Although this article is short but the general developer is already enough, the application process of Log4j in JBuilder and Eclipse is described in the text, and it is a very good start. I believe.
1 Overview
Log4j is a log4 family member, a log4 family package: Look at 4 The letter knows which environment and the API developed. The log4j we want to introduce is of course an API developed for Java.
Log4 family
Log4c
Suitable for c
LOG4CPLUS / LOG4CPP
Suitable for C
Log4j
Suitable for Java
Log4net
Suitable for DOTNET
Log4perl
Suitable for Perl
Log4PHP
Suitable for PHP
Log4plsql
Suitable for PL / SQL
Log4ls
Suitable for LotusScript log4py / log4p
Suitable for python qmmslog
Suitable for QT / C platforms
Log4R
Suitable for Ruby JDK1.4's Util.logging Framework
Suitable for JDK1.4UTIL
We omitted the long-term big interlass for log4j, briefly summarizes its role: it is the output interface of the application log, the output format, and output location can be used during development, and can be used during operation. The log category mainly:
Log class
Debug
Debugging information
Info
General information
Warn
Warning information
Error
Error message
Fatal
Severe error message
That is, you can define the type of output log based on these levels. We still go directly to how to use, don't talk too much theory.
2, download log4j
The download address is: http://logging.apache.org/site/binindex.cgi, the highest version available is:
JAKARTA-LOG4J-1.2.8, there are different packages, such as the Windows platform: jakarta-log4j-1.2.8.zip, find: jakarta-log4j-1.2.8 / dist / lib directory log4j- 1.2.8.jar file, this is the JAR file we have to use, and other documents are temporarily restless. Copy this file to the specified location, such as D: / lib directory. (We will add this file in the application engineering).
3, create an app in JBuilder
Procedure can refer to other information
4, add log4j-1.2.8.jar to JBuilder project
4.1 Establish "User Home" library (as an example of JBuilder9 trial version)
Click on the menu [Tools] - [Configure Libraries] to open the Library File Design dialog box, select "User Home" in the tree directory, click the [New ....] Button, pop up the Configuration dialog box, enter log4jlib in the "Name" position, then Click the [Add ....] Button, navigate through the directory tree to the directory where the log4j-1.2.8.jar is located, such as a D: / lib directory, select Log4j-1.2.8.jar, click 3 times [OK] back to jBuilder Main interface. This way you have established a library file. Let JBuilder can use the latest version of Log4j. In fact, in the advanced JBUILDER version already contains the library file of log4j, that is, this step can be omitted.
4.2, add library file reference to the project
Right-click the project name in JBuilder's "Project" dialog box, select "Properties" in the pop-up POP menu, open the Engineering Properties dialog, select the [Paths] tag - [Required Libraries] tab - [Add ....] Button, Select "log4jlib" and click 2 [ok] to return to the main interface of JBuilder, so that the project adds library file reference. 5, log4j output format definition
Log4j's format definition is defined by a ".properties" file, which defines a lot of elements regarding the digital formats and output locations, see the case where the following example is (the example in log4j.properties). Switch log4j.rootlogger = debug, b1 of B1 or A1, and comment different locations, implement log output to file or console. Place this log4j.properties file is placed in the topic of the project (with the .jpx file in the same directory).
Log4j.properties content:
Log4j.rootlogger = debug, b1 # Print to file # log4j.Appender.a1 = org.apache.log4j.rollingfileAppender # log4j.Appender.a1.file = example.log # log4j.Appender.a1.maxfilesize = 100KB # log4j. appender.a1.maxbackupindex = 1 # log4j.Appender.a1.Layout = org.apache.log4j.patternLayout # log4j.Appender.a1.Layout.conversionPattern =% 5P [% T] (% F:% L) -% M % N
# Print to the console log4j.Appender.b1 = org.apache.log4j.consoleappender log4j.Appender.b1.Layout = Org.apache.log4j.patternLayout log4j.Appender.b1.Layout.conversionPattern =% - 4R% -5p [ % T]% 37C% 3X -% m% n log4j.Appender.b1.Layout.conversionPattern =% 5P [% T] (% F:% L) -% M% N
6, use log4j in the Java class file
6.1, IMPORT needs package file
Import org.apache.log4j. *; Place this statement on the IMPORT position of the file.
