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/*****************************************************************************
* Copyright (c) 2018 Christian W. Damus and others.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Christian W. Damus - Initial API and implementation
*
*****************************************************************************/
package org.eclipse.papyrus.uml.diagram.sequence.util;
import java.util.function.BooleanSupplier;
import org.eclipse.papyrus.uml.diagram.sequence.part.UMLDiagramEditorPlugin;
import org.eclipse.swt.widgets.Display;
/**
* A deferred action that posts itself asynchronously on the {@link Display} thread
* and re-tries some limited number of times if its initial conditions are not met.
*
* @since 5.0
*/
public abstract class RetryingDeferredAction {
private static final int DEFAULT_RETRY_LIMIT = 3;
private final Display display;
private final int retryLimit;
private volatile int retries;
/**
* Initializes me.
*
* @param display
* the display on which I post myself for delayed execution
* @param retryLimit
* the number of times I may retry
*
* @throws IllegalArgumentException
* if the retry limit is non-positive
*/
public RetryingDeferredAction(Display display, int retryLimit) {
super();
if (retryLimit <= 0) {
throw new IllegalArgumentException("retry limit must be positive"); //$NON-NLS-1$
}
this.display = display;
this.retryLimit = retryLimit;
}
/**
* Initializes me with the default number (three) of retries.
*
* @param display
* the display on which I post myself for delayed execution
*/
public RetryingDeferredAction(Display display) {
this(display, DEFAULT_RETRY_LIMIT);
}
/**
* Initializes me with the current display.
*
* @param retryLimit
* the number of times I may retry
*
* @throws IllegalArgumentException
* if the retry limit is non-positive
*/
public RetryingDeferredAction(int retryLimit) {
this(Display.getCurrent(), retryLimit);
}
/**
* Initializes me with the current display and the default number (three) of retries.
*/
public RetryingDeferredAction() {
this(Display.getCurrent(), DEFAULT_RETRY_LIMIT);
}
/**
* Try an {@code action} up to the given number of times, deferred on the {@code display} thread.
* This is useful for the simple case where it is only necessary to attempt to perform the
* action and there is no need for an explicit preparation step.
*
* @param display
* the display on which thread to defer the {@code action}
* @param retryLimit
* the maximal number of times to tr-try the {@code action}
* @param action
* the action to perform. If it returns {@code false}, then it will
* be re-tried (unless the limit is exceeded, of course)
*
* @throws IllegalArgumentException
* if the retry limit is non-positive
*/
public static void defer(Display display, int retryLimit, BooleanSupplier action) {
new Wrapper(display, retryLimit, action).post();
}
/**
* Try an {@code action} up to the default number (three) of times, deferred on the {@code display} thread.
*
* @param display
* the display on which thread to defer the {@code action}
* @param action
* the action to perform
*/
public static void defer(Display display, BooleanSupplier action) {
defer(display, DEFAULT_RETRY_LIMIT, action);
}
/**
* Try an {@code action} up to the given number of times, deferred on the current display thread.
*
* @param retryLimit
* the maximal number of times to tr-try the {@code action}
* @param action
* the action to perform
*
* @throws IllegalArgumentException
* if the retry limit is non-positive
*/
public static void defer(int retryLimit, BooleanSupplier action) {
defer(Display.getCurrent(), retryLimit, action);
}
/**
* Try an {@code action} up to the default number (three) of times, deferred on the current display thread.
*
* @param action
* the action to perform
*/
public static void defer(BooleanSupplier action) {
defer(Display.getCurrent(), DEFAULT_RETRY_LIMIT, action);
}
/**
* Prepares me for execution, testing my initial conditions and setting up any
* required state.
*
* @return {@code true} if my initial conditions are satisfied and I may {@link #perform()};
* {@code false}, otherwise
*/
protected abstract boolean prepare();
/**
* Performs me. Will not be called unless {@link #prepare()} returned {@code true}.
*/
protected abstract void perform();
private void run() {
if (prepare()) {
perform();
} else {
retries = retries + 1;
post();
}
}
/**
* Post me for deferred execution.
*/
public void post() {
if (retries < retryLimit) {
display.asyncExec(this::run);
} else {
UMLDiagramEditorPlugin.log.warn("Retry limit exceeded for " + this); //$NON-NLS-1$
}
}
//
// Nested types
//
private static final class Wrapper extends RetryingDeferredAction {
private final BooleanSupplier action;
Wrapper(Display display, int retryLimit, BooleanSupplier action) {
super(display, retryLimit);
this.action = action;
}
@Override
protected boolean prepare() {
return action.getAsBoolean();
}
@Override
protected void perform() {
// Already done in the preparation step
}
}
}
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