src/main/java/org/apache/log4j/rule/LikeRule.java

/*
 * 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
 *
 *      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 org.apache.log4j.rule;

import java.io.IOException;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.Stack;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
import org.apache.log4j.chainsaw.logevents.ChainsawLoggingEvent;
import org.apache.log4j.spi.LoggingEventFieldResolver;

/**
 * A Rule class supporting java.util.regex regular expression syntax.
 *
 * @author Scott Deboy (sdeboy@apache.org)
 */
public class LikeRule extends AbstractRule {
    /**
     * Serialization ID.
     */
    static final long serialVersionUID = -3375458885595683156L;

    /**
     * Resolver.
     */
    private static final LoggingEventFieldResolver RESOLVER = LoggingEventFieldResolver.getInstance();
    /**
     * Pattern.
     */
    private transient Pattern pattern;
    /**
     * Regular expression matcher.
     */
    private transient Matcher matcher = null;
    /**
     * Field.
     */
    private transient String field;

    /**
     * Create new instance.
     * @param field field
     * @param pattern pattern
     */
    private LikeRule(final String field, final Pattern pattern) {
        super();
        if (!RESOLVER.isField(field)) {
            throw new IllegalArgumentException("Invalid LIKE rule - " + field + " is not a supported field");
        }

        this.field = field;
        this.pattern = pattern;
    }

    /**
     * Create new instance from top two elements of stack.
     * @param stack stack
     * @return new instance
     */
    public static Rule getRule(final Stack stack) {
        if (stack.size() < 2) {
            throw new IllegalArgumentException(
                    "Invalid LIKE rule - expected two parameters but received " + stack.size());
        }

        String p2 = stack.pop().toString();
        String p1 = stack.pop().toString();
        return getRule(p1, p2);
    }

    /**
     * Create new instance.
     * @param field field
     * @param pattern pattern
     * @return new instance
     */
    public static Rule getRule(final String field, final String pattern) {
        try {
            return new LikeRule(field, Pattern.compile(pattern, Pattern.CASE_INSENSITIVE));
        } catch (PatternSyntaxException e) {
            throw new IllegalArgumentException("Invalid LIKE rule - " + e.getMessage());
        }
    }

    /** {@inheritDoc} */
    public boolean evaluate(final ChainsawLoggingEvent event, Map matches) {
        // no need to figure out what part of the string matched, just set the entire string as a match
        Object input = RESOLVER.getValue(field, event);
        if ((input != null) && (pattern != null)) {
            if (matcher == null) {
                matcher = pattern.matcher(input.toString());
            } else {
                matcher.reset(input.toString());
            }
            boolean result = matcher.matches();
            if (result && matches != null) {
                Set entries = (Set) matches.get(field.toUpperCase());
                if (entries == null) {
                    entries = new HashSet();
                    matches.put(field.toUpperCase(), entries);
                }
                entries.add(input);
            }
            return result;
        }
        return false;
    }

    /**
     * Deserialize the state of the object.
     *
     * @param in object input stream
     *
     * @throws IOException if IOException during deserialization
     * @throws ClassNotFoundException if class not found.
     */
    private void readObject(final java.io.ObjectInputStream in) throws IOException, ClassNotFoundException {
        try {
            field = (String) in.readObject();
            String patternString = (String) in.readObject();
            pattern = Pattern.compile(patternString, Pattern.CASE_INSENSITIVE);
        } catch (PatternSyntaxException e) {
            throw new IOException("Invalid LIKE rule - " + e.getMessage());
        }
    }

    /**
     * Serialize the state of the object.
     *
     * @param out object output stream
     *
     * @throws IOException if IOException during serialization
     */
    private void writeObject(final java.io.ObjectOutputStream out) throws IOException {
        out.writeObject(field);
        out.writeObject(pattern.pattern());
    }
}