Manual

Introduction

CustomAppender works by simply invoking a specified method with the formatted log message to be handled however you want. The method can be static or you can specify the instance to use.

A manual on how to use Log4j2 can be found here.

Attributes

Attribute	Required	Type	Description
`name`	x	`String`	The name of the appender.
`class`	x	`String`	The full name of the class where either the `appendInstance`, if specified, or the `append` is located.
`append`		`String`	The name of the method that will be invoked when a message should be logged. The return type should be `void` and should accept 1 `String` parameter. If an `appendInstance` is not specified, this method should be static. If not specified, this will default to `"append"`.
`appendInstance`		`String`	The name of the static method that will return the instance where `append` will be invoked. The method should return an object of any type and have no parameters.
`cacheInstance`		`boolean`	If `false`, it will reacquire the instance from `appendInstance` every time `append` is invoked. If `appendInstance` is not specified, this has no effect. It defaults to `true`.
`ignoreExceptions`		`boolean`	If `false`, exceptions while appending events will be propagated to the caller. If `true`, exceptions will instead be internally logged and then ignored. It defaults to `true`.

You can also include Filters and Layouts.

Examples

Without `appendInstance`

This example will simply output the log message to the console.

log4j2.xml:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN" packages="com.frostphyr.custom">
	<Appenders>
		<Custom name="Console" class="com.frostphyr.custom.test.ConsoleAppender">
			<PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
		</Custom>
	</Appenders>
	<Loggers>
		<Root level="ALL">
			<AppenderRef ref="Console"/>
		</Root>
	</Loggers>
</Configuration>

ConsoleAppender.java:

package com.frostphyr.custom.test;

public class ConsoleAppender {
	
	public static void append(String message) {
		System.out.println(message);
	}

}

With `appendInstance`

This example will use Swing and insert the log message into a JTextArea. log4j2.xml:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN" packages="com.frostphyr.custom">
	<Appenders>
		<Custom name="Swing" class="com.frostphyr.custom.test.SwingAppender" append="appendTextArea" appendInstance="getInstance">
			<PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
		</Custom>
	</Appenders>
	<Loggers>
		<Root level="ALL">
			<AppenderRef ref="Swing"/>
		</Root>
	</Loggers>
</Configuration>

SwingAppender.java:

package com.frostphyr.custom.test;

import javax.swing.JTextArea;
import javax.swing.SwingUtilities;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;

public class SwingAppender {
	
	private static SwingAppender instance = new SwingAppender();
	
	public static SwingAppender getInstance() {
		return instance;
	}
	
	private JTextArea textArea = new JTextArea();
	
	public void appendTextArea(String text) {
		SwingUtilities.invokeLater(() -> {
			Document doc = textArea.getDocument();
			try {
				doc.insertString(doc.getLength(), text, null);
			} catch (BadLocationException e) {
			}
		});
	}

}

Alternatively, instead of having a singleton in SwingAppender, the instance can be retrieved from another class. For example, in the main class:

package com.frostphyr.custom.test;

public class LoggerTest {
	
	private static SwingAppender swingAppender = new SwingAppender();

	public static void main(String[] args) {
		//Do stuff
	}
	
	public static SwingAppender getSwingAppender() {
		return swingAppender;
	}

}

log4j2.xml would then look like:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN" packages="com.frostphyr.custom">
	<Appenders>
		<Custom name="Swing" class="com.frostphyr.custom.test.LoggerTest" append="appendTextArea" appendInstance="getSwingAppender">
			<PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
		</Custom>
	</Appenders>
	<Loggers>
		<Root level="ALL">
			<AppenderRef ref="Swing"/>
		</Root>
	</Loggers>
</Configuration>