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-
log4javascript quick start tutorial
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Three step guide
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- -
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Download the code
-
- Unzip the distribution and copy log4javascript.js into the desired
- location. No other files are necessary.
-
-
- -
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Initialize log4javascript in your web page
-
- Include log4javascript.js in your page using the code below. This
- code assumes log4javascript is stored in the same directory as
- your web page.
-
-
-<script type="text/javascript" src="log4javascript.js"></script>
-<script type="text/javascript">
- var log = log4javascript.getDefaultLogger();
-</script>
-
-
- The default logger uses a PopUpAppender
- which opens a pop-up window. By default, this window will open when the first
- log message is written. For this to work, you will need to disable any pop-up blockers
- you may have.
-
-
- -
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Include logging statements in your code
-
- You have six logging methods at your disposal, depending on the severity
- of the message you wish to log. By default, all messages are logged
- in the pop-up window. The logging methods are:
-
-
- log.trace(message[, message2, ... ][, exception])log.debug(message[, message2, ... ][, exception])log.info(message[, message2, ... ][, exception])log.warn(message[, message2, ... ][, exception])log.error(message[, message2, ... ][, exception])log.fatal(message[, message2, ... ][, exception])
-
- And that's it, log away. Below are some examples of common types of logging.
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Logging examples
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- -
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A simple logging message string
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- log.info("Hello world");
-
-displays
-
-19:52:03 INFO - Hello world
-
-
- -
-
Logging an error with a message
-
- try {
- throw new Error("Faking something going wrong!");
- } catch (e) {
- log.error("An error occurred", e);
- }
-
-displays
-
-19:52:32 ERROR - An error occurred
-Exception: Faking something going wrong! on line number 80 in file basic.html
-
-
- -
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Logging multiple messages with one logging call
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- var a = "Hello";
- var b = 3;
- log.debug(a, b);
-
-displays
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-19:53:05 DEBUG - Hello 3
-
-
- -
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Logging an object
- Logging an object:
-
- var obj = new Object();
- obj.name = "Octopus";
- obj.tentacles = 8;
- log.info(obj);
-
-displays
-
-19:53:17 INFO - {
- name: Octopus,
- tentacles: 8
-}
-
-
-
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Tweaking the default logger
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- The default logger is fine as a starting point, but what if you want the default logger
- with a few different options (say, bringing the pop-up to the front whenever a log message is
- logged, or having new log messages appear at the top of the pop-up rather than the bottom)?
-
-
- In this case, you will need to create a new logger, then create a
- PopUpAppender, set options
- on it, and add it to the logger:
-
-
-<script type="text/javascript" src="log4javascript.js"></script>
-<script type="text/javascript">
- // Create the logger
- var log = log4javascript.getLogger();
-
- // Create a PopUpAppender with default options
- var popUpAppender = new log4javascript.PopUpAppender();
-
- // Change the desired configuration options
- popUpAppender.setFocusPopUp(true);
- popUpAppender.setNewestMessageAtTop(true);
-
- // Add the appender to the logger
- log.addAppender(popUpAppender);
-
- // Test the logger
- log.debug("Hello world!");
-</script>
-
-
- See this example in action (opens in new window)
-
-
- Refer to the manual for more information about
- configuring appenders and more
- details about PopUpAppender.
-
-
Sending log messages to the server
-
- For this you will need to use an AjaxAppender
- as follows:
-
-
- var ajaxAppender = new log4javascript.AjaxAppender(URL);
- log.addAppender(ajaxAppender);
-
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- Now your log messages will appear in the pop-up window and be sent
- asynchronously to the URL you specify in the form of HTTP post parameters.
- No server-side code to process these requests is provided with log4javascript.
-
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- See AjaxAppender for more details
- on formatting log messages.
-
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Changing the format of log messages
-
- Using a Layout, you can
- format log messages however you like. For example:
-
-
- var log = log4javascript.getLogger("mylogger");
- var popUpAppender = new log4javascript.PopUpAppender();
- var layout = new log4javascript.PatternLayout("[%-5p] %m");
- popUpAppender.setLayout(layout);
-
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A call to
-
- log.debug("Hello world");
-
-
will now result in output in the pop-up window of
-
-[DEBUG] Hello world
-
-
- See PatternLayout for more details
- on formatting log messages.
-
-