📖Logging

Add precise timing and exact code location to your logging data.

KLog Class Overview

• Built on Standard Java Logging Utilizes the built-in java.util.logging framework, part of Java SE. No additional external libraries, such as Apache Log4j, are required.

• High Performance Capable of logging over 10,000 lines per second on a MacBook Pro when using the FileHandler and KLogLineFormatter.

• Simplified Logging Streamlines logging with straightforward methods for debug, error, and info messages.

• Static Methods All methods are static, eliminating the need for instantiation.

• Flexible Handlers and Formatters Includes handlers and formatters for generating log output in various formats: tabular text, CSV, XML, JSON, and YAML. Supports sending logs to JDBC-compliant databases or routing error logs to any SMTP server.

• Enhanced Log Details Provides precise timestamps and exact code locations in formatted log outputs.

• Configuration and Runtime Adjustments Logging is enabled via the KLog.properties configuration file, which must be located in the current directory or set thru the startup parameter KLogPropertyFile. Logging levels can dynamically be adjusted and log entries may be filtered at runtime.

The Java utility package uses KLog internally to assist with problem determination. Setting the log level to FINEST in the KLog.properties file enables detailed debugging mode, providing comprehensive insights during code execution.

Logging Handlers

In addition to the standard logging handlers for console and file output, KLog provides the additional classes:

• KLogJDBCHandler: Write each log entry to any JDBC compliant database

• KLogSMTPHandler: Send error log entries (FATAL logging level) to any SMTP server

Logging Formatters

The log information (timestamp, logging level, code location and message) can be formatted with the additional formatter classes:

• KLogCSVFormatter: Format each log entry as a one-line CSV string

• KLogJSONFormatter: Format each log entry as a multi-line JSON string

• KLogLineFormatter: Format each log entry as a one-line tabular string

• KLogXMLFormatter: Format each log entry as a multi-line XML string

• KLogYAMLFormatter: Format each log entry as a multi-line YAML string

Sample Properties Files

The logging properties file enables and configures the logging framework used by all KLog methods. Simply download, edit and and place it in the current directory of your application.

1KB

KLog.properties.minimal.zip

archive

Recommended minimal logging (errors only)

2KB

KLog.properties.sample.zip

archive

Full logging functionality

Special Properties

Startup System Properties

Command Line Option	Default	Purpose
-DKLogPropertyFile	"Klog.properties"	Path and file name of KLog properties file
-DKLogLevel	Set by the KLog properties file	Override KLog level to Info, Error, Debug or Off
-DKLogInclude	Set by the KLog properties file	Limit log entries to specified RegEx match, e.g. “password“
-DKLogExclude	Set by the KLog properties file	Exclude log entries matching RegEx, e.g. “started|ended“

Examples

% java -DKLogInclude=“Started|Ended“ YourApp

% java -DKLogPropertyFile=/etc/KLog.properties -DKLogLevel=Debug YourApp

Please note that all command line options are case sensitive.

Common KLog Properties

Property Key	Value	Notes
ch.k43.util.KLog.level	FINEST, INFO, SEVERE, OFF	Corresponds to KLog logging levels Debug, Info, Error, Off
ch.k43.util.KLog.exclude	RegEx Pattern	Exclude matching log entries, e.g. “password“
ch.k43.util.KLog.include	RexEx Pattern	Include only matching log entries, e.g. “started|ended“

KLog.properties for KLogJDBCHandler

Property Key	Value	Notes
ch.k43.util.KLogJDBCHandler.jdbc.driver	JDBC Driver Class	Java class name, e.g. org.h2.Driver
ch.k43.util.KLogJDBCHandler.jdbc.url	Connection URL	e.g. jdbc:h2:mem:mydb
ch.k43.util.KLogJDBCHandler.jdbc.username	Connection user name	e.g. johnsmith
ch.k43.util.KLogJDBCHandler.jdbc.password	Connection password	e.g. Pa$$w0rd
ch.k43.util.KLogJDBCHandler.tablename	Database table name	Table name to be used, e.g. KLOGDATA
ch.k43.util.KLogJDBCHandler.retensiondays	Number	Number of days to keep log entries, e.g. 14
ch.k43.util.KLogJDBCHandler.debug	true, false	Send debug data to standard output (stdout)

