Download Log4j2 Properties File
Helaine Timonere
We can use below log4j2.properties file logging output into the console. Please note that if no configuration file can be located then DefaultConfiguration will be used, and that also logs on to the console.
If we are using an external log4j2 configuration file, then we can provide the path of the configuration file using the application startup parameter or system property log4j2.configurationFile. Note that this property value is not restricted to a location on the local file system and may contain a URL.
A commonly seen approach is to set the log4j2.configurationFile property in the method annotated with @BeforeAll in the junit test class. This will allow an arbitrarily named file to be used during the test.
All available formats are functionally equivalent. For example, a configuration file in XML can be rewritten using the properties format (and the opposite) without any loss of functionality. However, the hierarchical nature of a Log4j configuration can be captured better in formats which naturally support nesting so XML, JSON, and YAML files, are usually easier to use.
Every configuration implementation, such as XMLConfiguration, YamlConfiguration, JsonConfiguration, etc. has the primary task of converting the configuration text into the Node tree, typically by parsing the text with whatever tool is available for that document type. It should be noted that while most of the supported document types are inherently tree structured, the Java properties syntax is not. Because of the need to convert the syntax into a Node tree the Java properties syntax used by Log4j required all properties follow a naming pattern that made the tree structure clear. As a consequence, the Java Properties format tends to be more verbose than using a different document type.
Log4j has the ability to automatically configure itself during initialization. When Log4j starts it will locate all the ConfigurationFactory plugins and arrange them in weighted order from highest to lowest. As delivered, Log4j contains four ConfigurationFactory implementations: one for JSON, one for YAML, one for properties, and one for XML.
When log4j2.configurationFile references a URL, Log4j will first determine if the URL reference a file using the file protocol. If it does Log4j will validate that the file URL is valid and continue processing as previously described. If it contains a protocol other than file then Log4j will inspect the value of the log4j2.Configuration.allowedProtocols system property. If the provided list contains the protocol specified then Log4j will use the URI to locate the specified configuration file. If not an exception will be thrown and an error message will be logged. If no value is provided for the system property it will default to "https, file, jar". Use of any protocol other than "file" can be prevented by setting the system property value to "_none". This value would be an invalid protocol so cannot conflict with any custom protocols that may be present.
Log4j supports access to remote URLs that require authentication. Log4j supports basic authentication out of the box. If the log4j2.Configuration.username and log4j2.Configuration.password are specified those values will be used to perform the authentication. If the password is encrypted a custom password decryptor may be supplied by specifying the fully qualified class name in the log4j2.Configuration.passwordDecryptor system property. A custom AuthenticationProvider may be used by setting the log4j2.Configuration.authenticationProvider system property to the fully qualified class name of the provider.
As of version 2.4, Log4j now supports configuration via properties files. Note that the property syntax is NOT the same as the syntax used in Log4j 1. Like the XML and JSON configurations, properties configurations define the configuration in terms of plugins and attributes to the plugins.
Prior to version 2.6, the properties configuration requires that you list the identifiers of the appenders, filters and loggers, in a comma separated list in properties with those names. Each of those components will then be expected to be defined in sets of properties that begin with component... The identifier does not have to match the name of the component being defined but must uniquely identify all the attributes and subcomponents that are part of the component. If the list of identifiers is not present the identifier must not contain a '.'. Each individual component MUST have a "type" attribute specified that identifies the component's Plugin type.
As of version 2.17.2, rootLogger and logger.key properties can be specified to set the level and zero or more appender refs to create for that logger. The level and appender refs are separated by comma , characters with optional whitespace surrounding the comma. The following example demonstrates how the shorthand is expanded when reading properties configurations.
A LoggerConfig (including the root LoggerConfig) can be configured with properties that will be added to the properties copied from the ThreadContextMap. These properties can be referenced from Appenders, Filters, Layouts, etc just as if they were part of the ThreadContext Map. The properties can contain variables that will be resolved either when the configuration is parsed or dynamically when each event is logged. See Property Substitution for more information on using variables.
Log4j 2 supports the ability to specify tokens in the configuration as references to properties defined elsewhere. Some of these properties will be resolved when the configuration file is interpreted while others may be passed to components where they will be evaluated at runtime. To accomplish this, Log4j uses variations of Apache Commons Lang's StrSubstitutor and StrLookup classes. In a manner similar to Ant or Maven, this allows variables declared as $name to be resolved using properties declared in the configuration itself. For example, the following example shows the filename for the rolling file appender being declared as a property.
While this is useful, there are many more places properties can originate from. To accommodate this, Log4j also supports the syntax $prefix:name where the prefix identifies tells Log4j that variable name should be evaluated in a specific context. See the Lookups manual page for more details. The contexts that are built in to Log4j are:
Default properties may also be specified in the Lookup by using the syntax $lookupName:key:-defaultValue. In some cases the key might contain a leading '-'. When this is the case an escape character must be included, such as $main:\--file:-app.properties. This would use the MainMapLookup for a key named --file. If the key is not found then app.properties would be used as the default value.
If no value is found for the key in the Lookup associated with the prefix then the value associated with the key in the properties declaration in the configuration file will be used. If no value is found the variable declaration will be returned as the value. Default values may be declared in the configuration by doing:
Maven can run unit and functional tests during the build cycle. By default, any files placed in src/test/resources are automatically copied to target/test-classes and are included in the classpath during execution of any tests. As such, placing a log4j2-test.xml into this directory will cause it to be used instead of a log4j2.xml or log4j2.json that might be present. Thus a different log configuration can be used during testing than what is used in production.
The Log4j documentation references a number of System Properties that can be used to control various aspects of Log4j 2 behavior. The table below lists these properties along with their default value and a description of what they control. Any spaces present in the property name are for visual flow and should be removed.
The following is a list of available global configuration properties. Note that these can only be set once per JVM process unlike configuration settings available in configuration files. The Property Name column contains the name used in properties files and system properties; Environment Variable for the equivalent environment variable; and Legacy Property Name for the pre-2.10 name.
Lately I decided to learn how to use the log4j2 logger. I downloaded required jar files, created library, xml comfiguration file and tried to use it. Unfortunately i get this statement in console (Eclipse) :
Is this a simple eclipse java project without maven etc? In that case you will need to put the log4j2.xml file under src folder in order to be able to find it on the classpath.If you use maven put it under src/main/resources or src/test/resources
Just adding these didn't pick the configuration and always gave error. The way of debugging configuration by adding -Dorg.apache.logging.log4j.simplelog.StatusLogger.level=TRACE helped in seeing the logs. Later had to download the source using Maven and debugging helped in understanding the depended classes of log4j2. They are listed in org.apache.logging.log4j.core.config.yaml.YamlConfigurationFactory:
My appender is called a WindowsEventLogAppender. Any idea what's wrong with my properties file? I see the console test messages but none of the messages from my appender. Right now I'm just doing a System.out.println in my custom appender to verify it's getting called.
You can also refer to log4j2 documentation for configuring multiple conditions. Log4j2 documentation describes XML configuration. However, by referring to these examples, you can think and guess properties configuration also.
following is a modification of original log4j2.properties and section Server JSON in Elasticsearch 7.9.1
It will remove files with extention .gz which modification date is longer than 14 days or if they cumulated size is bigger than 1GB (please replace configuration starting from Delete line)
I have the log4j2.properties file made available as part of the classpath via container image. but its not getting applied. the log level in that log4j2 is set to debug, but i never able to see debug log on serverless batch job. ( on gcloud console or via command : "gcloud dataproc batches wait ***batch-id***"
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