webapp-slf4j-logger

This is a simple logger with minimal configuration. It is an SLF4J backend that forwards logs to a ServletContext object.

All log messages are logged using ServletContext#log.

Features:

• zero-config for default functional behaviour, with HTTP request IP address as log line prefix
• Custom format, supporting mapped diagnostic contexts
• Support for serialization and deserialization

Configuration

Inclusion in a 3.0+ webapp

If your J2EE container is complient with the 3.0+ servlet API, then you just have to include webapp-slf4j-logger.jar in your WEB-INF/lib directory.

You must just make sure that the <web-app> root tag of your web.xml doesn't set metadata-complete=true, otherwise refer to .

Log level

The logging level can be set with a context parameter. Possible values are (case insensitive) trace, debug, info, warn, error, following the standard slf4j levels.

<context-param>
  <param-name>webapp-slf4j-logger.level</param-name>
  <param-value>debug</param-value>
</context-param>

The default enabled level is INFO.

Format

The format can be specified with a context parameter, as a sequence of placeholders and literal text.

<context-param>
  <param-name>webapp-slf4j-logger.format</param-name>
  <param-value>%logger [%level] [%ip] %message</param-value>
</context-param>

Placeholders begin with '%' and must only contain alpha-numeric characters.

Predefined placeholders:

• %date - the timestamp, formatted as "YYYY-MM-DD HH:mm:ss,sss"
• %level, %Level, %LEVEL - the level in lowercase, standard case or uppercase (and left-padded to five characters)
• %logger - the name of the logger
• %ip - the IP address of the current request
• %message - the actual log message string

Custom placeholders must correspond to existing MDC tags. For instance, to see IPs of each log line's request, you can use the provided com.republicate.slf4j.helpers.IPFilter, and set up a format with the %ip placeholder.

The default format is: %logger [%level] [%ip] %message (it doesn't include %date, as the date will usually be added by the J2EE container, nor does it add a terminal \n, as the container will take care of it).

Email notifications

The logger can be configured to send an email if severity is beyond a certain level (typically, warning or error). The configuration parameter is of the form: level:protocol:mail_server:port:from_address:to_address The only protocol supported for now is smtp.

Example:

<context-param>
  <param-name>webapp-slf4j-logger.notification</param-name>
  <param-value>warn:smtp:mail.server:25:from@address:to@address</param-value>
</context-param>

Inclusion in a maven-based project

Declare a dependency on webapp-slf4j-logger:

<dependency>
  <groupId>com.republicate</groupId>
  <artifactId>webapp-slf4j-logger</artifactId>
  <version>1.0.0</version>
</dependency>

Inclusion in a non-3.0+ webapp

If your J2EE container is not complient with servlet API 3.0+, or if you want to use metadata-complete=true in a 3.0+ application to speed up its restart, you have to add to web.xml:

<listener>
  <listener-class>com.republicate.slf4j.impl.ServletContextLoggerSCL</listener-class>
</listener>

And if you want to enable the %ip format tag, you'll also have to add the following filter:

<filter>
  <filter-name>webapp-slf4j-logger-ip-tag-filter</filter-name>
  <filter-class>com.republicate.slf4j.impl.IPTagFilter</filter-class>
</filter>

with its mapping:

<filter-mapping>
  <filter-name>webapp-slf4j-logger-ip-tag-filter</filter-name>
  <url-pattern>/*</url-pattern>
  <dispatcher>REQUEST</dispatcher>
  <dispatcher>FORWARD</dispatcher>
</filter-mapping>

FAQ

All other SLF4J jars begin with "slf4j". Why isn't this library called slf4j-webapp-logger?

Some containers, Tomcat at least, will not search for servlet-3.0 annotations in a certain number of jars, among which all slf4j-* jars...