| // 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 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); |
| } |
| } |
| } |