RegexUtils.java

package marubinotto.util;

import static marubinotto.util.CollectionUtils.set;

import java.util.Set;

import org.apache.commons.lang.UnhandledException;
import org.apache.oro.text.regex.MalformedPatternException;
import org.apache.oro.text.regex.MatchResult;
import org.apache.oro.text.regex.Pattern;
import org.apache.oro.text.regex.PatternCompiler;
import org.apache.oro.text.regex.PatternMatcher;
import org.apache.oro.text.regex.PatternMatcherInput;
import org.apache.oro.text.regex.Perl5Compiler;
import org.apache.oro.text.regex.Substitution;
import org.apache.oro.text.regex.Util;

public class RegexUtils {

  private static PatternCompiler compiler = new Perl5Compiler();

  public static Pattern compile(String pattern) {
    synchronized (RegexUtils.class) {
      try {
        return compiler.compile(pattern);
      }
      catch (MalformedPatternException e) {
        throw new UnhandledException(e);
      }
    }
  }

  /**
   * s/pattern/substitution/ge
   */
  public static String substitute(
    PatternMatcher matcher, 
    Pattern pattern, 
    MatchProcessor processor, 
    String input) {

    Assert.Arg.notNull(matcher, "matcher");
    Assert.Arg.notNull(pattern, "pattern");
    Assert.Arg.notNull(processor, "processor");
    Assert.Arg.notNull(input, "input");

    Substitution substitution = new MatchProcessorSubstitution(processor);
    return Util.substitute(matcher, pattern, substitution, input, Util.SUBSTITUTE_ALL);
  }

  public static interface MatchProcessor {
    public String process(MatchResult match);
  }

  static class MatchProcessorSubstitution implements Substitution {
    private MatchProcessor processor;

    public MatchProcessorSubstitution(MatchProcessor processor) {
      Assert.Arg.notNull(processor, "processor");
      this.processor = processor;
    }

    public void appendSubstitution(
      StringBuffer buffer, 
      MatchResult match, 
      int substitutionCount, 
      PatternMatcherInput originalInput,
      PatternMatcher matcher, 
      Pattern pattern) {

      buffer.append(this.processor.process(match));
    }
  }

  private static final Set<Character> METACHARS = 
    set('\\', '+', '-', '?', '*', '.', '[', ']', '(', ')', '{', '}', '^', '$', '|');

  public static String escapeRegex(String pattern) {
    if (pattern == null) {
      return pattern;
    }
    StringBuffer escaped = new StringBuffer();
    for (int i = 0; i < pattern.length(); i++) {
      char character = pattern.charAt(i);
      if (METACHARS.contains(character)) {
        escaped.append("\\");
      }
      escaped.append(character);
    }
    return escaped.toString();
  }
}