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18 package org.apache.log4j.pattern;
19
20 import org.apache.log4j.spi.LoggingEvent;
21
22
23 /***
24 * LoggingEventPatternConverter is a base class for pattern converters
25 * that can format information from instances of LoggingEvent.
26 *
27 * @author Curt Arnold
28 *
29 */
30 public abstract class LoggingEventPatternConverter extends PatternConverter {
31 /***
32 * Constructs an instance of LoggingEventPatternConverter.
33 * @param name name of converter.
34 * @param style CSS style for output.
35 */
36 protected LoggingEventPatternConverter(
37 final String name, final String style) {
38 super(name, style);
39 }
40
41 /***
42 * Formats an event into a string buffer.
43 * @param event event to format, may not be null.
44 * @param toAppendTo string buffer to which the formatted event will be appended. May not be null.
45 */
46 public abstract void format(
47 final LoggingEvent event, final StringBuffer toAppendTo);
48
49 /***
50 * {@inheritDoc}
51 */
52 public void format(final Object obj, final StringBuffer output) {
53 if (obj instanceof LoggingEvent) {
54 format((LoggingEvent) obj, output);
55 }
56 }
57
58 /***
59 * Normally pattern converters are not meant to handle Exceptions although
60 * few pattern converters might.
61 *
62 * By examining the return values for this method, the containing layout will
63 * determine whether it handles throwables or not.
64
65 * @return true if this PatternConverter handles throwables
66 */
67 public boolean handlesThrowable() {
68 return false;
69 }
70 }