See also
- log4j
- Chainsaw (log file viewer)
- commons-logging on GitHub
| Developer(s) | Apache Software Foundation |
|---|---|
| Stable release | 1.2 / July 2014 |
| Repository | github |
| Written in | Java |
| Operating system | Cross-platform |
| Type | Logging Tool |
| License | Apache License 2.0 |
| Website | commons |
Apache Commons Logging (previously known as Jakarta Commons Logging or JCL) is a Java-based logging utility and a programming model for logging and for other toolkits. It provides APIs, log implementations, and wrapper implementations over some other tools. [1] [2] [3]
The following table defines the log levels and messages in Apache Commons Logging, in decreasing order of severity. The left column lists the log level designation in and the right column provides a brief description of each log level.
| Level | Description |
|---|---|
| fatal | Severe errors that cause premature termination. Expect these to be immediately visible on a status console. |
| error | Other runtime errors or unexpected conditions. Expect these to be immediately visible on a status console. |
| warn | Use of deprecated APIs, poor use of API, 'almost' errors, other runtime situations that are undesirable or unexpected, but not necessarily "wrong". Expect these to be immediately visible on a status console. |
| info | Interesting runtime events (startup/shutdown). Expect these to be immediately visible on a console, so be conservative and keep to a minimum. |
| debug | Detailed information on the flow through the system. Expect these to be written to logs only. |
| trace | Most detailed information. Expect these to be written to logs only. |
Two basic abstractions, Log and LogFactory, are used in Apache Commons Logging. [3]
Sample code may look like as follows:
packagecom.cascadetg.ch09;importorg.apache.commons.logging.Log;importorg.apache.commons.logging.LogFactory;importorg.apache.commons.logging.impl.Jdk14Logger;publicclassLogGenerator{// Note that you pass in an instance of this class to the// log generator. This allows you to find the messages// generated by this class.privatestaticLoglog=LogFactory.getLog(LogGenerator.class);publicstaticvoidconfigJDKLogger(){try{((Jdk14Logger)log).getLogger().setLevel(java.util.logging.Level.ALL);((Jdk14Logger)log).getLogger().addHandler((java.util.logging.FileHandler)Class.forName("java.util.logging.FileHandler").newInstance());System.out.println("Added JDK 1.4 file handler");}catch(Exceptione){System.out.println("Unable to load JDK 1.4 logging.");e.printStackTrace();}}publicstaticvoidmain(String[]args){configJDKLogger();System.setErr(System.out);System.out.println();System.out.println("Test fatal log");try{Stringfoo=null;intx=0/(newInteger(foo)).intValue();}catch(Exceptione){log.fatal(e.getMessage(),e);}System.out.println();System.out.println("Test error log");try{Objectfoo=null;foo.toString();}catch(Exceptione){log.error(e.getMessage(),e);}System.out.println();System.out.println("Test warn log");try{Class.forName("com.cascadetg.NonexistantClass");}catch(Exceptione){log.warn("Can't find a non-existent class!");}System.out.println();System.out.println("Test info log");log.info("Starting app!");log.info("Quitting app!");System.out.println();System.out.println("Test debug log");if(1>2){log.debug("1 > 2 evaluated true");if(10%2==0)log.debug("10 % 2 is 0");elselog.debug("10 % 2 is not 0");}else{log.debug("1 > 2 evaluated false");}System.out.println();System.out.println("Test trace log");log.trace("Calling trace method.");log.trace("Calling trace method.");log.trace("Calling trace method.");log.trace("Calling trace method.");log.trace("Calling trace method.");System.out.println();System.out.println("Log test complete.");}}Java Platform, Standard Edition is a computing platform for development and deployment of portable code for desktop and server environments. Java SE was formerly known as Java 2 Platform, Standard Edition (J2SE).
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