-
-
Notifications
You must be signed in to change notification settings - Fork 973
/
manual.html
executable file
·624 lines (499 loc) · 25.6 KB
/
manual.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<title>SLF4J Manual</title>
<link rel="stylesheet" type="text/css" media="screen" href="css/site.css" />
<link rel="stylesheet" type="text/css" href="css/prettify.css" />
</head>
<body onload="prettyPrint(); decorate();">
<script type="text/javascript">prefix='';</script>
<script type="text/javascript" src="js/prettify.js"></script>
<script type="text/javascript" src="js/jquery-min.js"></script>
<script type="text/javascript" src="js/decorator.js"></script>
<script type="text/javascript" src="templates/header.js"></script>
<div id="left">
<script type="text/javascript" src="templates/left.js"></script>
</div>
<div id="right">
<script src="templates/right.js" type="text/javascript"></script>
</div>
<div id="content">
<h2>SLF4J user manual</h2>
<p>The Simple Logging Facade for Java (SLF4J) serves as a simple
facade or abstraction for various logging frameworks, such as
java.util.logging, logback and log4j. SLF4J allows the end-user to
plug in the desired logging framework at <em>deployment</em> time.
Note that SLF4J-enabling your library/application implies the
addition of only a single mandatory dependency, namely
<em>slf4j-api-${project.version}.jar</em>.</p>
<p><span class="label">since 1.6.0</span> If no binding is found on the
class path, then SLF4J will default to a no-operation
implementation.
</p>
<p><span class="label">since 1.7.0</span> Printing methods in the
<a href="apidocs/org/slf4j/Logger.html"><code>Logger</code></a>
interface now offer variants accepting <a
href="http://docs.oracle.com/javase/1.5.0/docs/guide/language/varargs.html">varargs</a>
instead of <code>Object[]</code>. This change implies that SLF4J
requires JDK 1.5 or later. Under the hood the Java compiler
transforms the varargs part in methods into
<code>Object[]</code>. Thus, the Logger interface generated by the
compiler is indistinguishable in 1.7.x from its 1.6.x
counterpart. It follows that SLF4J version 1.7.x is totally 100%
no-ifs-or-buts compatible with SLF4J version 1.6.x.
</p>
<p><span class="label">since 1.7.5</span> Significant improvement
in logger retrieval times. Given the extent of the improvement,
users are highly encouraged to migrate to SLF4J 1.7.5 or later.
</p>
<p><span class="label">since 1.7.9</span> By setting the
<code>slf4j.detectLoggerNameMismatch</code> system property to
true, SLF4J can automatically <a
href="codes.html#loggerNameMismatch">spot incorrectly named
loggers</a>.
</p>
<p><span class="label">since 2.0.0</span> SLF4J API version 2.0.0
requires Java 8 and introduces a backward-compatible fluent logging
API. By backward-compatible, we mean that existing logging
frameworks do not have to be changed in order for the user to
benefit from the <a href="#fluent">fluent logging API</a>.
</p>
<h3 class="doAnchor" name="hello_world">Hello World</h3>
<p>As customary in programming tradition, here is an example
illustrating the simplest way to output "Hello world" using SLF4J.
It begins by getting a logger with the name "HelloWorld". This
logger is in turn used to log the message "Hello World".
</p>
<pre class="prettyprint source">import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class HelloWorld {
public static void main(String[] args) {
Logger logger = LoggerFactory.getLogger(HelloWorld.class);
logger.info("Hello World");
}
}</pre>
<p>To run this example, you first need to <a
href="download.html">download the slf4j distribution</a>, and
then to unpack it. Once that is done, add the file
<em>slf4j-api-${latest.stable.version}.jar</em> to your class path.</p>
<p>Compiling and running <em>HelloWorld</em> will result in the
following output being printed on the console.</p>
<pre>SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.</pre>
<p>This warning is printed because no slf4j binding could be
found on your class path.</p>
<p>The warning will disappear as soon as you add a <a
href="#swapping">binding</a> to your class path. Assuming you add
<em>slf4j-simple-${latest.stable.version}.jar</em> so that your class
path contains:</p>
<ul>
<li>slf4j-api-${latest.stable.version}.jar</li>
<li>slf4j-simple-${latest.stable.version}.jar</li>
</ul>
<p>Compiling and running <em>HelloWorld</em> will now result in
the following output on the console.</p>
<pre class="output">0 [main] INFO HelloWorld - Hello World</pre>
<h3 class="doAnchor" name="typical_usage">Typical usage
pattern</h3>
<p>The sample code below illustrates the typical usage pattern
for SLF4J. Note the use of {}-placeholders on line 15. See the
question <a href="faq.html#logging_performance">"What is the
fastest way of logging?"</a> in the FAQ for more details.
