/*
* Copyright 2004-2023 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.engine;
import java.util.WeakHashMap;
import org.h2.message.Trace;
/**
* This class is responsible to close a database on JVM shutdown.
*/
class OnExitDatabaseCloser extends Thread {
private static final WeakHashMap<Database, Void> DATABASES = new WeakHashMap<>();
private static final Thread INSTANCE = new OnExitDatabaseCloser();
private static boolean registered;
private static boolean terminated;
/**
* Register database instance to close one on the JVM process shutdown.
*
* @param db Database instance.
*/
static synchronized void register(Database db) {
if (terminated) {
// Shutdown in progress
return;
}
DATABASES.put(db, null);
if (!registered) {
// Mark as registered unconditionally to avoid further attempts to register a
// shutdown hook in case of exception.
registered = true;
try {
Runtime.getRuntime().addShutdownHook(INSTANCE);
} catch (IllegalStateException e) {
// shutdown in progress - just don't register the handler
// (maybe an application wants to write something into a
// database at shutdown time)
} catch (SecurityException e) {
// applets may not do that - ignore
// Google App Engine doesn't allow
// to instantiate classes that extend Thread
}
}
}
/**
* Unregister database instance.
*
* @param db Database instance.
*/
static synchronized void unregister(Database db) {
if (terminated) {
// Shutdown in progress, do nothing
// This method can be called from the onShutdown()
return;
}
DATABASES.remove(db);
if (DATABASES.isEmpty() && registered) {
try {
Runtime.getRuntime().removeShutdownHook(INSTANCE);
} catch (IllegalStateException e) {
// ignore
} catch (SecurityException e) {
// applets may not do that - ignore
}
registered = false;
}
}
private static void onShutdown() {
synchronized(OnExitDatabaseCloser.class) {
terminated = true;
}
RuntimeException root = null;
for (Database database : DATABASES.keySet()) {
try {
database.close(true);
} catch (RuntimeException e) {
// this can happen when stopping a web application,
// if loading classes is no longer allowed
// it would throw an IllegalStateException
try {
database.getTrace(Trace.DATABASE).error(e, "could not close the database");
// if this was successful, we ignore the exception
// otherwise not
} catch (Throwable e2) {
e.addSuppressed(e2);
if (root == null) {
root = e;
} else {
root.addSuppressed(e);
}
}
}
}
if (root != null) {
throw root;
}
}
private OnExitDatabaseCloser() {
}
@Override
public void run() {
onShutdown();
}
}