My Java application which uses Log4j2 as its logging implementation has dependency on a 3rd party library which uses Log4j.
I am trying to set root logger appender and log level programatically in my application (using code below) for these 3rd party loggers, but these 3rd party library's loggers are still not logging to myAppender:
LoggerContext ctx = (LoggerContext) LogManager.getContext(false);
LoggerConfig loggerConfig = ctx.getConfiguration().getLoggerConfig(
LogManager.ROOT_LOGGER_NAME);
loggerConfig.addAppender(myAppender, Level.ERROR, null);
ctx.updateLoggers();
A solution I thought of was to use Log4jToSLF4JAdaptor to route log4j's logging to SLF4J and then use Log4JSLF4JImpl to route SLF4J's logging to my Log4J2 implementation but as stated here (https://logging.apache.org/log4j/2.0/log4j-slf4j-impl/index.html), it would lead to endless routing.
Can you please suggest how can I route logging of these 3rd party library's loggers to myAppender ?
For 3rd party libraries using the Log4j 1.x API: In addition to the log4j-api and log4j-core jar files, you need to add the log4j-1.2-api jar file to your classpath.
For 3rd party libraries using the SLF4J API: add log4j-api, log4j-core and the log4j-slf4j-impl jar files to your classpath (you also need the slf4j API jar).
For 3rd party libraries using JUL (java.util.logging): add log4j-api, log4j-core and the log4j-jul jar files to your classpath, as well as set the system property java.util.logging.manager to org.apache.logging.log4j.jul.LogManager.
Got my answer here: Configuring log4j2 and log4j using a single log4j2 xml file
Basically, we need to use log4j-1.2-api-2.0.jar to route all calls that our application makes to log4-1.2 API to log4j2 implementation.
Related
We wanted to switch from standard logback to log4j in Spring Boot 2.4.x.
For most modules, it is a no-brainer by simply removing the dependency of logback, but there are some modules, which are using pact-jvm as a shadow-jar dependency to be able to create the pact files from unit tests.
Now the odyssey begins, because pact needs logback and with the pact-jar on the classpath Spring recognizes the logback class it is looking for and decides to use logback instead of log4j as the logger in the tests.
Is there a possibility to create something like a log bean or a hidden configuration, which allows forcing Spring to use log4j instead of logback, also if logback is on the classpath?
Pact should not be an issue at this point, because the server is started as a standalone server from gradle. We only require the dependency to be able to start everything and to have the classes available.
Thanks!
You may follow these steps to configure log4j with spring boot
Add the log4j dependency to your module
Create logger object in your respective class and use the logger object to log the messages.
org.apache.log4j.Logger logger = org.apache.log4j.Logger.getLogger(<YourClassName>.class);
In your spring boot module/project add log4j.properties file in resources so that this will be available on class path at runtime. Following is sample content for the log4j.properties
log4j.rootLogger=INFO, stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n
Make sure that the spring boot module bundles the log4j jar when you build.
Once spring boot finds the log4j jar and the log4j.properties on the class path it will be able to initialize the log4j logger for you.
Yes, that's clear. The issue is, that Spring Boots Autoconfiguration is loading the logger for slf4j (sorry forgot that). So here it iterates over the supported candidates in the order:
logback
log4j
apache-log-commons
And it seems that it does not look for beans, it simply looks for the classes by reflection.
If we now start the app for testing together with pact server, Spring Boot resolves an Append* class and thinks, that this has to be the logger of our choice.
It creates the logback instance, which is searching for its config, but then it fails, because the config is for log4j.
I have a Spring Boot project with a dependency to a third party library. This library uses SLF4J with Log4j2 for logging, and has a log4j2.xml with a pattern layout defined.
The problem is that the pattern layout of this dependency is used as the pattern for my application, ignoring the layout defined in application.properties.
If I can't modify the source code of this third party lib, is possible to configure my app in order to ignore the log4j2.xml?
One solution that you can try is to define your own log4j2 configuration file and give its path in log4j.configurationFile system property. When you define your own log4j2 configuration file, you can control how much logging you want and in which pattern.
The reason behind this is - When Log4j starts it tries to locate all the ConfigurationFactory plugins and arrange them in weighted order from highest to lowest. And as per log4j2 Automation Configuration, setting system property log4j.configurationFile has highest weight.
If log4j will found configuration file using this system property, then it will not scan classpath for locating log4j2.xml file which is present in your dependent library.
I have a Tomcat server running a Spring-based servlet.
I've set up [project root]/src/log4j.properties file as below:
# Root logger option
log4j.rootLogger=WARN, stdout
# Redirect log messages to console
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%-5p %d{HH:mm:ss} %m [%c{3}:%L]%n
log4j.logger.com.martincarney.bugTracker=DEBUG
log4j.logger.com.martincarney.bugTracker.controller=ERROR
This correctly logs my own code just fine, but doesn't seem to have any effect on logging from within the various libraries I'm using. For example, I still get INFO logs from org.apache.* to the Eclipse console error stream during Tomcat startup, even if I add log4j.logger.org.apache=WARN to my log4j.properties.
I'm using slf4j-api and slf4j-log4j jars, obtained through Maven.
How can I take control of logging levels and targets outside my own code?
Some libraries use other logging frameworks like java.util.logging.
You could redirect logging with SLF4J, see SLF4J - Bridging legacy APIs:
Redirection for Jakarta Commons Logging:
To ease migration to SLF4J from JCL, SLF4J distributions include the jar file jcl-over-slf4j.jar. This jar file is intended as a drop-in replacement for JCL version 1.1.1. It implements the public API of JCL but using SLF4J underneath, hence the name "JCL over SLF4J."
Redirection for java.util.Logging (SLF4J API):
Installation via logging.properties configuration file:
// register SLF4JBridgeHandler as handler for the j.u.l. root logger
handlers = org.slf4j.bridge.SLF4JBridgeHandler
For configuration of java.util.Logging see JUL API.
Some libraries like Apache CXF supports more than one logging framework, see Apache CXF - Debugging and Logging .
log4j has a system property called log4j.debug, that when set by adding -Dlog4j.debug=true to your command line, prints out the information about how log4j configures itself (for example, the location of the con file it found and loaded).
I am looking for a similar capability for slf4j. Can we tell slf4j to print out how it is set and configured?
slf4j is wrapper for other loggin systems (the f in the name stands for facade), it does not have its own configuration.
With slf4j you can even use log4j as real logging library. If you are using logback as logging library along with slf4j there is an attribute debug for the main configuration tag (if you are using an xml file for configuring logback).
<configuration debug="true">
....your conf here
</configuration>
the logback mnanual can be found here
we have a standalone java project using log4j for logging,and we don't config log4j via the classpath configuration. we config it in my code as bellow:
String configLocation = System.getProperty("S_HOME") + File.separator + "config" + File.separator + "xxxLog.properties";
PropertyConfigurator.configure(configLocation)
but if we move to slf4j,how can I config log4j via slf4j?
THKS
You can't use slf4j for that, you just keep your old configuration code for log4j.
slf4j does not handle the configuration part, which would be very difficult to generalize for all supported logging systems. slf4j is just an API for handling logging calls that dispatches to a particular logging implementation. It also offers a number of bridges, such as redirecting java.util.logging to slf4j.
What happens with the log output is not part of the slf4j API.