</p>
<p></p>
<pre class="prettyprint source"> 1: <b>import org.slf4j.Logger;</b>
2: <b>import org.slf4j.LoggerFactory;</b>
3:
4: public class Wombat {
5:
6: <b>final Logger logger = LoggerFactory.getLogger(Wombat.class);</b>
7: Integer t;
8: Integer oldT;
9:
10: public void setTemperature(Integer temperature) {
11:
12: oldT = t;
13: t = temperature;
14:
15: <b>logger.debug("Temperature set to {}. Old temperature was {}.", t, oldT);</b>
16:
17: if(temperature.intValue() > 50) {
18: <b>logger.info("Temperature has risen above 50 degrees.");</b>
19: }
20: }
21: } </pre>
<h3 class="doAnchor" name="fluent">Fluent Logging API</h3>
<p>As of version 2.0, SLF4J API introduces a fluent API.</p>
<p>The idea is to build a logging event piece by piece with a <a
href="apidocs/org/slf4j/spi/LoggingEventBuilder.html">LoggingEventBuilder</a>
and to log once the event is fully built. The
<code>atTrace()</code>, <code>atDebug()</code>,
<code>atInfo()</code>, <code>atWarn()</code> and
<code>atError()</code> methods new in the
<code>org.slf4j.Logger</code> interface return an instance of <a
href="apidocs/org/slf4j/spi/LoggingEventBuilder.html"><code>LoggingEventBuilder</code></a>. For
disabled log levels, the returned
<code>LoggingEventBuilder</code> instance does nothing, thus
preserving the nano-second level performance of the regular
logging interface.</p>
<p>Here are few usage examples:</p>
<p>The statement</p>
<pre class="prettyprint source">logger.atInfo().log("Hello world");</pre>
<p>is equivalent to:</p>
<pre class="prettyprint source">logger.info("Hello world.");</pre>
<p>The following statements are all equivalent:</p>
<pre class="prettyprint source">
int newT = 15;
int oldT = 16;
// using classical API
logger.debug("Temperature set to {}. Old temperature was {}.", newT, oldT);
// using fluent API, add arguments one by one and then log message
logger.<b>atDebug()</b>.addArgument(newT).addArgument(oldT).log("Temperature set to {}. Old temperature was {}.");
// using fluent API, log message with arguments
logger.<b>atDebug()</b>.log("Temperature set to {}. Old temperature was {}.", newT, oldT);
// using fluent API, add one argument and then log message providing one more argument
logger.<b>atDebug()</b>.addArgument(newT).log("Temperature set to {}. Old temperature was {}.", oldT);
// using fluent API, add one argument with a Supplier and then log message with one more argument.
// Assume the method t16() returns 16.
logger.<b>atDebug()</b>.addArgument(() -> t16()).log(msg, "Temperature set to {}. Old temperature was {}.", oldT);
</pre>
<p>The fluent logging API allows the specification of many
different type of data to a <code>org.slf4j.Logger</code>
without a combinatorial explosion in the number of methods in
the <code>Logger</code> interface.</p>
<p>It is now possible to pass multiple <a
href="apidocs/org/slf4j/Marker.html">Markers</a>, pass arguments
with a <a
href="https://docs.oracle.com/javase/8/docs/api/java/util/function/Supplier.html">Supplier</a>
or pass multiple key-value pairs. Key-value pairs are
particularly useful in conjuction with log data analysers which
can interpret them automatically.</p>
<p>The following log statements are equivalent:</p>
<pre class="prettyprint source">
int newT = 15;
int oldT = 16;
// using classical API
logger.debug("oldT={} newT={} Temperature changed.", newT, oldT);
// using fluent API
logger.atDebug().<b>addKeyValue("oldT", oldT)</b>.addKeyValue("newT", newT).log("Temperature changed.");
</pre>
<h3 class="doAnchor" name="swapping">Binding with a logging
framework at deployment time</h3>
<p>As mentioned previously, SLF4J supports various logging
frameworks. The SLF4J distribution ships with several jar files
referred to as "SLF4J bindings", with each binding corresponding
to a supported framework. </p>
<dl>
<dt><em>slf4j-log4j12-${latest.stable.version}.jar</em>
</dt>
<dd>Binding for <a
href="http://logging.apache.org/log4j/1.2/index.html">log4j
version 1.2</a>, a widely used logging framework. You also
need to place <em>log4j.jar</em> on your class path.<p/></dd>
<dt><em>slf4j-jdk14-${latest.stable.version}.jar</em> </dt>
<dd>Binding for java.util.logging, also referred to as JDK 1.4
logging <p/></dd>
<dt><em>slf4j-nop-${latest.stable.version}.jar</em></dt>
<dd>Binding for <a
href="http://www.slf4j.org/api/org/slf4j/helpers/NOPLogger.html">NOP</a>,
silently discarding all logging.<p/></dd>
