content: /*
   *  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
   *
   *      https://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.tools.ant.util.regexp;
  
  import org.apache.tools.ant.BuildException;
  import org.apache.tools.ant.MagicNames;
  import org.apache.tools.ant.Project;
  import org.apache.tools.ant.util.ClasspathUtils;
  
  /**
   * Simple Factory Class that produces an implementation of RegexpMatcher based on the system
   * property <code>ant.regexp.regexpimpl</code> and the classes available.
   *
   * <p>
   * In a more general framework this class would be abstract and have a static newInstance method.
   * </p>
   *
   */
  public class RegexpMatcherFactory {
  
      /***
       * Create a new regular expression instance.
       * @return the matcher
       * @throws BuildException on error
       */
      public RegexpMatcher newRegexpMatcher() throws BuildException {
          return newRegexpMatcher(null);
      }
  
      /***
       * Create a new regular expression instance.
       *
       * @param p Project whose ant.regexp.regexpimpl property will be used.
       * @return the matcher
       * @throws BuildException on error
       */
      public RegexpMatcher newRegexpMatcher(Project p) throws BuildException {
          String systemDefault;
          if (p == null) {
              systemDefault = System.getProperty(MagicNames.REGEXP_IMPL);
          } else {
              systemDefault = p.getProperty(MagicNames.REGEXP_IMPL);
          }
  
          if (systemDefault != null) {
              return createInstance(systemDefault);
              // TODO     should we silently catch possible exceptions and try to
              //         load a different implementation?
          }
  
          return new Jdk14RegexpMatcher();
      }
  
      /**
       * Create an instance of a matcher from a classname.
       *
       * @param className a <code>String</code> value
       * @return a <code>RegexpMatcher</code> value
       * @exception BuildException if an error occurs
       */
      protected RegexpMatcher createInstance(String className) throws BuildException {
          return ClasspathUtils.newInstance(className,
              RegexpMatcherFactory.class.getClassLoader(), RegexpMatcher.class);
      }
  
      /**
       * Test if a particular class is available to be used.
       *
       * @param className a <code>String</code> value
       * @exception BuildException if an error occurs
       */
      protected void testAvailability(String className) throws BuildException {
          try {
              Class.forName(className);
          } catch (Throwable t) {
              throw new BuildException(t);
          }
      }
  
      /**
       * Checks if a RegExp-Matcher is available.
       * @param project  The project to check for (may be <code>null</code>)
       * @return <code>true</code> if available otherwise <code>false</code>
       */
      public static boolean regexpMatcherPresent(Project project) {
          try {
              // The factory throws a BuildException if no usable matcher
              // cannot be instantiated. We don't need the matcher itself here.
              new RegexpMatcherFactory().newRegexpMatcher(project);
              return true;
          } catch (Throwable ex) {
              return false;
          }
      }
  }
  