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// Copyright 2015 The Bazel Authors. All rights reserved.
//
// 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.google.devtools.build.lib.query2.engine;
import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadCompatible;
import java.io.IOException;
import javax.annotation.Nullable;
/** A callback that can receive a finish event when there are no more partial results */
@ThreadCompatible
public abstract class OutputFormatterCallback<T> implements Callback<T> {
private IOException ioException;
/**
* This method will be called before any partial result are available.
*
* <p>It should be used for opening resources or sending a header to the output.
*/
public void start() throws IOException {
}
/**
* Same as start but for closing resources or writing a footer.
*
* <p>Will be called even in the case of an error.
*/
public void close(boolean failFast) throws InterruptedException, IOException {
}
/**
* Note that {@link Callback} interface does not throw IOExceptions. What this implementation does
* instead is throw {@code InterruptedException} and store the {@code IOException} in the {@code
* ioException} field. Users of this class should check on InterruptedException the field to
* disambiguate between real interruptions or IO Exceptions.
*/
@Override
public final void process(Iterable<T> partialResult) throws QueryException, InterruptedException {
try {
processOutput(partialResult);
} catch (IOException e) {
ioException = e;
throw new InterruptedException("Interrupting due to a IOException in the OutputFormatter");
}
}
public abstract void processOutput(Iterable<T> partialResult)
throws IOException, InterruptedException;
@Nullable
public IOException getIoException() {
return ioException;
}
/**
* Use an {@code OutputFormatterCallback} with an already computed set of targets. Note that this
* does not work in stream mode, as the {@code targets} would already be computed.
*
* <p>The intended usage of this method is to use {@code StreamedFormatter} formaters in non
* streaming contexts.
*/
public static <T> void processAllTargets(OutputFormatterCallback<T> callback,
Iterable<T> targets) throws IOException, InterruptedException {
boolean failFast = true;
try {
callback.start();
callback.process(targets);
failFast = false;
} catch (InterruptedException e) {
IOException ioException = callback.getIoException();
if (ioException != null) {
throw ioException;
}
throw e;
} catch (QueryException e) {
throw new IllegalStateException("This should not happen, as we are not running any query,"
+ " only printing the results:" + e.getMessage(), e);
} finally {
callback.close(failFast);
}
}
}
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