001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.log4j.pattern;
019
020import org.apache.log4j.spi.LoggingEvent;
021import org.apache.log4j.spi.ThrowableInformation;
022
023
024/**
025 * Outputs the ThrowableInformation portion of the LoggingEvent.
026 * By default, outputs the full stack trace.  %throwable{none}
027 * or %throwable{0} suppresses the stack trace. %throwable{short}
028 * or %throwable{1} outputs just the first line.  %throwable{n}
029 * will output n lines for a positive integer or drop the last
030 * -n lines for a negative integer.
031 *
032 * @author Paul Smith
033 *
034 */
035public class ThrowableInformationPatternConverter
036  extends LoggingEventPatternConverter {
037
038  /**
039   * Maximum lines of stack trace to output.
040   */
041  private int maxLines = Integer.MAX_VALUE;
042
043  /**
044   * Private constructor.
045   * @param options options, may be null.
046   */
047  private ThrowableInformationPatternConverter(
048    final String[] options) {
049    super("Throwable", "throwable");
050
051    if ((options != null) && (options.length > 0)) {
052      if("none".equals(options[0])) {
053          maxLines = 0;
054      } else if("short".equals(options[0])) {
055          maxLines = 1;
056      } else {
057          try {
058              maxLines = Integer.parseInt(options[0]);
059          } catch(NumberFormatException ex) {
060          }
061      }
062    }
063  }
064
065  /**
066   * Gets an instance of the class.
067    * @param options pattern options, may be null.  If first element is "short",
068   * only the first line of the throwable will be formatted.
069   * @return instance of class.
070   */
071  public static ThrowableInformationPatternConverter newInstance(
072    final String[] options) {
073    return new ThrowableInformationPatternConverter(options);
074  }
075
076  /**
077   * {@inheritDoc}
078   */
079  public void format(final LoggingEvent event, final StringBuffer toAppendTo) {
080    if (maxLines != 0) {
081      ThrowableInformation information = event.getThrowableInformation();
082
083      if (information != null) {
084        String[] stringRep = information.getThrowableStrRep();
085
086        int length = stringRep.length;
087        if (maxLines < 0) {
088            length += maxLines;
089        } else if (length > maxLines) {
090            length = maxLines;
091        }
092
093        for (int i = 0; i < length; i++) {
094            String string = stringRep[i];
095            toAppendTo.append(string).append("\n");
096        }
097      }
098    }
099  }
100
101  /**
102   * This converter obviously handles throwables.
103   * @return true.
104   */
105  public boolean handlesThrowable() {
106    return true;
107  }
108}