src/main/java/org/apache/log4j/rule/ExistsRule.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.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.Stack;
import org.apache.log4j.chainsaw.logevents.ChainsawLoggingEvent;
import org.apache.log4j.spi.LoggingEventFieldResolver;

/**
 * A Rule class implementing a not null (and not empty string) check.
 *
 * @author Scott Deboy (sdeboy@apache.org)
 */
public class ExistsRule extends AbstractRule {
    /**
     * Serialization id.
     */
    static final long serialVersionUID = -5386265224649967464L;
    /**
     * field resolver.
     */
    private static final LoggingEventFieldResolver RESOLVER = LoggingEventFieldResolver.getInstance();
    /**
     * field name.
     */
    private final String field;

    /**
     * Create new instance.
     * @param fld field name.
     */
    private ExistsRule(final String fld) {
        super();
        if (!RESOLVER.isField(fld)) {
            throw new IllegalArgumentException("Invalid EXISTS rule - " + fld + " is not a supported field");
        }

        this.field = fld;
    }

    /**
     * Get an instance of ExistsRule.
     * @param field field.
     * @return instance of ExistsRule.
     */
    public static Rule getRule(final String field) {
        return new ExistsRule(field);
    }

    /**
     * Create an instance of ExistsRule using the
     * top name on the stack.
     * @param stack stack
     * @return instance of ExistsRule.
     */
    public static Rule getRule(final Stack stack) {
        if (stack.size() < 1) {
            throw new IllegalArgumentException(
                    "Invalid EXISTS rule - expected one parameter but received " + stack.size());
        }

        return new ExistsRule(stack.pop().toString());
    }

    /**
     * {@inheritDoc}
     */
    public boolean evaluate(final ChainsawLoggingEvent event, Map matches) {
        Object p2 = RESOLVER.getValue(field, event);

        boolean result = !((p2 == null) || (p2.toString().isEmpty()));
        if (result && matches != null) {
            Set entries = (Set) matches.get(field.toUpperCase());
            if (entries == null) {
                entries = new HashSet();
                matches.put(field.toUpperCase(), entries);
            }
            entries.add(p2);
        }
        return result;
    }
}