org.jtrim2.taskgraph.basic.RestrictableNode Maven / Gradle / Ivy
package org.jtrim2.taskgraph.basic;
import java.util.Objects;
import org.jtrim2.taskgraph.TaskNodeKey;
/**
* Defines a node which a {@code TaskExecutionRestrictionStrategy} can restrict from being
* executed. Once, the {@code TaskExecutionRestrictionStrategy} decides that the associated
* node can be executed it should execute the {@link #release() release action} of this
* node.
*
* The release action should not be called multiple times. Releasing a task node does
* not imply that task will scheduled right away. Releasing only means, that the
* {@code TaskExecutionRestrictionStrategy} no longer wants to stop it from being executed.
*
*
Thread safety
* Methods of this class are allowed to be used from multiple threads concurrently.
*
* Synchronization transparency
* The {@link #release() release} method of this class is not required to be
* synchronization transparent but other methods are synchronization transparent.
*
* @see RestrictableTaskGraphExecutor
* @see TaskExecutionRestrictionStrategyFactory
*/
public final class RestrictableNode {
private final TaskNodeKey nodeKey;
private final Runnable releaseAction;
/**
* Creates a new {@code RestrictableNode} with the given key and action used to release
* this node.
*
* @param nodeKey the {@code TaskNodeKey} identifying the node which is to be restricted.
* This argument cannot be {@code null}.
* @param releaseAction the action to be executed to allow the associated node to be
* scheduled for execution. This argument cannot be {@code null}. It is highly recommended
* for the task action to be idempotent.
*/
public RestrictableNode(TaskNodeKey nodeKey, Runnable releaseAction) {
Objects.requireNonNull(nodeKey, "nodeKey");
Objects.requireNonNull(releaseAction, "releaseAction");
this.nodeKey = nodeKey;
this.releaseAction = releaseAction;
}
/**
* Returns the {@code TaskNodeKey} identifying the node which is to be restricted.
*
* @return the {@code TaskNodeKey} identifying the node which is to be restricted. This
* method never returns {@code null}.
*/
public TaskNodeKey getNodeKey() {
return nodeKey;
}
/**
* Returns the action to be called once the {@link TaskExecutionRestrictionStrategy}
* decides that the task can be scheduled for execution.
*
* The release action should not be called multiple times, regardless if it is done
* directly or by calling the {@link #release() release} method.
*
* @return the action to be called once the {@link TaskExecutionRestrictionStrategy}
* decides that the task can be scheduled for execution. This method never returns
* {@code null}.
*/
public Runnable getReleaseAction() {
return releaseAction;
}
/**
* Allows the associated task node to be scheduled for execution.
* This method is simply a convenience for:
*
* getReleaseAction().run();
*
*
* The release action should not be called multiple times, regardless if it is done
* directly or by calling the {@link #release() release} method.
*/
public void release() {
releaseAction.run();
}
/**
* Returns the string representation of this {@code RestrictableNode} in no particular
* format.
*
* This method is intended to be used for debugging only.
*
* @return the string representation of this object in no particular format.
* This method never returns {@code null}.
*/
@Override
public String toString() {
return "RestrictableNode{" + nodeKey + '}';
}
}