6.2, define the logger object
Static logger logger = logger.getlogger (frame1.class.getname ()); defines this object where the program declared variables and is a static object. Where Frame1 is the name of your current class.
6.3, load attribute file
PropertyConfigurator.configure ("log4j.properties"); fill in this statement at the beginning of the Jbinit () method, load the properties file.
6.4, you can use anywhere
Input similar to where logging is required
Logger.info ("Log Information");
Logger.warn ("Log Information");
Logger.debug ("Log Information");
Logger.fatal ("Log Information");
Logger.Error ("Log Information");
such as:
/ ** * Main Factory component initialization * @throws java.lang.exception * / private void jbinit () throws exception {propertyConfigurator.configure ("log4j.properties"); logger.info (Logonuser "initialization start"); // logonuser is the user name of the landing system ................ ................... ................ logger.info (Logonuser "initialization end");} The output result is:
INFO [AWT-EventQueue-0] - Admin Initialization Start INFO [AWT-EventQueue-0] (MainFrame.java: 1013) - ADMIN initialization end
Here, we have completed the log4j application process in JBuilder, and the format of the output log is not very neat, the process of outputting the test of the file, just changed in log4j.properties:
Log4j.properties content:
log4j.rootLogger = debug, A1 # Print to File log4j.appender.A1 = org.apache.log4j.RollingFileAppender log4j.appender.A1.File = example.log log4j.appender.A1.MaxFileSize = 100KB log4j.appender.A1. MaxBackupindex = 1 log4j.appender.a1.Layout = org.apache.log4j.patternLayout log4j.Appender.a1.Layout.conversionPattern =% 5P [% T] (% F:% L) -% M% N
# Print to the console # log4j.Appender.b1 = org.apache.log4j.consolerappender # log4j.appender.b1.Layout = org.apache.log4j.patternlayout # log4j.Appender.b1.Layout.conversionPattern =% - 4R% -5P [% T]% 37C% 3X -% M% N # log4j.Appender.b1.Layout.conversionPattern =% 5P [% T] (% F:% L) -% M% N
Log4j will create an Example.log file in places with log4j.properties, and log information. When the size of the file is greater than 100KB, log4j creates a new EXAMPLE.LOG file, back up the Example.log file. The number of backup files depends on the MaxBackupIndex property.
Next section We introduce the application process of log4j on Eclipse
7, add log4j-1.2.8.jar to Eclipse
7.1, introduced when new Java projects
The first case is the second step in the second step in the new Java project (add external jar (x)] - select log4j-1.2.8.jar, click [Open] Back to New Engineering Second Step , Click to complete. This introduces the required library file.
7.2, to the existing project, add log4j-1.2.8.jar
If the project already exists, by right-click Project Name - [Properties] - [Java Build Path] - [Add External JAR (X)] - Select Log4j-1.2.8.jar, click [Open] Back to New Engineering Properties - [OK] will go to the interface of the project. 7.3, import log4j.properties file
Through the import function of the project, import the log4j.properties file directly to the most high-level directory of the project. Other steps are 6.1-6.4
7.4, an ordinary application structure is as follows:
/ *
* CREATED ON 2004-10-10
* /
Package com.log4j;
Import org.apache.log4j. *;
/ **
* @Author jem.lee
* /
Public class mylogtest {
Static logger logger = logger.getlogger (MyLogtest.class.getname ());
Public static void main (String [] args) {
PropertyConfigurator.configure ("log4j.properties");
MyLogtest.logger.info ("Test Information Start");
MyLogtest.logger.info ("Test Information End");
}
}
Output results:
INFO [main] (myLogtest.java: 16) - Test information start
INFO [main] (myLogtest.java: 17) - the end of the test information
8, summary
Using the log4j can realize the output of the log record, in fact, many applications will bring a log management module, how to fully utilize the log is also a systematic characteristics, the way you develop log class features and operations may be better than log4j, but I believe you Most of it is impossible, it is better to use the ready-made API, the efficiency is improved, the standard is neat, everything is fine.
