com.gwtplatform.dispatch.client.DelegatingDispatchRequest Maven / Gradle / Ivy
/**
* Copyright 2011 ArcBees Inc.
*
* 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.
*/
package com.gwtplatform.dispatch.client;
import com.gwtplatform.dispatch.shared.DispatchRequest;
/**
* An implementation of {@link DispatchRequest} that is used in conjunction with
* {@link com.gwtplatform.dispatch.client.actionhandler.ClientActionHandler ClientActionHandler}s.
*
* As the ClientActionHandler may be provided asynchronously, the
* {@link ClientActionHandlerDispatchRequest} will initially not contain an {@link DispatchRequest}.
* Once the {@link com.gwtplatform.dispatch.client.actionhandler.ClientActionHandler ClientActionHandler} is
* executed, this be populated with a {@link DelegatingDispatchRequest} by
* calling {@link #setDelegate(DispatchRequest)}.
*
* @author Brendan Doherty
*/
public class DelegatingDispatchRequest implements DispatchRequest {
private boolean cancelled;
private DispatchRequest delegate;
public DelegatingDispatchRequest() {
}
/**
* Populates the {@link DelegatingDispatchRequest} object with a
* {@link DispatchRequest}. If the code that requested the command to be
* executed has already chosen to cancel the {@link DispatchRequest}, the
* {@link DispatchRequest} that has been passed will be immediately cancelled.
*
* @param delegate The {@link DispatchRequest} object.
*/
public void setDelegate(DispatchRequest delegate) {
if (cancelled) {
if (delegate != null) {
this.delegate.cancel();
}
} else {
if (delegate == null) {
throw new NullPointerException("delegate");
}
if (this.delegate != null) {
throw new RuntimeException("Delegate can only be set once.");
}
this.delegate = delegate;
}
}
@Override
public void cancel() {
if (delegate != null) {
delegate.cancel();
} else {
cancelled = true;
}
}
@Override
public boolean isPending() {
if (delegate != null) {
return delegate.isPending();
} else {
return !cancelled;
}
}
}