You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.Dismiss alert
This provides observability into an application's runtime. (See {logging-services-url}/what-is-logging.html[What is logging?] page for a longer read.)
37
+
This provides observability into an application's runtime.
37
38
38
39
But we can do way better than a `printf()` statement!
39
40
40
41
* Enhance the message with additional information (timestamp, class & method name, line number, host, severity, etc.)
41
-
* Write the message in a different way, using a different **layout** (CSV, JSON, etc.)
42
+
* Write the message differently, using a different **layout** (CSV, JSON, etc.)
42
43
* Write the message to a different medium, using a different **appender** (file, socket, database, queue, etc.)
43
44
* Write only some of the messages, using a **filter** (e.g. filter by severity, content, etc.)
44
45
45
-
Log4j is versatile, industrial-grade Java logging framework delivering all these and more in one product.
46
+
Log4j is a versatile, industrial-grade Java logging framework delivering all these and more in one product.
46
47
It is essentially composed of a **logging API** and its **implementation**:
47
48
48
49
Log4j API::
49
50
The logging API your code (programmatically) logs through.
50
51
This needs to be available at compile-time and no configuration is needed.
51
52
52
53
Log4j Core::
53
-
The logging implementation which is responsible for filtering, routing, encoding, and appending log events.
54
+
The logging implementation is responsible for filtering, routing, encoding, and appending log events.
54
55
This needs to be available at runtime and configured by the user.
55
56
56
57
[#logging]
57
-
== How do I log using Log4j?
58
+
== How do I write logs using Log4j?
58
59
59
60
Add the `log4j-api` dependency to your application:
60
61
@@ -170,7 +171,7 @@ Let's try to walk through the most common ones.
170
171
==== Pass exception as the last extra argument
171
172
172
173
* [ ] Don't call `Throwable#printStackTrace()`!
173
-
This not only circumvents the logging, but can also leak sensitive information!
174
+
This not only circumvents the logging but can also leak sensitive information!
174
175
+
175
176
[source,java]
176
177
----
@@ -187,7 +188,7 @@ This prevents the log event from getting enriched with the exception.
187
188
----
188
189
189
190
* [ ] Don't provide both `Throwable#getMessage()` and `Throwable` itself!
190
-
This bloats the log message with duplicate exception message.
191
+
This bloats the log message with a duplicate exception message.
191
192
+
192
193
[source,java]
193
194
----
@@ -210,7 +211,7 @@ If you are using `String` concatenation while logging, you are doing something v
210
211
* [ ] Don't use `String` concatenation to format arguments!
211
212
This circumvents the handling of arguments by message type and layout.
212
213
More importantly, **this approach is prone to attacks!**
213
-
Imagine `userId` being provided by user with the following content:
214
+
Imagine `userId` being provided by the user with the following content:
214
215
`placeholders for non-existing args to trigger failure: {} {} \{dangerousLookup}`
215
216
+
216
217
[source,java]
@@ -330,11 +331,11 @@ Save the following XML document to `src/**main**/resources/log4j2.xml`:
330
331
331
332
</Configuration>
332
333
----
333
-
<1> xref:manual/appenders.adoc[Appenders] are responsible for writing log events to console, file, socket, database, etc.
334
+
<1> xref:manual/appenders.adoc[Appenders] are responsible for writing log events to the console, file, socket, database, etc.
334
335
<2> xref:manual/appenders.adoc#ConsoleAppender[Console Appender] is used to write logs to the console.
335
336
<3> xref:manual/json-template-layout.adoc[JSON Template Layout] is used to encode log events in JSON.
336
-
<4> Log events generated by classes in the `com.mycompany` package (incl. its subpackages) and that are of level `INFO` and higher (i.e., `WARN`, `ERROR`, `FATAL`) will be consumed.
337
-
<5> Unless specified otherwise, log events of level `WARN` and and higher will be consumed.
337
+
<4> Log events generated by classes in the `com.mycompany` package (incl. its sub packages) and that are of level `INFO` and higher (i.e., `WARN`, `ERROR`, `FATAL`) will be consumed.
338
+
<5> Unless specified otherwise, log events of level `WARN` and higher will be consumed.
338
339
<6> Unless specified otherwise, log events will be forwarded to the `console` appender defined earlier.
339
340
340
341
You are strongly advised to use a different Log4j configuration for tests.
@@ -471,5 +472,5 @@ See the xref:manual/architecture.adoc[] page.
471
472
472
473
Support::
473
474
Confused?
474
-
Having problem while setting up Log4j?
475
+
Having a problem while setting up Log4j?
475
476
See the {logging-services-url}/support.html[Support] page.
0 commit comments