BagitFileWriter.java

package gov.loc.repository.bagit.writer;

import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
import java.util.ResourceBundle;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import gov.loc.repository.bagit.domain.Version;

/**
 * Responsible for writing the bagit.txt to the filesystem
 */
public final class BagitFileWriter {
  private static final Logger logger = LoggerFactory.getLogger(BagitFileWriter.class);
  private static final ResourceBundle messages = ResourceBundle.getBundle("MessageBundle");
  
  private BagitFileWriter(){
    //intentionally left empty
  }
  
  /**
   * Write the bagit.txt file in required UTF-8 encoding.
   * 
   * @param version the version of the bag to write out
   * @param encoding the encoding of the tag files
   * @param outputDir the root of the bag
   * 
   * @throws IOException if there was a problem writing the file
   */
  public static void writeBagitFile(final Version version, final Charset encoding, final Path outputDir) throws IOException{
    final Path bagitPath = outputDir.resolve("bagit.txt");
    logger.debug(messages.getString("write_bagit_file_to_path"), outputDir);
    
    final String firstLine = "BagIt-Version: " + version + System.lineSeparator();
    logger.debug(messages.getString("writing_line_to_file"), firstLine, bagitPath);
    Files.write(bagitPath, firstLine.getBytes(StandardCharsets.UTF_8), 
        StandardOpenOption.WRITE, StandardOpenOption.TRUNCATE_EXISTING, StandardOpenOption.CREATE);
    
    final String secondLine = "Tag-File-Character-Encoding: " + encoding + System.lineSeparator();
    logger.debug(messages.getString("writing_line_to_file"), secondLine, bagitPath);
    Files.write(bagitPath, secondLine.getBytes(StandardCharsets.UTF_8), StandardOpenOption.WRITE, StandardOpenOption.APPEND);
  }
}