<dt><em>slf4j-simple-${latest.stable.version}.jar</em></dt>
<dd>Binding for <a
href="http://www.slf4j.org/apidocs/org/slf4j/impl/SimpleLogger.html">Simple
</a> implementation, which outputs all events to
System.err. Only messages of level INFO and higher are
printed. This binding may be useful in the context of small
applications.<p/></dd>
<dt><em>slf4j-jcl-${latest.stable.version}.jar</em></dt>
<dd>Binding for <a
href="http://commons.apache.org/logging/">Jakarta Commons
Logging</a>. This binding will delegate all SLF4J logging to
JCL.<p/>
</dd>
<dt><em>logback-classic-${logback.version}.jar (requires logback-core-${logback.version}.jar)</em></dt>
<dd><span class="label notice">Native implementation</span> There are also
SLF4J bindings external to the SLF4J project, e.g. <a
href="http://logback.qos.ch/">logback</a> which implements
SLF4J natively. Logback's
<a href="http://logback.qos.ch/apidocs/ch/qos/logback/classic/Logger.html">
<code>ch.qos.logback.classic.Logger</code></a> class is a
direct implementation of SLF4J's <a
href="http://www.slf4j.org/apidocs/org/slf4j/Logger.html">
<code>org.slf4j.Logger</code></a> interface. Thus, using SLF4J
in conjunction with logback involves strictly zero memory and
computational overhead.
</dd>
</dl>
<p>
</p>
<p>To switch logging frameworks, just replace slf4j bindings on
your class path. For example, to switch from java.util.logging
to log4j, just replace slf4j-jdk14-${latest.stable.version}.jar with
slf4j-log4j12-${latest.stable.version}.jar.
</p>
<p>SLF4J does not rely on any special class loader machinery. In
fact, each SLF4J binding is hardwired <em>at compile time</em>
to use one and only one specific logging framework. For
example, the slf4j-log4j12-${latest.stable.version}.jar binding is
bound at compile time to use log4j. In your code, in addition
to <em>slf4j-api-${latest.stable.version}.jar</em>, you simply drop
<b>one and only one</b> binding of your choice onto the
appropriate class path location. Do not place more than one
binding on your class path. Here is a graphical illustration of
the general idea.
</p>
<p><a href="images/concrete-bindings.png">
<img border="1" src="images/concrete-bindings.png" alt="click to enlarge" width="800"/>
</a></p>
<p>The SLF4J interfaces and their various adapters are extremely
simple. Most developers familiar with the Java language should
be able to read and fully understand the code in less than one
hour. No knowledge of class loaders is necessary as SLF4J does
not make use nor does it directly access any class loaders. As a
consequence, SLF4J suffers from none of the class loader
problems or memory leaks observed with Jakarta Commons Logging
(JCL).
</p>
<p>Given the simplicity of the SLF4J interfaces and its
deployment model, developers of new logging frameworks should
find it very easy to write SLF4J bindings.
</p>
<h3 class="doAnchor" name="libraries">Libraries</h3>
<p>Authors of widely-distributed components and libraries may
code against the SLF4J interface in order to avoid imposing an
logging framework on their end-user. Thus, the end-user may
choose the desired logging framework at deployment time by
inserting the corresponding slf4j binding on the classpath,
which may be changed later by replacing an existing binding with
another on the class path and restarting the application. This
approach has proven to be simple and very robust.
</p>
<p><b>As of SLF4J version 1.6.0</b>, if no binding is found on
the class path, then slf4j-api will default to a no-operation
implementation discarding all log requests. Thus, instead of
throwing a <code>NoClassDefFoundError</code> because the
<code>org.slf4j.impl.StaticLoggerBinder</code> class is missing,
SLF4J version 1.6.0 and later will emit a single warning message
about the absence of a binding and proceed to discard all log
requests without further protest. For example, let Wombat be
some biology-related framework depending on SLF4J for
logging. In order to avoid imposing a logging framework on the
end-user, Wombat's distribution includes <em>slf4j-api.jar</em>
but no binding. Even in the absence of any SLF4J binding on the
class path, Wombat's distribution will still work
out-of-the-box, and without requiring the end-user to download a
binding from SLF4J's web-site. Only when the end-user decides to
enable logging will she need to install the SLF4J binding
corresponding to the logging framework chosen by her.
