org.apache.ambari.server.serveraction.kerberos.AbstractKerberosDataFileReader.java Source code

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Here is the source code for org.apache.ambari.server.serveraction.kerberos.AbstractKerberosDataFileReader.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.ambari.server.serveraction.kerberos;

import org.apache.commons.csv.CSVFormat;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVRecord;

import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.Map;

/**
 * AbstractKerberosDataFileReader implements common code to read existing Kerberos data files.
 * <p/>
 * This class encapsulates a {@link org.apache.commons.csv.CSVParser} to read a CSV-formatted file.
 */
public abstract class AbstractKerberosDataFileReader implements Iterable<Map<String, String>> {

    private File file;
    private CSVParser csvParser = null;

    /**
     * Creates a new AbstractKerberosDataFileReader
     * <p/>
     * The file is opened upon creation, so there is no need to manually open it unless manually
     * closed before using.
     *
     * @param file a File declaring where to write the data
     * @throws java.io.IOException
     */
    protected AbstractKerberosDataFileReader(File file) throws IOException {
        this.file = file;
        open();
    }

    /**
     * Opens the data file for reading.
     * <p/>
     * This may be called multiple times and the appropriate action will occur depending on if the
     * file has been previously opened or closed.
     *
     * @throws java.io.IOException
     */
    public void open() throws IOException {
        if (isClosed()) {
            csvParser = CSVParser.parse(file, Charset.defaultCharset(), CSVFormat.DEFAULT.withHeader());
        }
    }

    /**
     * Tests this AbstractKerberosDataFileReader to see if the data file is closed.
     *
     * @return true if closed; otherwise false
     */
    public boolean isClosed() {
        return csvParser == null;
    }

    public void close() throws IOException {
        if (csvParser != null) {
            csvParser.close();
            csvParser = null;
        }
    }

    /**
     * Gets an iterator to use to access the records in the data file.
     * <p/>
     * Each item is a Map of column names to values.
     *
     * @return an Iterator of records from the data file, each record is represented as a Map of
     * column name (String) to column value (String)
     */
    @Override
    public Iterator<Map<String, String>> iterator() {
        return new Iterator<Map<String, String>>() {
            Iterator<CSVRecord> iterator = (csvParser == null) ? null : csvParser.iterator();

            @Override
            public boolean hasNext() {
                return (iterator != null) && iterator.hasNext();
            }

            @Override
            public Map<String, String> next() {
                return (iterator == null) ? null : iterator.next().toMap();
            }

            @Override
            public void remove() {
                if (iterator != null) {
                    iterator.remove();
                }
            }
        };
    }
}