1 /**
2 * Logback: the reliable, generic, fast and flexible logging framework.
3 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
4 *
5 * This program and the accompanying materials are dual-licensed under
6 * either the terms of the Eclipse Public License v1.0 as published by
7 * the Eclipse Foundation
8 *
9 * or (per the licensee's choosing)
10 *
11 * under the terms of the GNU Lesser General Public License version 2.1
12 * as published by the Free Software Foundation.
13 */
14 package ch.qos.logback.classic.pattern;
15
16 import ch.qos.logback.classic.LoggerContext;
17 import ch.qos.logback.classic.spi.ILoggingEvent;
18 import ch.qos.logback.core.Context;
19 import ch.qos.logback.core.pattern.CompositeConverter;
20 import ch.qos.logback.core.pattern.Converter;
21 import ch.qos.logback.core.pattern.ConverterUtil;
22 import ch.qos.logback.core.pattern.PostCompileProcessor;
23
24 public class EnsureExceptionHandling implements PostCompileProcessor<ILoggingEvent> {
25
26 /**
27 * This implementation checks if any of the converters in the chain handles
28 * exceptions. If not, then this method adds a
29 * {@link ExtendedThrowableProxyConverter} instance to the end of the chain.
30 * <p>
31 * This allows appenders using this layout to output exception information event
32 * if the user forgets to add %ex to the pattern. Note that the appenders
33 * defined in the Core package are not aware of exceptions nor LoggingEvents.
34 * <p>
35 * If for some reason the user wishes to NOT print exceptions, then she can add
36 * %nopex to the pattern.
37 *
38 *
39 */
40 public void process(Context context, Converter<ILoggingEvent> head) {
41 if (head == null) {
42 // this should never happen
43 throw new IllegalArgumentException("cannot process empty chain");
44 }
45 if (!chainHandlesThrowable(head)) {
46 Converter<ILoggingEvent> tail = ConverterUtil.findTail(head);
47 Converter<ILoggingEvent> exConverter = null;
48 LoggerContext loggerContext = (LoggerContext) context;
49 if (loggerContext.isPackagingDataEnabled()) {
50 exConverter = new ExtendedThrowableProxyConverter();
51 } else {
52 exConverter = new ThrowableProxyConverter();
53 }
54 tail.setNext(exConverter);
55 }
56 }
57
58 /**
59 * This method computes whether a chain of converters handles exceptions or not.
60 *
61 * @param head The first element of the chain
62 * @return true if it can handle throwables contained in logging events
63 */
64 public boolean chainHandlesThrowable(Converter<ILoggingEvent> head) {
65 Converter<ILoggingEvent> c = head;
66 while (c != null) {
67 if (c instanceof ThrowableHandlingConverter) {
68 return true;
69 } else if (c instanceof CompositeConverter) {
70 if (compositeHandlesThrowable((CompositeConverter<ILoggingEvent>) c)) {
71 return true;
72 }
73 }
74 c = c.getNext();
75 }
76 return false;
77 }
78
79 /**
80 * This method computes whether a composite converter handles exceptions or not.
81 *
82 * @param compositeConverter The composite converter
83 * @return true if it can handle throwables contained in logging events
84 */
85 public boolean compositeHandlesThrowable(CompositeConverter<ILoggingEvent> compositeConverter) {
86 Converter<ILoggingEvent> childConverter = compositeConverter.getChildConverter();
87
88 for (Converter<ILoggingEvent> c = childConverter; c != null; c = c.getNext()) {
89 if (c instanceof ThrowableHandlingConverter) {
90 return true;
91 } else if (c instanceof CompositeConverter) {
92 boolean r = compositeHandlesThrowable((CompositeConverter<ILoggingEvent>) c);
93 if (r)
94 return true;
95 }
96
97 }
98 return false;
99 }
100 }