</p>
<p><span class="label">Basic rule</span> <b>Embedded components
such as libraries or frameworks should not declare a dependency
on any SLF4J binding but only depend on slf4j-api</b>. When a
library declares a transitive dependency on a specific binding,
that binding is imposed on the end-user negating the purpose of
SLF4J. Note that declaring a non-transitive dependency on a
binding, for example for testing, does not affect the
end-user.</p>
<p>SLF4J usage in embedded components is also discussed in the
FAQ in relation with <a
href="faq.html#configure_logging">logging configuration</a>, <a
href="faq.html#optional_dependency">dependency reduction</a> and
<a href="faq.html#optional_dependency">testing</a>.</p>
<h3 class="doAnchor" name="projectDep">Declaring project
dependencies for logging</h3>
<p>Given Maven's transitive dependency rules, for "regular"
projects (not libraries or frameworks) declaring logging
dependencies can be accomplished with a single dependency
declaration.
</p>
<p><span class="label notice">logback-classic</span> If you wish
to use logback-classic as the underlying logging framework, all
you need to do is to declare "ch.qos.logback:logback-classic" as
a dependency in your <em>pom.xml</em> file as shown below. In
addition to <em>logback-classic-${logback.version}.jar</em>,
this will pull <em>slf4j-api-${latest.stable.version}.jar</em> as well
as <em>logback-core-${logback.version}.jar</em> into your
project. Note that explicitly declaring a dependency on
<em>logback-core-${logback.version}</em> or
<em>slf4j-api-${latest.stable.version}.jar</em> is not wrong and may
be necessary to impose the correct version of said artifacts by
virtue of Maven's "nearest definition" dependency mediation
rule.
</p>
<pre class="prettyprint source"><dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>${logback.version}</version>
</dependency></pre>
<p/>
<p><span class="label notice">log4j</span> If you wish to use
log4j as the underlying logging framework, all you need to do is
to declare "org.slf4j:slf4j-log4j12" as a dependency in your
<em>pom.xml</em> file as shown below. In addition to
<em>slf4j-log4j12-${latest.stable.version}.jar</em>, this will pull
<em>slf4j-api-${latest.stable.version}.jar</em> as well as
<em>log4j-${log4j.version}.jar</em> into your project. Note
that explicitly declaring a dependency on
<em>log4j-${log4j.version}.jar</em> or
<em>slf4j-api-${latest.stable.version}.jar</em> is not wrong and may
be necessary to impose the correct version of said artifacts by
virtue of Maven's "nearest definition" dependency mediation
rule.</p>
<pre class="prettyprint source"><dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>${latest.stable.version}</version>
</dependency></pre>
<p/>
<p><span class="label notice">java.util.logging</span> If you
wish to use java.util.logging as the underlying logging
framework, all you need to do is to declare
"org.slf4j:slf4j-jdk14" as a dependency in your <em>pom.xml</em>
file as shown below. In addition to
<em>slf4j-jdk14-${latest.stable.version}.jar</em>, this will pull
<em>slf4j-api-${latest.stable.version}.jar</em> into your project.
Note that explicitly declaring a dependency on
<em>slf4j-api-${latest.stable.version}.jar</em> is not wrong and may
be necessary to impose the correct version of said artifact by
virtue of Maven's "nearest definition" dependency mediation
rule.</p>
<pre class="prettyprint source"><dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-jdk14</artifactId>
<version>${latest.stable.version}</version>
</dependency></pre>
<h3 class="doAnchor" name="compatibility">Binary
compatibility</h3>
<p>An SLF4J binding designates an artifact such as
<em>slf4j-jdk14.jar</em> or <em>slf4j-log4j12.jar</em> used to
<em>bind</em> slf4j to an underlying logging framework, say,
java.util.logging and respectively log4j.
