code: ///////////////////////////////////////////////////////////////////////////////////////////////
  // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
  // Copyright (C) 2001-2023 the original author or authors.
  //
  // This library is free software; you can redistribute it and/or
  // modify it under the terms of the GNU Lesser General Public
  // License as published by the Free Software Foundation; either
  // version 2.1 of the License, or (at your option) any later version.
  //
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ///////////////////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle;
  
  import java.io.File;
  import java.io.OutputStream;
  import java.io.OutputStreamWriter;
  import java.io.PrintWriter;
  import java.nio.charset.StandardCharsets;
  
  import com.puppycrawl.tools.checkstyle.api.AuditEvent;
  import com.puppycrawl.tools.checkstyle.api.AuditListener;
  
  /**
   * Generates <b>suppressions.xml</b> file, based on violations occurred.
   * See issue <a href="https://github.com/checkstyle/checkstyle/issues/102">#102</a>
   */
  public class XpathFileGeneratorAuditListener
          extends AbstractAutomaticBean
          implements AuditListener {
  
      /** The " quote character. */
      private static final String QUOTE_CHAR = "\"";
  
      /**
       * Helper writer that allows easy encoding and printing.
       */
      private final PrintWriter writer;
  
      /** Close output stream in auditFinished. */
      private final boolean closeStream;
  
      /** Determines if xml header is printed. */
      private boolean isXmlHeaderPrinted;
  
      /**
       * Creates a new {@code SuppressionFileGenerator} instance.
       * Sets the output to a defined stream.
       *
       * @param out the output stream
       * @param outputStreamOptions if {@code CLOSE} stream should be closed in auditFinished()
       */
      public XpathFileGeneratorAuditListener(OutputStream out,
                                             OutputStreamOptions outputStreamOptions) {
          writer = new PrintWriter(new OutputStreamWriter(out, StandardCharsets.UTF_8));
          closeStream = outputStreamOptions == OutputStreamOptions.CLOSE;
      }
  
      @Override
      public void auditStarted(AuditEvent event) {
          // No code by default
      }
  
      @Override
      public void auditFinished(AuditEvent event) {
          if (isXmlHeaderPrinted) {
              writer.println("</suppressions>");
          }
  
          writer.flush();
          if (closeStream) {
              writer.close();
          }
      }
  
      @Override
      public void fileStarted(AuditEvent event) {
          // No code by default
      }
  
      @Override
      public void fileFinished(AuditEvent event) {
          // No code by default
      }
  
      @Override
      public void addError(AuditEvent event) {
          final String xpathQuery = XpathFileGeneratorAstFilter.findCorrespondingXpathQuery(event);
          if (xpathQuery != null) {
              printXmlHeader();
  
              final File file = new File(event.getFileName());
  
              writer.println("<suppress-xpath");
              writer.print("       files=\"");
              writer.print(file.getName());
              writer.println(QUOTE_CHAR);
  
              if (event.getModuleId() == null) {
                  final String checkName =
                          PackageObjectFactory.getShortFromFullModuleNames(event.getSourceName());
                  writer.print("       checks=\"");
                  writer.print(checkName);
              }
              else {
                  writer.print("       id=\"");
                  writer.print(event.getModuleId());
              }
              writer.println(QUOTE_CHAR);
  
              writer.print("       query=\"");
              writer.print(xpathQuery);
  
              writer.println("\"/>");
          }
      }
  
      @Override
      public void addException(AuditEvent event, Throwable throwable) {
          throw new UnsupportedOperationException("Operation is not supported");
      }
  
      /**
       * Prints XML header if only it was not printed before.
       */
      private void printXmlHeader() {
          if (!isXmlHeaderPrinted) {
              writer.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
              writer.println("<!DOCTYPE suppressions PUBLIC");
              writer.println("    \"-//Checkstyle//DTD SuppressionXpathFilter Experimental "
                      + "Configuration 1.2//EN\"");
              writer.println("    \"https://checkstyle.org/dtds/"
                      + "suppressions_1_2_xpath_experimental.dtd\">");
              writer.println("<suppressions>");
              isXmlHeaderPrinted = true;
          }
      }
  
      @Override
      protected void finishLocalSetup() {
          // No code by default
      }
  }
  