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/*
* #%L
* *********************************************************************************************************************
*
* SteelBlue
* http://steelblue.tidalwave.it - hg clone https://bitbucket.org/tidalwave/steelblue-src
* %%
* Copyright (C) 2015 - 2015 Tidalwave s.a.s. (http://tidalwave.it)
* %%
*
* *********************************************************************************************************************
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*
* *********************************************************************************************************************
*
* $Id: JavaFXSafeProxyCreator.java,v b51d7da7bd2c 2015/04/16 20:50:00 fabrizio $
*
* *********************************************************************************************************************
* #L%
*/
package it.tidalwave.ui.javafx;
import javax.annotation.Nonnull;
import java.lang.reflect.Proxy;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.io.IOException;
import javafx.fxml.FXMLLoader;
import javafx.scene.Node;
import javafx.application.Platform;
import it.tidalwave.role.ui.javafx.impl.util.JavaFXSafeProxy;
import lombok.Getter;
import lombok.extern.slf4j.Slf4j;
/***********************************************************************************************************************
*
* This facility class create a thread-safe proxy for the JavaFX delegate (controller). Thread-safe means that it can
* be called by any thread and the JavaFX UI related stuff will be safely invoked in the JavaFX UI Thread.
* It is usually used in this way:
*
*
* @Configurable
* public class JavaFxFooBarPresentation implements FooBarPresentation
* {
* private static final String FXML_URL = "/my/package/javafx/FooBar.fxml";
*
* @Inject
* private Provider <Service>> service;
*
* private final NodeAndDelegate nad = createNodeAndDelegate(getClass(), FXML_URL);
*
* private final FooBarPresentation delegate = nad.getDelegate();
*
* public void showUp()
* {
* service.get().doSomething(nad.getNode());
* }
*
* public void showData (final String data)
* {
* delegate.showData(data);
* }
* }
*
*
* The method {@link #createNodeAndDelegate(java.lang.Class, java.lang.String)} safely invokes the {@link FXMLLoader}
* and returns a {@link NodeAndDelegate} that contains both the visual {@link Node} and its delegate (controller). The
* latter is wrapped by a safe proxy that makes sure that any method invpcation (such as {@code showData()} in the
* example is again executed in the JavaFX UI Thread.
*
* For method returning {@code void}, the method invocation is asynchronous; that is, the caller is not blocked waiting
* for the method execution completion. If a return value is provided, the invocation is synchronous, and the caller
* will correctly wait the completion of the execution in order to get the result value.
*
* A typical JavaFX delegate (controller) looks like:
*
*
*
* No only all the methods invoked on the delegate are guaranteed to run in the JavaFX UI thread, but also its
* constructor, as per JavaFX requirements.
*
* There are some caveat to take care of, though, to avoid triggering a deadlock, when the presentation is integrated
* with Spring and dependency injection, as in the example above. First, any injected service into the JavaFX delegate
* must be referenced by an indirect {@link Provider}. Second, any method that dereferences an injected object and
* that is called during the Spring initialization code (for instance, by another class {@link @PostConstruct} must
* not return any value.
*
* The reason for the deadlock is that during Spring bean initialization and creation (for instance
* {@code JavaFxFooBarPresentation}) the set of beans is locked. Then {@code createNodeAndDelegate()} requires the
* creation of {@code JavaFxFooBarPresentationDelegate} in the JavaFX UI thread. At this point, any direct
* [@code @Inject} (not by means of {@code Provider}) would require access to the set of Spring beans - and here we go
* with the deadlock.
*
* Only using {@code Provider}s avoids the problem since they defer the access to the Spring beans. In case of
* dependency resolution, being in a {@code void} method avoids the problem as the invocation is synchronous.
*
* Note that, Because the implementation doesn't use {@code synchronized} but other concurrent synchronization
* facilities, is likely that the deadlock is not detected by a debugger.
*
* @author Fabrizio Giudici
* @version $Id: JavaFXSafeProxyCreator.java,v b51d7da7bd2c 2015/04/16 20:50:00 fabrizio $
*
**********************************************************************************************************************/
@Slf4j
public class JavaFXSafeProxyCreator
{
/*******************************************************************************************************************
*
*
*
******************************************************************************************************************/
public static class NodeAndDelegate
{
@Getter @Nonnull
private final Node node;
@Nonnull
private final Object safeDelegate;
@Nonnull
public T getDelegate()
{
return (T)safeDelegate;
}
public NodeAndDelegate (final @Nonnull Class clazz, final @Nonnull String resource)
throws IOException
{
log.debug("NodeAndDelegate({}, {})", clazz, resource);
assert Platform.isFxApplicationThread() : "Not in JavaFX UI Thread";
final FXMLLoader loader = new FXMLLoader(clazz.getResource(resource));
node = (Node)loader.load();
final T jfxController = loader.getController();
final Class interfaceClass = (Class)jfxController.getClass().getInterfaces()[0]; // FIXME
safeDelegate = JavaFXSafeProxyCreator.createSafeProxy(jfxController, interfaceClass);
log.debug(">>>> load({}, {}) completed", clazz, resource);
}
}
/*******************************************************************************************************************
*
*
*
******************************************************************************************************************/
@Nonnull
public static NodeAndDelegate createNodeAndDelegate (final @Nonnull Class clazz,
final @Nonnull String resource)
{
log.debug("createNodeAndDelegate({}, {})", clazz, resource);
final CountDownLatch latch = new CountDownLatch(1);
final AtomicReference nad = new AtomicReference<>();
final AtomicReference exception = new AtomicReference<>();
Platform.runLater(() ->
{
try
{
nad.set(new NodeAndDelegate(clazz, resource));
}
catch (RuntimeException e)
{
exception.set(e);
}
catch (Exception e)
{
exception.set(new RuntimeException(e));
}
latch.countDown();
});
try
{
latch.await(10, TimeUnit.SECONDS); // FIXME
}
catch (InterruptedException e)
{
throw new RuntimeException(e);
}
if (exception.get() != null)
{
throw exception.get();
}
return nad.get();
}
/*******************************************************************************************************************
*
*
*
******************************************************************************************************************/
@Nonnull
public static T createSafeProxy (final @Nonnull T target, final Class interfaceClass)
{
return (T)Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(),
new Class[] { interfaceClass },
new JavaFXSafeProxy<>(target));
}
}
