace(e, "Failed to load module %s (alias for %s)", identifier, aliasTarget);
throw e;
} catch (Error e) {
log.trace(e, "Failed to load module %s (alias for %s)", identifier, aliasTarget);
throw e;
}
} else {
module = defineModule((ConcreteModuleSpec) moduleSpec, newFuture);
}
log.trace("Loaded module %s from %s", identifier, this);
ok = true;
return module;
} finally {
if (!ok) {
newFuture.setModule(null);
moduleMap.remove(identifier, newFuture);
}
}
}
/**
* Find an already-loaded module, returning {@code null} if the module isn't currently loaded. May
* block while the loaded state of the module is in question (if the module is being concurrently
* loaded from another thread, for example).
*
* @param identifier the module identifier
* @return the module, or {@code null} if it wasn't found
*/
protected final Module findLoadedModuleLocal(ModuleIdentifier identifier) {
FutureModule futureModule = moduleMap.get(identifier);
if (futureModule != null) {
try {
return futureModule.getModule();
} catch (ModuleNotFoundException e) {
return null;
}
} else {
return null;
}
}
/**
* Load a module based on an identifier.
*
* @param identifier The module identifier
* @return The loaded Module
* @throws ModuleLoadException if the Module can not be loaded
*/
public Module loadModule(ModuleIdentifier identifier) throws ModuleLoadException {
final Set<ModuleIdentifier> visited = VISITED.get();
if (visited.contains(identifier))
throw new ModuleLoadException(
"Failed to load " + identifier + "; module cycle discovered: " + visited);
FutureModule futureModule = moduleMap.get(identifier);
if (futureModule == null) {
FutureModule newFuture = new FutureModule(identifier);
futureModule = moduleMap.putIfAbsent(identifier, newFuture);
if (futureModule == null) {
visited.add(identifier);
try {
final Module module = findModule(identifier);
if (module == null) throw new ModuleNotFoundException(identifier.toString());
return module;
} finally {
visited.remove(identifier);
}
}
}
return futureModule.getModule();
}