</p>
<p class="highlight">From the client's perspective all versions
of slf4j-api are compatible. Client code compiled with
slf4j-api-N.jar will run perfectly fine with slf4j-api-M.jar for
any N and M. You only need to ensure that the version of your
binding matches that of the slf4j-api.jar. You do not have to
worry about the version of slf4j-api.jar used by a given
dependency in your project. </p>
<p>Mixing different versions of <em>slf4j-api.jar</em> and SLF4J
binding can cause problems. For example, if you are using
slf4j-api-${latest.stable.version}.jar, then you should also use
slf4j-simple-${latest.stable.version}.jar, using
slf4j-simple-1.5.5.jar will not work.</p>
<p>However, from the client's perspective all versions of
slf4j-api are compatible. Client code compiled with
<em>slf4j-api-N.jar</em> will run perfectly fine with
<em>slf4j-api-M.jar</em> for any N and M. You only need to
ensure that the version of your binding matches that of the
slf4j-api.jar. You do not have to worry about the version of
slf4j-api.jar used by a given dependency in your project. You
can always use any version of <em>slf4j-api.jar</em>, and as
long as the version of <em>slf4j-api.jar</em> and its binding
match, you should be fine.
</p>
<p>At initialization time, if SLF4J suspects that there may be
an slf4j-api vs. binding version mismatch problem, it will emit
a warning about the suspected mismatch.
</p>
<h3 class="doAnchor" name="consolidate">Consolidate logging via
SLF4J</h3>
<p>Often times, a given project will depend on various
components which rely on logging APIs other than SLF4J. It is
common to find projects depending on a combination of JCL,
java.util.logging, log4j and SLF4J. It then becomes desirable to
consolidate logging through a single channel. SLF4J caters for
this common use-case by providing bridging modules for JCL,
java.util.logging and log4j. For more details, please refer to
the page on <a href="legacy.html"><b>Bridging legacy
APIs</b></a>.
</p>
<h3 class="doAnchor" name="mdc">Mapped Diagnostic Context (MDC) support</h3>
<p>"Mapped Diagnostic Context" is essentially a map maintained
by the logging framework where the application code provides
key-value pairs which can then be inserted by the logging
framework in log messages. MDC data can also be highly helpful
in filtering messages or triggering certain actions.</p>
<p>SLF4J supports MDC, or mapped diagnostic context. If the
underlying logging framework offers MDC functionality, then
SLF4J will delegate to the underlying framework's MDC. Note that
at this time, only log4j and logback offer MDC functionality. If
the underlying framework does not offer MDC, for example
java.util.logging, then SLF4J will still store MDC data but the
information therein will need to be retrieved by custom user
code.</p>
<p>Thus, as a SLF4J user, you can take advantage of MDC
information in the presence of log4j or logback, but without
forcing these logging frameworks upon your users as
dependencies.
</p>
<p>For more information on MDC please see the <a
href="http://logback.qos.ch/manual/mdc.html">chapter on MDC</a>
in the logback manual.
</p>
<h3 class="doAnchor" name="summary">Executive summary</h3>
<table class="bodyTable striped" cellspacing="4" cellpadding="4">
<tr>
<th align="left">Advantage</th>
<th align="left">Description</th>
</tr>
<tr>
<td>Select your logging framework at deployment time</td>
<td>The desired logging framework can be plugged in at
deployment time by inserting the appropriate jar file
(binding) on your class path.
</td>
</tr>
<tr>
<td>Fail-fast operation</td>
<td>Due to the way that classes are loaded by the JVM, the
framework binding will be verified automatically very early
on. If SLF4J cannot find a binding on the class path it
will emit a single warning message and default to
no-operation implementation.
</td>
</tr>
<tr>
<td>Bindings for popular logging frameworks
</td>
<td>SLF4J supports popular logging frameworks, namely log4j,
java.util.logging, Simple logging and NOP. The <a
href="http://logback.qos.ch">logback</a> project supports
SLF4J natively. </td>
</tr>
<tr>
<td>Bridging legacy logging APIs</td>
<td>
<p>The implementation of JCL over SLF4J, i.e
<em>jcl-over-slf4j.jar</em>, will allow your project to
migrate to SLF4J piecemeal, without breaking compatibility
with existing software using JCL. Similarly,
log4j-over-slf4j.jar and jul-to-slf4j modules will allow
you to redirect log4j and respectively java.util.logging
calls to SLF4J. See the page on <a
href="legacy.html">Bridging legacy APIs</a> for more
details.
</p>
</td>
</tr>
<tr>
<td>Migrate your source code</td>
<td>The <a href="migrator.html">slf4j-migrator</a> utility
can help you migrate your source to use SLF4J.
</td>
</tr>
<tr>
<td>Support for parameterized log messages</td>
<td>All SLF4J bindings support parameterized log messages
with significantly <a
href="faq.html#logging_performance">improved performance</a>
results.</td>
</tr>
</table>
<script src="templates/footer.js" type="text/javascript"></script>
</div>
</body>
</html>