'Logging'에 해당되는 글 12건

Architecture

1. Logger, Appenders and Layouts

Logback is built upon three main classes: Logger, Appender, Layout. These three types of components work together to enable developers to log messages according to message type and level, and to control at runtime how these messages are formatted and where they are reported

Logger  

- It is part of the logback-classic module

Appender, Layout

- These are part of logback-core

2. Printing methods and the basic selection rule

The printing method determines the level of a logging request. For example, if L is a logger instance, then the statement L.info("..") is a logging statement of level INFO.

Basic Selection Rule

A log request of level p issued to a logger having an effective level q, is enabled if p >= q

3. Parameterized logging

FirstStep

1. Requirements

- Logback-classic module requires the presence of slf4j-api.jar and logbacl-core.jar in addition to logback-classic.jar on the classpath

- Launching the HelloWorld application will output a single line on the console. By virtue of logback's default configuration policy, when no default configuration file is found, logback will add a ConsoleAppender to the root logger

- logback can report information about its internal state using a built-in status system

2. Internal state 

- logback will automatically print its internal state on the console

2_1. enable logging requirement

1) Configure the logback environment. You can do so in several more or less sophisticated ways. More on the later

2) In every class where you with to perform logging, retrieve a Logger instance by invoking the org.slf4j.LoggerFactory class' getLogger() method, passing the current class name or the class itself as a parameter

3) Use the logger instance by invoking its printing methods, namely the debug(), info(), warn()and error() methods, This will produce logging output on the configured appenders

Define

- Logback is intended as a successor to the popular log4j project

Logback's architecture is sufficiently generic so as to apply under different circumstances. At present time, logback is divided into three modules,

1. logback-core

- The logback-core module lays the groundwork for the other two modules

2. logback-classic

- The logback-class module can be assimilated to a significantly improved version of log4j

- The logback-class natively implements the SLF4J API so that you can readily switch back and forth between logback and other logging framework such as log4j of java.util.logging

3. logback-access

- The logback-access module integrates with Servlet containers, such as Tomcat and Jetty to provide HTTP-access log functionality

What is the slf4j

1. Define

- The Simple Logging Facade for Java (SLF4J) serves as a simple facade or abstraction for various logging framework(java.util.logging, logback, log4j..) allowing the end user to plug in the desired logging framework at deployment time

2. Install

- http://www.slf4j.org/download.html

- slf4j-api-1.7.21

3. Hello world

3_1. Warning

- The warning is printed because no slf4j binding could be found on your class path

- The warning will disappear as soon as you add a binding to your class path. Assuming you add slf4j-simple-1.7.21.jar so that your class path contains

4. Typical usage pattern

5. Binding with a logging framework at deployment time

- SLF4J supports various logging frameworks. The SLF4J distribution ships with several jar files referred to as 'SLF4J binding', with each binding corresponding to a supported framework

5_1. To switch logging frameworks

Just replace slf4j bindings on your class path.

* For example

To switch from java.util.logging to log4j, just replace slfj-jdk14-1.7.21 jar with slf-j4-log4j12-1.7.21.jar