問題描述
Làm cách nào để thêm phần phụ Log4J2 vào thời gian chạy theo chương trình? (How to add Log4J2 appenders at runtime programmatically?)
Is it possible to add Log4J2 appenders programmatically using the specifications from the XML configuration?
I plan to define it all in the log4j2.xml and then pick appenders situationally like this (won't compile):
if (arg[0].equals("log") ) {
Logger.getLogger("loggerNameFromXMLConfig").addAppender("appenderNameFromXMLConfig");
} else {
//...
}
參考解法
方法 1:
There have been a number of requests to support better programmatic configuration for Log4j 2. Sorry it took so long. As of Log4j 2.4, API was added to log4j‑core to facilitate programmatic configuration.
The new ConfigurationBuilder API allows users to construct component definitions. With this API, there is no need to work directly with actual configuration objects (like LoggerConfig and FileAppender) which require a lot of knowledge on how Log4j works under the hood. Component definitions are added to the ConfigurationBuilder, and once all the definitions have been collected all the actual configuration objects (like Loggers and Appenders) are constructed. It feels a bit like the XML configuration syntax, except that you are writing Java code.
Note that the new ConfigurationBuilder API allows user code to create a new configuration or completely replace the existing configuration. If your use case is different, and you want to programmatically modify (rather than replace) an existing configuration after Log4j was started, then you will need to work with actual configuration objects. In that case, please see the Programmatically Modifying the Current Configuration after Initialization section of the manual.
方法 2:
Edit: for the newest versions of log4j2, see https://stackoverflow.com/a/33472893/1899566 instead.
I get the impression they don't want you doing this, but this works for me:
<pre class="lang‑java prettyprint‑override">if (arg[0].equals("log") ) {
org.apache.logging.log4j.Logger logger
= org.apache.logging.log4j.LogManager.getLogger("loggerNameFromXMLConfig");
org.apache.logging.log4j.core.Logger coreLogger
= (org.apache.logging.log4j.core.Logger)logger;
org.apache.logging.log4j.core.LoggerContext context
= (org.apache.logging.log4j.core.LoggerContext)coreLogger.getContext();
org.apache.logging.log4j.core.config.BaseConfiguration configuration
= (org.apache.logging.log4j.core.config.BaseConfiguration)context.getConfiguration();
coreLogger.addAppender(configuration.getAppender("appenderNameFromXMLConfig"));
} else {
//...
}
</code></pre>
方法 3:
As I noted above, I couldn't get https://logging.apache.org/log4j/2.x/manual/customconfig.html#AddingToCurrent to work, at least, not the way I expected it to (my appender would never get messages routed to it). I did finally stumble across a pattern that works for me ‑ allowing me to add an appender at runtime, and have that appender actually get log messages routed to it.
Edit I removed a bunch of confusing code from here that wasn't doing anything....
LoggerContext lc = (LoggerContext) LogManager.getContext(false);
FileAppender fa = FileAppender.newBuilder().withName("mylogger").withAppend(false).withFileName(new File(outputDirectory, "ConsoleOutput.txt").toString())
.withLayout(PatternLayout.newBuilder().withPattern("%‑5p %d [%t] %C{2} (%F:%L) ‑ %m%n").build())
.setConfiguration(lc.getConfiguration()).build();
fa.start();
lc.getConfiguration().addAppender(fa);
lc.getRootLogger().addAppender(lc.getConfiguration().getAppender(fa.getName()));
lc.updateLoggers();
A key point for me, was that calling addAppender and passing your appender directly doesn't work, but asking for your appender back by name seems to. Which doesn't make sense... but since working, and I'm tired of wasting time on something that should be so simple....
方法 4:
In Log4j2 structure
‑‑‑"Config"‑‑‑
Appenders
Appender(0)
Console
Appender(1)
File
LoggerConfigs
‑‑ LoggerConfig(0)
‑‑ LoggerConfig(1)
‑‑ LoggerConfig(2)
‑‑‑‑"LoggerConfig"‑‑‑‑
‑ AppenderRefs
‑‑ AppenderRef(0)
‑‑ Name Console
‑‑ Level : DEBUG
‑ Appenders
‑‑ Appender(0)
‑‑ Name Console
‑‑ Level : DEBUG
‑ Level ‑‑ ALL
loggerConfig.getAppenders() ‑‑> Will return the Appenders in "Config". For me this is a BUG
loggerConfig.getAppenderRefs() ‑‑> is working well !!
方法 5:
I don't know if it's useful: An Appender can be added to a Logger by calling the addLoggerAppender method of the current Configuration. reference:http://logging.apache.org/log4j/2.x/manual/architecture.html
(by Brian Johnson、Remko Popma、Robert Fleming、user2163960、Christian Klugesherz、Xiaoyuan)
參考文件