/**
* Initialize Jena.
*
* <p>This function is cheap to call when already initialized so can be called to be sure. A
* commonly used idiom in jena is a static initializer in key classes.
*
* <p>By default, initialization happens by using {@code ServiceLoader.load} to find {@link
* JenaSubsystemLifecycle} objects. See {@link #setSubsystemRegistry} to intercept that choice.
*/
public static void init() {
// Any other thread attempting to initialize as well will
// first test the volatile outside the lock; if it's
// not INITIALIZED, the thread will attempt to grab the lock
// and hence wait, then see initialized as true.
// But we need to cope with recursive calls of JenaSystem.init() as well.
// The same thread will not stop at the lock.
// Set initialized to true before a recursive call is possible
// handles this. The recursive call will see initialized true and
// and returnn on the first test.
// Net effect:
// After a top level call of JenaSystem.init() returns, tjena has
// finishes initialization.
// Recursive calls do not have this property.
if (initialized) return;
synchronized (initLock) {
if (initialized) {
logLifecycle("JenaSystem.init - return");
return;
}
// Catches recursive calls, same thread.
initialized = true;
logLifecycle("JenaSystem.init - start");
if (get() == null) setSubsystemRegistry(new JenaSubsystemRegistryBasic());
get().load();
// Debug : what did we find?
if (JenaSystem.DEBUG_INIT) {
logLifecycle("Found:");
get()
.snapshot()
.forEach(
mod -> logLifecycle(" %-20s [%d]", mod.getClass().getSimpleName(), mod.level()));
}
get().add(new JenaInitLevel0());
if (JenaSystem.DEBUG_INIT) {
logLifecycle("Initialization sequence:");
JenaSystem.forEach(
module ->
logLifecycle(" %-20s [%d]", module.getClass().getSimpleName(), module.level()));
}
JenaSystem.forEach(
module -> {
logLifecycle("Init: %s", module.getClass().getSimpleName());
module.start();
});
logLifecycle("JenaSystem.init - finish");
}
}
