org.robotninjas.util.examples.ChainingExample.java Source code

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Here is the source code for org.robotninjas.util.examples.ChainingExample.java

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/**
 *    Copyright 2013 David Rusek <dave.rusek@gmail.com>
 *
 * 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 org.robotninjas.util.examples;

import com.google.common.collect.Lists;
import com.google.common.util.concurrent.AsyncFunction;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;

import java.io.File;
import java.net.URL;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.Executor;

import static com.google.common.util.concurrent.Futures.immediateFuture;

public class ChainingExample {

    private final Executor mainPool;
    private final Executor ioPool;

    public ChainingExample(Executor mainPool, Executor ioPool) {
        this.mainPool = mainPool;
        this.ioPool = ioPool;
    }

    public ListenableFuture<File> getMergedFileForUser(String user) throws Exception {
        ListenableFuture<List<String>> files = getFilesForUser("dave");
        ListenableFuture<List<URL>> urls = Futures.transform(files, locateFiles(), mainPool);
        ListenableFuture<List<File>> downloadedFiles = Futures.transform(urls, downloadFiles(), mainPool);
        return Futures.transform(downloadedFiles, mergeFiles(), ioPool);
    }

    ListenableFuture<List<String>> getFilesForUser(String user) {
        return immediateFuture((List<String>) Collections.EMPTY_LIST);
    }

    AsyncFunction<List<String>, List<URL>> locateFiles() {
        return new AsyncFunction<List<String>, List<URL>>() {
            @Override
            public ListenableFuture<List<URL>> apply(List<String> input) throws Exception {
                return immediateFuture((List<URL>) Lists.<URL>newArrayList());
            }
        };
    }

    AsyncFunction<List<URL>, List<File>> downloadFiles() {
        return new AsyncFunction<List<URL>, List<File>>() {
            @Override
            public ListenableFuture<List<File>> apply(List<URL> input) throws Exception {
                return immediateFuture((List<File>) Collections.EMPTY_LIST);
            }
        };
    }

    AsyncFunction<List<File>, File> mergeFiles() {
        return new AsyncFunction<List<File>, File>() {
            @Override
            public ListenableFuture<File> apply(List<File> input) throws Exception {
                return immediateFuture(new File(""));
            }
        };
    }

}