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/*
 * 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.pattern;

import org.apache.log4j.spi.LoggingEvent;

import java.util.Iterator;
import java.util.Set;
import org.apache.log4j.helpers.*;

/**
 * Able to handle the contents of the LoggingEvent's Property bundle and either
 * output the entire contents of the properties in a similar format to the
 * java.util.Hashtable.toString(), or to output the value of a specific key
 * within the property bundle when this pattern converter has the option set.
 *
 * @author Paul Smith
 * @author Ceki Gülcü
 */
public final class PropertiesPatternConverter extends LoggingEventPatternConverter {
    /**
     * Name of property to output.
     */
    private final String option;

    /**
     * Private constructor.
     * 
     * @param options options, may be null.
     */
    private PropertiesPatternConverter(final String[] options) {
	super(((options != null) && (options.length > 0)) ? ("Property{" + options[0] + "}") : "Properties",
		"property");

	if ((options != null) && (options.length > 0)) {
	    option = options[0];
	} else {
	    option = null;
	}
    }

    /**
     * Obtains an instance of PropertiesPatternConverter.
     * 
     * @param options options, may be null or first element contains name of
     *                property to format.
     * @return instance of PropertiesPatternConverter.
     */
    public static PropertiesPatternConverter newInstance(final String[] options) {
	return new PropertiesPatternConverter(options);
    }

    /**
     * {@inheritDoc}
     */
    public void format(final LoggingEvent event, final StringBuffer toAppendTo) {
	// if there is no additional options, we output every single
	// Key/Value pair for the MDC in a similar format to Hashtable.toString()
	if (option == null) {
	    toAppendTo.append("{");

	    try {
		Set keySet = MDCKeySetExtractor.INSTANCE.getPropertyKeySet(event);
		if (keySet != null) {
		    for (Iterator i = keySet.iterator(); i.hasNext();) {
			Object item = i.next();
			Object val = event.getMDC(item.toString());
			toAppendTo.append("{").append(item).append(",").append(val).append("}");
		    }
		}
	    } catch (Exception ex) {
		LogLog.error("Unexpected exception while extracting MDC keys", ex);
	    }

	    toAppendTo.append("}");
	} else {
	    // otherwise they just want a single key output
	    Object val = event.getMDC(option);

	    if (val != null) {
		toAppendTo.append(val);
	    }
	}
    }
}