org.apache.druid.data.input.MapPopulator.java Source code

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

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/*
 * 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.druid.data.input;

import com.google.common.io.ByteSource;
import com.google.common.io.LineProcessor;
import org.apache.druid.java.util.common.ISE;
import org.apache.druid.java.util.common.parsers.Parser;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
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
 * <p>
 * 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;
    }

    public static class PopulateResult {
        private final int lines;
        private final int entries;

        public PopulateResult(int lines, int entries) {
            this.lines = lines;
            this.entries = entries;
        }

        public int getLines() {
            return lines;
        }

        public int getEntries() {
            return entries;
        }
    }

    /**
     * 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 number of lines read and entries parsed
     *
     * @throws IOException
     */
    public PopulateResult populate(final ByteSource source, final Map<K, V> map) throws IOException {
        return source.asCharSource(StandardCharsets.UTF_8).readLines(new LineProcessor<PopulateResult>() {
            private int lines = 0;
            private int entries = 0;

            @Override
            public boolean processLine(String line) {
                if (lines == Integer.MAX_VALUE) {
                    throw new ISE("Cannot read more than %,d lines", Integer.MAX_VALUE);
                }
                final Map<K, V> kvMap = parser.parseToMap(line);
                map.putAll(kvMap);
                lines++;
                entries += kvMap.size();
                return true;
            }

            @Override
            public PopulateResult getResult() {
                return new PopulateResult(lines, entries);
            }
        });
    }
}