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

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

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

/**
 * AbstractKerberosDataFileBuilder provides a generic facility to write a data file using some
 * underlying record-based file writer.
 * <p/>
 * This class encapsulates a {@link org.apache.commons.csv.CSVPrinter} to create a CSV-formatted file.
 */
public abstract class AbstractKerberosDataFileBuilder {

    private File file;
    private CSVPrinter csvPrinter;

    /**
     * Creates a new KerberosConfigDataFileBuilder
     * <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
     */
    public AbstractKerberosDataFileBuilder(File file) throws IOException {
        this.file = file;
        open();
    }

    /**
     * Opens the data file for writing.
     * <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()) {
            if (file == null) {
                throw new IOException("Missing file path");
            } else {
                csvPrinter = new CSVPrinter(new FileWriter(file, true), CSVFormat.DEFAULT);

                // If the file is empty, write the header; else don't write the header.
                if (file.length() == 0) {
                    // Write the header....
                    Iterable<?> headerRecord = getHeaderRecord();
                    csvPrinter.printRecord(headerRecord);
                }
            }
        }
    }

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

    /**
     * Closes the data file
     *
     * @throws java.io.IOException
     */
    public void close() throws IOException {
        if (csvPrinter != null) {
            csvPrinter.close();
            csvPrinter = null;
        }
    }

    /**
     * Appends a new record to the data file
     *
     * @param record a collection of Strings declaring values for the columns of the file
     * @throws java.io.IOException
     */
    protected void appendRecord(String... record) throws IOException {

        if (csvPrinter == null) {
            throw new IOException("Data file is not open");
        }

        csvPrinter.printRecord(record);
    }

    /**
     * Gets the header record for the CSV file
     *
     * @return an Iterable containing the (ordered) list of Strings declaring the columns names
     */
    protected abstract Iterable<String> getHeaderRecord();

}