# Logging ### 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. {% hint style="info" %} 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. {% endhint %} ### 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. {% file src="" %} Recommended minimal logging (errors only) {% endfile %} {% file src="" %} Full logging functionality {% endfile %} ### 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 ```bash % java -DKLogInclude=“Started|Ended“ YourApp ``` 
% java -DKLogPropertyFile=/etc/KLog.properties -DKLogLevel=Debug YourApp
{% hint style="warning" %} Please note that all command line options are case sensitive. {% endhint %}
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$$w0rd | | ch.k43.util.KLogJDBCHandler.tablename | Database table name | Table name to be used, e.g. KLOGDATA | | ch.k43.util.KLogJDBCHandler.retensiondays | Number | Number of days to keep log entries, e.g. 14 | | ch.k43.util.KLogJDBCHandler.debug | true, false | Send debug data to standard output (stdout) |
KLog.properties for KLogSMTPHandler | Property Key | Value | Notes | | ----------------------------------------- | --------------------------------------- | ------------------------------------------- | | ch.k43.util.KLogSMTPHandler.mail.from | Sender Address | e.g. | | ch.k43.util.KLogSMTPHandler.mail.to | Recipient Address | e.g. | | h.k43.util.KLogSMTPHandler.mail.subject | Email subject | e.g. "Application Error" | | ch.k43.util.KLogSMTPHandler.smtp.hostname | SMTP hostname | e.g. mail.acme.com | | ch.k43.util.KLogSMTPHandler.smtp.hostport | SMTP port number | e.g. 25 | | ch.k43.util.KLogSMTPHandler.smtp.username | SMTP authentication user name (or none) | e.g. | | ch.k43.util.KLogSMTPHandler.smtp.password | SMTP authentication password (or none) | e.g. Pa$$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 andy.brunner@k43.ch 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 ```java try { ... } catch (Exception e) { KLog.error(e); } ```
Log and Throw RuntimeException ```java try { ... } catch (Exception e) { KLog.abort(e.toString()); } ```
Log and Throw IllegalArgumentException ```java public divide(double arg1, double arg2) { // Check arguments KLog.argException(arg2 == 0.0, "Divisor 0 not allowed"); ... } ```