{"id":1067,"date":"2016-08-29T20:44:48","date_gmt":"2016-08-29T20:44:48","guid":{"rendered":"http:\/\/blog.paranoidprofessor.com\/?p=1067"},"modified":"2016-09-02T18:53:36","modified_gmt":"2016-09-02T18:53:36","slug":"better-logging-than-printf-using-log4j-part-i","status":"publish","type":"post","link":"https:\/\/blog.paranoidprofessor.com\/index.php\/2016\/08\/29\/better-logging-than-printf-using-log4j-part-i\/","title":{"rendered":"better logging than printf – using log4j – part I"},"content":{"rendered":"

The old way<\/h2>\n

Log files or debugging can be done using print statements. \u00a0It is a very rudimentary way to see some of your internal variables or to have a log of how the program run went.<\/p>\n

This printf sample can turn off the debugging with a single variable. \u00a0It is not too difficult\u00a0to set this value as a parameter to the program but it is really just too much effort for such simple control. \u00a0It is a all or nothing that is not so satisfying.<\/p>\n

It is however, much better than not having any ability to log or debug the program in question.<\/p>\n

\n
public class Program  {\r\n\r\n\tboolean debug = true;\r\n\tpublic Program()\r\n\t{\r\n\t}\r\n\tpublic void performWork()\r\n\t{\r\n\t\tint index = 0;\r\n\t\tSystem.out.println(\"Interface 'Program' starting\");\r\n\r\n\t\tfor (index = 1; index <= 10; index++)\r\n\t\t{\r\n\t\t\tint square = index * index;\r\n\t\t\tif (debug == true)\r\n\t\t\t\tSystem.out.println(index + \" x \" + index + \" = \" + square);\r\n\t\t\tSystem.out.println(\"square is \" + square);\r\n\t\t}\r\n\t\tSystem.out.println(\"Interface 'Program' finished\");\r\n\t}\r\n\tpublic static void main(String args[])\r\n\t{\r\n\t\tProgram helper = new Program();\r\n\t\thelper.performWork();\r\n\t}\r\n}<\/code>\r\n<\/pre>\n<\/div>\n
“Printf” logfile output<\/h2>\n
Interface 'Program' starting
\n1 x 1 = 1
\nsquare is 1
\n2 x 2 = 4
\nsquare is 4
\n3 x 3 = 9
\nsquare is 9
\n4 x 4 = 16
\nsquare is 16
\n5 x 5 = 25
\nsquare is 25
\n6 x 6 = 36
\nsquare is 36
\n7 x 7 = 49
\nsquare is 49
\n8 x 8 = 64
\nsquare is 64
\n9 x 9 = 81
\nsquare is 81
\n10 x 10 = 100
\nsquare is 100
\nInterface 'Program' finished<\/code><\/div>\n
<\/div>\n
This output may have been acceptable back in computer class but it really doesn’t measure up in a production environment. \u00a0True, we see the output, both the standard\u00a0and debug output, however,\u00a0this output could have been from version 1 of our program six months ago or version 3 yesterday.<\/p>\n
Fortunately, better logging and debug output has been solved quite elegantly by the Log4j project at Apache<\/a>.<\/p>\n
The really clever thing about their\u00a0solution is that all of the logging\/debugging is controlled via a tiny configuration file. \u00a0Write your program to read in the configuration file and then use the log4j output methods. \u00a0Changing the configuration file changes the nature of the log output.<\/p>\n
The object is “Logger” has a few methods each of which can be used in lieu of printf.<\/p>\n