PatternMatcher.java

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// Copyright 2014 Cloudera Inc.
//
// Licensed 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 com.cloudera.impala.util;

import java.util.Arrays;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import com.google.common.collect.Lists;

public class PatternMatcher {
  // Patterns to match against. A string is considered to match if it matches
  // any of the patterns.
  private List<Pattern> patterns_;

  // Returns true if the candidate matches.
  public boolean matches(String candidate) {
    if (patterns_ == null) return true;
    if (patterns_.isEmpty()) return false;
    for (Pattern pattern: patterns_) {
      if (pattern.matcher(candidate).matches()) return true;
    }
    return false;
  }

  public static PatternMatcher createHivePatternMatcher(String hivePattern) {
    PatternMatcher result = new PatternMatcher();
    if (hivePattern != null) {
      result.patterns_ = Lists.newArrayList();
      // Hive ignores pretty much all metacharacters, so we have to escape them.
      final String metaCharacters = "+?.^()]\\/{}";
      final Pattern regex = Pattern.compile("([" + Pattern.quote(metaCharacters) + "])");

      for (String pattern: Arrays.asList(hivePattern.split("\\|"))) {
        Matcher matcher = regex.matcher(pattern);
        pattern = matcher.replaceAll("\\\\$1").replace("*", ".*");
        result.patterns_.add(Pattern.compile(pattern));
      }
    }
    return result;
  }

  public static PatternMatcher createJdbcPatternMatcher(String pattern) {
    String wildcardPattern = ".*";
    String workPattern = pattern;
    if (workPattern == null || pattern.isEmpty()) {
      workPattern = "%";
    }
    String result = workPattern
        .replaceAll("([^\\\\])%", "$1" + wildcardPattern)
        .replaceAll("\\\\%", "%")
        .replaceAll("^%", wildcardPattern)
        .replaceAll("([^\\\\])_", "$1.")
        .replaceAll("\\\\_", "_")
        .replaceAll("^_", ".");
    PatternMatcher matcher = new PatternMatcher();
    matcher.patterns_ = Lists.newArrayList();
    matcher.patterns_.add(Pattern.compile(result));
    return matcher;
  }
}