KLog.properties for KLogSMTPHandler

Property Key	Value	Notes
ch.k43.util.KLogSMTPHandler.mail.from	Sender Address	e.g. [e-mail]
ch.k43.util.KLogSMTPHandler.mail.to	Recipient Address	e.g. [e-mail]
h.k43.util.KLogSMTPHandler.mail.subject	Email subject	e.g. "Application Error"
ch.k43.util.KLogSMTPHandler.smtp.hostname	SMTP hostname	e.g. mail.acme.com
ch.k43.util.KLogSMTPHandler.smtp.hostport	SMTP port number	e.g. 25
ch.k43.util.KLogSMTPHandler.smtp.username	SMTP authentication user name (or none)	e.g. [e-mail]
ch.k43.util.KLogSMTPHandler.smtp.password	SMTP authentication password (or none)	e.g. Pa$$w0rd
ch.k43.util.KLogSMTPHandler.smtp.tls	true, false	Use TLS or Non-TLS connection
ch.k43.util.KLogSMTPHandler.threshold	Number	Maximum number of email sent per minute
ch.k43.util.KLogSMTPHandler.debug	true, false	Send debug data to standard output (stdout)

KLog.properties for KLogCSVFormatter

Property Key	Value	Notes
ch.k43.util.KLogCSVFormatter.writeheader	true, false	Add header lines with column names

Examples

Code and Output

KLog.info("Program started");
		
int rc = -1;
KLog.error(rc != 0, "Return code is {}", rc);
	
KLog.debug("Just a debug message");
		
Exception e = new Exception("Program error");
KLog.error(e);
		
KLog.info("Program ended");

2024-08-29T15:49:27.867 D main[1]:ch.k43.util.KLog:open:462                            ===== Application started 2024-08-29T15:49:27.850 =====
2024-08-29T15:49:27.867 D main[1]:ch.k43.util.KLog:open:464                            Java Utility Package (Freeware) ch.k43.util Version 2024.08.29
2024-08-29T15:49:27.868 D main[1]:ch.k43.util.KLog:open:467                            Homepage java-util.k43.ch - Please send any feedback to [e-mail]
2024-08-29T15:49:27.889 D main[1]:ch.k43.util.KLog:open:469                            Host ab-macbook-pro (10.0.0.105)
2024-08-29T15:49:27.889 D main[1]:ch.k43.util.KLog:open:470                            OS platform Mac OS X (Version 14.6.1/aarch64)
2024-08-29T15:49:27.889 D main[1]:ch.k43.util.KLog:open:471                            Java version 17 (OpenJDK 64-Bit Server VM - Eclipse Adoptium)
2024-08-29T15:49:27.891 D main[1]:ch.k43.util.KLog:open:475                            Java heap maximum 16.00 GB, current 1.00 GB, used 4.80 MB, free 1019.20 MB
2024-08-29T15:49:27.891 D main[1]:ch.k43.util.KLog:open:479                            Java locale de/CH, local time UTC +02:00
2024-08-29T15:49:27.891 D main[1]:ch.k43.util.KLog:open:482                            Java classpath ../bin/:../lib/org.json.20230618.jar:../lib/jakarta-mail-1.6.7.jar
2024-08-29T15:49:27.891 I main[1]:Test:main:10                                         Program started
2024-08-29T15:49:27.892 E main[1]:Test:main:13                                         ===> Return code is -1
2024-08-29T15:49:27.892 D main[1]:Test:main:15                                         Just a debug message
2024-08-29T15:49:27.892 E main[1]:Test:main:18                                         ===> java.lang.Exception: Program error
2024-08-29T15:49:27.892 E main[1]:Test:main:18                                         ===> Stack[1]: Test.main(Test.java:17)
2024-08-29T15:49:27.892 I main[1]:Test:main:20                                         Program ended

Log Exception

try {
   ...
} catch (Exception e) {
   KLog.error(e);
}

Log and Throw RuntimeException

try {
  ...
} catch (Exception e) {
  KLog.abort(e.toString());
}

Log and Throw IllegalArgumentException

public divide(double arg1, double arg2) {
  // Check arguments
  KLog.argException(arg2 == 0.0, "Divisor 0 not allowed");
  ...
}