A utility class that makes it easy to build objects from rows in a CSV file

CSVObjectReader.java

/*
 * Copyright 2017 tauTerra, LLC.
 *
 * 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.tauterra.utility;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.function.BiConsumer;
import java.util.function.Supplier;
import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVRecord;

/**
 * A utility class that makes it easy to build objects from rows in a CSV file.
 * <p>Depends: 'org.apache.commons', name: 'commons-csv', version: '1.5'</p>
 * <p>Usage:</p>
 * <pre>
 * CSVObjectReader&lt;MyObject&gt; myReader = new CSVObjectReader&lt;&gt;(() -> new MyObject());
 * myReader.addHandler("colNameA", (MyObject myObj, String value) -> myObj.setFoo(value));
 * myReader.addHandler("colNameB", (MyObject myObj, String value) -> myObj.setBar(value));
 * List&lt;MyObject&gt; rowsAsObjects = myReader.read(<em>csvInputStream</em>);
 * </pre>
 * 
 * @author Nicholas Folse
 */
public class CSVObjectReader<U> {

    final Supplier<U> objSupplier;
    final Map<String, BiConsumer<U, String>> colByNameHandlers = new HashMap<>();
    final List<BiConsumer<U, String>> colByIndexHandlers = new ArrayList<>();

    public CSVObjectReader(Supplier<U> objSupplier) {
        this.objSupplier = objSupplier;
    }

    public void addHandler(String columnName, BiConsumer<U, String> handler) {
        colByNameHandlers.put(columnName, handler);
    }
    
    public void addHandler(int columnIndex, BiConsumer<U, String> handler) {
        if (columnIndex > 32000) {
            return;
        }
        while (colByIndexHandlers.size() <= columnIndex) {
            colByIndexHandlers.add(null);
        }
        colByIndexHandlers.set(columnIndex, handler);
    }

    List<U> read(InputStream is) throws IOException {

        List<U> recordList = new ArrayList<>();

        try (InputStreamReader reader = new InputStreamReader(is)) {
            Iterable<CSVRecord> records = CSVFormat.RFC4180.withFirstRecordAsHeader().parse(reader);
            for (CSVRecord record : records) {
                U result = objSupplier.get();
                for (Entry<String, BiConsumer<U, String>> kv : colByNameHandlers.entrySet()) {
                    if (record.isMapped(kv.getKey()) && kv.getValue() != null) {
                        try {
                            kv.getValue().accept(result, record.get(kv.getKey()));
                        } catch (IllegalArgumentException e) {
                        }
                    }
                }
                int idx = 0;
                for (BiConsumer<U, String> setter : colByIndexHandlers) {
                    if (setter != null) {
                        String colValue = record.get(idx++);
                        if (colValue != null) {
                            setter.accept(result, colValue);
                        }
                    }
                }
                recordList.add(result);
            }
        }
        return recordList;
    }

}