com.google.mr4c.sources.AggregateFileSource.java Source code

Introduction

Here is the source code for com.google.mr4c.sources.AggregateFileSource.java

Source

/**
  * Copyright 2014 Google Inc. 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.mr4c.sources;

import java.io.IOException;
import java.net.URI;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import org.apache.commons.collections.CollectionUtils;

/**
  * Aggregator of various file sources into a single read-only source of files
*/
public class AggregateFileSource implements FileSource {

    private List<FileSource> m_sources;

    public AggregateFileSource(List<FileSource> sources) {
        m_sources = sources;
    }

    public List<String> getAllFileNames() throws IOException {
        List<String> names = new ArrayList<String>();
        for (FileSource src : m_sources) {
            List<String> newNames = src.getAllFileNames();
            Collection<String> dups = CollectionUtils.intersection(names, newNames);
            if (!dups.isEmpty()) {
                throw new IllegalStateException("Found the following repeated file names: " + dups);
            }
            names.addAll(newNames);
        }
        return names;
    }

    public DataFileSource getFileSource(String fileName) throws IOException {
        DataFileSource src = getFileSourceOnlyIfExists(fileName);
        if (src == null) {
            throw new IllegalArgumentException(String.format("No file named [%s] found", fileName));
        }
        return src;
    }

    public boolean fileExists(String fileName) throws IOException {
        for (FileSource src : m_sources) {
            if (src.fileExists(fileName)) {
                return true;
            }
        }
        return false;
    }

    public DataFileSource getFileSourceOnlyIfExists(String fileName) throws IOException {
        for (FileSource src : m_sources) {
            if (src.fileExists(fileName)) {
                return src.getFileSource(fileName);
            }
        }
        return null;
    }

    public DataFileSink getFileSink(String fileName) throws IOException {
        throw new UnsupportedOperationException("File sinks not avaiable from aggregate file source");
    }

    public void close() throws IOException {
        for (FileSource src : m_sources) {
            src.close();
        }
    }

    public void ensureExists() throws IOException {
        for (FileSource src : m_sources) {
            src.ensureExists();
        }
    }

    public void clear() throws IOException {
        throw new UnsupportedOperationException("Clear not avaiable for aggregate file source");
    }

    public String getDescription() {
        return String.format("Aggregate of %d file sources", m_sources.size());
    }

}