io.druid.data.input.MapPopulator.java Source code

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Here is the source code for io.druid.data.input.MapPopulator.java

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/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  Metamarkets 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 io.druid.data.input;

import com.google.common.base.Charsets;
import com.google.common.io.ByteSource;
import com.google.common.io.LineProcessor;
import com.metamx.common.parsers.Parser;

import java.io.IOException;
import java.util.Map;

/**
 * Simple class that takes a `ByteSource` and uses a `Parser<K, V>` to populate a `Map<K, V>`
 * The `ByteSource` must be UTF-8 encoded
 *
 * If this is handy for other use cases pleaes move this class into a common module
 */
public class MapPopulator<K, V> {
    private final Parser<K, V> parser;

    public MapPopulator(Parser<K, V> parser) {
        this.parser = parser;
    }

    /**
     * Read through the `source` line by line and populate `map` with the data returned from the `parser`
     *
     * @param source The ByteSource to read lines from
     * @param map    The map to populate
     *
     * @return The number of entries parsed
     *
     * @throws IOException
     */
    public long populate(final ByteSource source, final Map<K, V> map) throws IOException {
        return source.asCharSource(Charsets.UTF_8).readLines(new LineProcessor<Long>() {
            private long count = 0l;

            @Override
            public boolean processLine(String line) throws IOException {
                map.putAll(parser.parse(line));
                ++count;
                return true;
            }

            @Override
            public Long getResult() {
                return count;
            }
        });
    }
}