--- /dev/null
+/*
+ * Jalview - A Sequence Alignment Editor and Viewer ($$Version-Rel$$)
+ * Copyright (C) $$Year-Rel$$ The Jalview Authors
+ *
+ * This file is part of Jalview.
+ *
+ * Jalview is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3
+ * of the License, or (at your option) any later version.
+ *
+ * Jalview is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ * PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Jalview. If not, see <http://www.gnu.org/licenses/>.
+ * The Jalview Authors are detailed in the 'AUTHORS' file.
+ */
+package jalview.bin;
+
+import jalview.util.Platform;
+
+import java.lang.reflect.Constructor;
+import java.lang.reflect.InvocationTargetException;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A class to hold singleton objects, whose scope (context) is
+ * <ul>
+ * <li>the Java runtime (JVM) when running as Java</li>
+ * <li>one 'applet', when running as JalviewJS</li>
+ * </ul>
+ * This allows separation of multiple JS applets running on the same browser
+ * page, each with their own 'singleton' instances.
+ * <p>
+ * Instance objects are held in a separate Map (keyed by Class) for each
+ * context. For Java, this is just a single static Map. For SwingJS, the map is
+ * stored as a field {@code _swingjsSingletons} of
+ * {@code Thread.currentThread.getThreadGroup()}, as a proxy for the applet.
+ * <p>
+ * Note that when an applet is stopped, its ThreadGroup is removed, allowing any
+ * singleton references to be garbage collected.
+ *
+ * @author hansonr
+ */
+public class ApplicationSingletonProvider
+{
+ /**
+ * A tagging interface to mark classes whose singleton instances may be served
+ * by {@code ApplicationSingletonProvider}, giving a distinct instance per JS
+ * 'applet'.
+ * <p>
+ * A class whose singleton should have global scope (be shared across all
+ * applets on a page) should <em>not</em> use this mechanism, but just provide
+ * a single instance (class static member) in the normal way.
+ */
+ public interface ApplicationSingletonI
+ {
+ }
+
+ /*
+ * Map used to hold singletons in JVM context
+ */
+ private static Map<Class<? extends ApplicationSingletonI>, ApplicationSingletonI> singletons = new HashMap<>();
+
+ /**
+ * private constructor for non-instantiable class
+ */
+ private ApplicationSingletonProvider()
+ {
+ }
+
+ /**
+ * Returns the singletons map for the current context (JVM for Java,
+ * ThreadGroup for JS), creating the map on the first request for each JS
+ * ThreadGroup
+ *
+ * @return
+ */
+ private static Map<Class<? extends ApplicationSingletonI>, ApplicationSingletonI> getContextMap()
+ {
+ @SuppressWarnings("unused")
+ ThreadGroup g = (Platform.isJS()
+ ? Thread.currentThread().getThreadGroup()
+ : null);
+ Map<Class<? extends ApplicationSingletonI>, ApplicationSingletonI> map = singletons;
+ /** @j2sNative map = g._swingjsSingletons; */
+ if (map == null)
+ {
+ map = new HashMap<>();
+ /** @j2sNative g._swingjsSingletons = map; */
+ }
+
+ return map;
+ }
+
+ /**
+ * Answers the singleton instance of the given class for the current context
+ * (JVM or SwingJS 'applet'). If no instance yet exists, one is created, by
+ * calling the class's no-argument constructor. Answers null if any error
+ * occurs (or occurred previously for the same class).
+ *
+ * @param c
+ * @return
+ */
+ public static ApplicationSingletonI getInstance(Class<? extends ApplicationSingletonI> c)
+ {
+ Map<Class<? extends ApplicationSingletonI>, ApplicationSingletonI> map = getContextMap();
+ if (map.containsKey(c))
+ {
+ /*
+ * singleton already created _or_ creation failed (null value stored)
+ */
+ return map.get(c);
+ }
+
+ /*
+ * create and save the singleton
+ */
+ ApplicationSingletonI o = map.get(c);
+ try
+ {
+ Constructor<? extends ApplicationSingletonI> con = c
+ .getDeclaredConstructor();
+ con.setAccessible(true);
+ o = con.newInstance();
+ } catch (IllegalAccessException | InstantiationException
+ | IllegalArgumentException | InvocationTargetException
+ | NoSuchMethodException | SecurityException e)
+ {
+ Cache.log.error("Failed to create singleton for " + c.toString()
+ + ", error was: " + e.toString());
+ e.printStackTrace();
+ }
+
+ /*
+ * store the new singleton; note that a
+ * null value is saved if construction failed
+ */
+ getContextMap().put(c, o);
+ return o;
+ }
+
+ /**
+ * Removes the current singleton instance of the given class from the current
+ * application context. This has the effect of ensuring that a new instance is
+ * created the next time one is requested.
+ *
+ * @param c
+ */
+ public static void removeInstance(
+ Class<? extends ApplicationSingletonI> c)
+ {
+ Map<Class<? extends ApplicationSingletonI>, ApplicationSingletonI> map = getContextMap();
+ if (map != null)
+ {
+ map.remove(c);
+ }
+ }
+}
git://source.jalview.org / jalview.git / blobdiff