ratpack.exec.Fulfiller Maven / Gradle / Ivy
/*
* Copyright 2014 the original author or authors.
*
* 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 ratpack.exec;
import ratpack.api.NonBlocking;
import java.util.concurrent.CompletableFuture;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
/**
* A fulfiller of an asynchronous promise.
*
* This type is used to integrate with asynchronous APIs, via the {@link ExecControl#promise(ratpack.func.Action)} method.
* The following example shows usage during request processing.
*
* import ratpack.handling.InjectionHandler;
* import ratpack.handling.Context;
* import ratpack.exec.Promise;
* import ratpack.exec.Fulfiller;
* import ratpack.func.Action;
*
* // Some 3rd party asynchronous API
* public interface SomeAsyncApi {
* interface AsyncCallback {
* void onSuccess(String result);
* void onError(IOException e);
* }
*
* void doSomeAsyncOperation(AsyncCallback callback);
* }
*
* public class AsyncApiUsingHandler extends InjectionHandler {
* void handle(final Context context, final SomeAsyncApi asyncApi) {
* Promise<String> promise = context.promise(new Action<Fulfiller<String>>() {
* public void execute(final Fulfiller<String> fulfiller) {
* asyncApi.doSomeAsyncOperation(new SomeAsyncApi.AsyncCallback() {
* public void onSuccess(String result) {
* fulfiller.success(result);
* }
* public void onError(IOException e) {
* fulfiller.error(e);
* }
* });
* }
* });
*
* promise.then(new Action<String>() {
* public void execute(String string) {
* context.render(string);
* }
* });
* }
* }
*
*
* The methods of this method may be executed asynchronously.
* That is, the promise subscription my be invoked in a separate thread.
*
* @param the type of value that was promised.
* @see ExecControl#promise(ratpack.func.Action)
* @see Promise
*/
public interface Fulfiller {
/**
* Fulfills the promise with an error result.
*
* @param throwable the error result
*/
@NonBlocking
void error(Throwable throwable);
/**
* Fulfills the promise with the given value.
*
* @param value the value to provide to the promise subscriber
*/
@NonBlocking
void success(T value);
/**
* Fulfills via the given result.
*
* @param result the result to use to fulfill.
*/
default void accept(Result result) {
if (result.isSuccess()) {
success(result.getValue());
} else {
error(result.getThrowable());
}
}
/**
* Fulfills via the given completable future.
*
* @param future the future to use to fulfill
*/
default void accept(CompletableFuture future) {
future.handle((value, failure) -> {
if (failure == null) {
success(value);
} else {
error(failure);
}
return null;
});
}
/**
* Fulfills via the given ListenableFuture.
*
* @param listenableFuture the future to use to fulfill
*/
default void accept(ListenableFuture listenableFuture) {
Futures.addCallback(listenableFuture, new FutureCallback() {
@Override
public void onSuccess(T result) {
success(result);
}
@Override
public void onFailure(Throwable t) {
error(t);
}
});
}
}