ComputeJobContinuationAdapter.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.ignite.compute;

import org.apache.ignite.resources.JobContextResource;
import org.jetbrains.annotations.Nullable;

/**
 * Convenience adapter for {@link ComputeJob} implementations. It provides the
 * following functionality:
 * <ul>
 * <li>
 *      Default implementation of {@link ComputeJob#cancel()} method and ability
 *      to check whether cancellation occurred.
 * </li>
 * <li>
 *      Ability to set and get a job arguments via {@link #setArguments(Object...)}
 *      and {@link #argument(int)} methods.
 * </li>
 * </ul>
 * Here is an example of how {@code ComputeJobAdapter} can be used from task logic
 * to create jobs. The example creates job adapter as anonymous class, but you
 * are free to create a separate class for it.
 * <pre name="code" class="java">
 * public class TestGridTask extends ComputeTaskSplitAdapter<String, Integer> {
 *     // Used to imitate some logic for the
 *     // sake of this example
 *     private int multiplier = 3;
 *
 *     @Override
 *     protected Collection<? extends ComputeJob> split(int gridSize, final String arg) throws IgniteCheckedException {
 *         List<ComputeJobAdapter<String>> jobs = new ArrayList<ComputeJobAdapter<String>>(gridSize);
 *
 *         for (int i = 0; i < gridSize; i++) {
 *             jobs.add(new ComputeJobAdapter() {
 *                 // Job execution logic.
 *                 public Object execute() throws IgniteCheckedException {
 *                     return multiplier * arg.length();
 *                 }
 *             });
 *        }
 *
 *         return jobs;
 *     }
 *
 *     // Aggregate multiple job results into
 *     // one task result.
 *     public Integer reduce(List<ComputeJobResult> results) throws IgniteCheckedException {
 *         int sum = 0;
 *
 *         // For the sake of this example, let's sum all results.
 *         for (ComputeJobResult res : results) {
 *             sum += (Integer)res.getData();
 *         }
 *
 *         return sum;
 *     }
 * }
 * </pre>
 */
public abstract class ComputeJobContinuationAdapter extends ComputeJobAdapter implements
    ComputeJobContinuation {
    /** */
    private static final long serialVersionUID = 0L;

    /** Job context. */
    @JobContextResource
    private transient ComputeJobContext jobCtx;

    /**
     * No-arg constructor.
     */
    protected ComputeJobContinuationAdapter() {
        /* No-op. */
    }

    /**
     * Creates job with one arguments. This constructor exists for better
     * backward compatibility with internal Ignite 2.x code.
     *
     * @param arg Job argument.
     */
    protected ComputeJobContinuationAdapter(@Nullable Object arg) {
        super(arg);
    }

    /**
     * Creates job with specified arguments.
     *
     * @param args Optional job arguments.
     */
    protected ComputeJobContinuationAdapter(@Nullable Object... args) {
        super(args);
    }

    /** {@inheritDoc} */
    @Override public boolean heldcc() {
        return jobCtx != null && jobCtx.heldcc();
    }

    /** {@inheritDoc} */
    @Override public void callcc() {
        if (jobCtx != null)
            jobCtx.callcc();
    }

    /** {@inheritDoc} */
    @Nullable @Override public <T> T holdcc() {
        return jobCtx == null ? null : jobCtx.<T>holdcc();
    }

    /** {@inheritDoc} */
    @Nullable @Override public <T> T holdcc(long timeout) {
        return jobCtx == null ? null : jobCtx.<T>holdcc(timeout);
    }
}