Appenders : It is used to deliver LogEvents to their destination. It decides what will happen with log information. In simple words, it is used to write the logs in file.
Following are few types of Appenders. Go to LogExpert download folder. Report a Bug. Previous Prev. This is a very easy-to-use Log4J functionality inside Spring applications. The following example will take you through simple steps to explain the simple integration between Log4J and Spring. We assume you already have log4J installed on your machine. We will use only log4j-x. This can cause performance issues if a logger is configured at a level like trace or debug with the expectation that most logs will be filtered on an Appender reference or Appender as Log4j will calculate the location information even though the log event is going to be discarded.
To disable this behavior the includeLocation attribute can be set to false on the LoggerConfig. This will cause Log4j to defer calculating the location information until absolutely necessary. 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. The LoggerConfig may also be configured with one or more AppenderRef elements. Each appender referenced will become associated with the specified LoggerConfig. If multiple appenders are configured on the LoggerConfig each of them be called when processing logging events. Every configuration must have a root logger.
The main differences between the root logger and other loggers are. An appender is configured either using the specific appender plugin's name or with an appender element and the type attribute containing the appender plugin's name. In addition each appender must have a name attribute specified with a value that is unique within the set of appenders. The name will be used by loggers to reference the appender as described in the previous section.
Most appenders also support a layout to be configured which again may be specified either using the specific Layout plugin's name as the element or with "layout" as the element name along with a type attribute that contains the layout plugin's name.
The various appenders will contain other attributes or elements that are required for them to function properly. Although only a single filter element can be configured, that element may be the filters element which represents the CompositeFilter. The filters element allows any number of filter elements to be configured within it. The following example shows how multiple filters can be configured on the ConsoleAppender.
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. 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.
See the Lookups manual page for more details. The contexts that are built in to Log4j are:. A default property map can be declared in the configuration file by placing a Properties element directly after the Configuration element and before any Loggers, Filters, Appenders, etc.
If the value cannot be located in the specified lookup the value in the default property map will be used. The default map is pre-populated with a value for "hostName" that is the current system's host name or IP address and the "contextName" with is the value of the current logging context.
See many places a Properties element is used in this section for examples. In some cases the key might contain a leading '-'. This would use the MainMapLookup for a key named --file. If the key is not found then app.
You could disable message pattern lookups globally by setting system property log4j2. In the previous example the "Routes" element is capable of resolving the variable at runtime. Not all elements support resolving variables at runtime. Components that do will specifically call that out in their documentation. 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:.
As a footnote, it is worth pointing out that the variables in the RollingFile appender declaration will also not be evaluated when the configuration is processed. This is simply because the resolution of the whole RollingFile element is deferred until a match occurs.
See RoutingAppender for more information. Log4j provides support for JSR scripting languages to be used in some of its components. Any language that provides support for the JSR scripting engine may be used. A list of the languages and bindings for them can be found at the Scripting Engine web site. However, some of the languages listed there, such as JavaScript, Groovy and Beanshell, directly support the JSR scripting framework and only require that the jars for that language be installed.
The script element contains a name for the script, the language of the script, and the script text. The scriptFile element contains the name of the script, its location, its language, its charset, and whether the file should be watched for changes.
The name of the script is used to store the script, along with its ScriptEngine, so it can quickly be located each time the script needs to be run.
While the name is not required, providing it will help in debugging problems when the script is running. The language must be provided on the script element and must specify one of the language names that appear in the Configuration status log as described in the next section. If the language is not specified on the scriptFile element the language will be determined by the file extension of the script path.
If file monitoring is requested it will only be enabled if a non-zero monitorInterval is specified on the configuration element. That interval will be used to check for changes in the file.
If the status attribute on the Configuration element is set to DEBUG the list of script engines currently installed and their attributes will be listed. Although some engines may say they are not thread safe, Log4j takes steps to insure that the scripts will run in a thread-safe manner if the engine advertises that it is not thread safe. When the scripts are executed they will be provided with a set of variables that should allow them to accomplish whatever task they are expected to perform.
See the documentation for the individual components for the list of variables that are available to the script. The components that support scripting expect a return value to be passed back to the calling Java code. This is not a problem for several of the scripting languages, but Javascript does not allow a return statement unless it is within a function. However, Javascript will return the value of the last statement executed in the script. As a consequence, code such as that shown below will result in the desired behavior.
JSR scripting engines are supposed to identify that they support the Compilable interface if they support compiling their scripts. Beanshell does this. However, whenever the compile method is called it throws an Error not an Exception. Log4j catches this but will log the warning shown below for each Beanshell script when it tries to compile them. All Beanshell scripts will then be interpreted on each execution. XML configuration files can include other files with XInclude. The Log4j As of Log4j 2.
See Log4j 2 Compatiblity with Log4j 1 for more information. Log4j 2. Some features require optional dependencies; the documentation for these features will specify the required dependencies.
This release contains new features and fixes which can be found in the latest changes report. As its name suggests it uses a template to define the elements to include in the JSON. This Layout was contributed by the author of the log4j2-logstash-layout at GitHub, and who is now a member of the Log4j community. Apache Log4j 2 Apache Log4j 2 is an upgrade to Log4j that provides significant improvements over its predecessor, Log4j 1. Features API Separation The API for Log4j is separate from the implementation making it clear for application developers which classes and methods they can use while ensuring forward compatibility.
Avoid lock-in Applications coded to the Log4j 2 API always have the option to use any SLF4J-compliant library as their logger implementation with the log4j-to-slf4j adapter. Tomcat defines loggers by Engine and Host names. For example, for a more detailed Catalina localhost log, add this to the end of the log4j.
Note that there are known issues with using this naming convention with square brackets in log4j XML based configuration files, so we recommend you use a properties file as described until a future version of log4j allows this convention. This level should be used sparingly when debugging of internal Tomcat operations is required. Your web applications should certainly use their own log4j configuration. This is valid with the above configuration.
You would place a similar log4j. Then specify your package level logging. This page is intended only as a bootstrapping guide. This exposes log4j libraries to the web applications through the Common classloader.
See class loading documentation for details. Because of that, the web applications and libraries using Apache Commons Logging library are likely to automatically choose log4j as the underlying logging implementation. The java. For more information, see the subsections of the Introduction to this page. You should confirm that all your log files are being created by log4j before disabling the standard mechanism. The Access Log Valve and ExtendedAccessLogValve use their own self-contained logging implementation, so they cannot be configured to use log4j.
Refer to Valves for specific configuration details. Notice: This comments section collects your suggestions on improving documentation for Apache Tomcat. If you have trouble and need help, read Find Help page and ask your question on the tomcat-users mailing list. Do not ask such questions here.
The Apache Comments System is explained here. A web application running on Apache Tomcat can: Use any logging framework of its choice. Use system logging API, java. Java logging API — java. Servlets logging API The calls to javax.
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