src/site/xdoc/docs/renderers.xml - logging-log4php - Git at Google

 <?xml version="1.0" encoding="UTF-8"?>
 <!--
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  distributed under the License is distributed on an "AS IS" BASIS,
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 <document xmlns="http://maven.apache.org/XDOC/2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 	xsi:schemaLocation="http://maven.apache.org/XDOC/2.0 http://maven.apache.org/xsd/xdoc-2.0.xsd">

 	<properties>
 		<title>Renderers</title>
 	</properties>

 	<body>
 		<section name="Renderers">
 			<p>Apache log4php can log more than just string messages. If you try to log an object it will be converted
 			to a string and logged. The component which converts Objects to strings in log4php is called a
 			<em>renderer</em>.</p>

 			<subsection name="Default renderer">

 				<p>For example, let's say that an application uses a Person object, like this one:</p>

 <pre class="prettyprint linenums"><![CDATA[
 class Person {
     public $firstName;
     public $lastName;
     public $age;
 }
 ]]></pre>

 				<p>If you try logging it:</p>

 <pre class="prettyprint linenums"><![CDATA[
 $person = new Person();
 $person->firstName = 'John';
 $person->lastName = 'Doe';
 $person->age = 37;

 $logger = Logger::getLogger('main');
 $logger->info("Here comes the person:");
 $logger->info($person);
 ]]></pre>
 				<p>Log4php will render it using the default renderer and you will end the output will look something
 				like:</p>

 <pre class="prettyprint linenums"><![CDATA[
 INFO - Here comes the person:
 INFO - Person Object
 (
     [firstName] => John
     [lastName] => Doe
     [age] => 37
 )
 ]]></pre>

 			</subsection>

 			<subsection name="Creating a custom renderer">
 				<p>In order to make log4php log the Person object in a more readable format, a custom renderer
 				class can be defined which will convert Person objects to a string suitable for logging.</p>

 				<p>Let's call this renderer class PersonRenderer.</p>

 <pre class="prettyprint linenums"><![CDATA[
 /** All renderers must implement the LoggerRenderer interface. */
 class PersonRenderer implements LoggerRenderer {
     public function render($person) {
         return "{$person->firstName} {$person->lastName} ({$person->age})";
     }
 }
 ]]></pre>

 				<p>Now log4php has to be configured to use PersonRenderer for rendering Person objects. This is done
 				in the configuration file.</p>

 				<div class="auto-tabs">
 					<ul>
 						<li>XML</li>
 						<li>PHP</li>
 					</ul>

 					<div class="tab-content">
 						<div class="tab-pane">
 <pre class="prettyprint linenums"><![CDATA[
 <configuration xmlns="http://logging.apache.org/log4php/">
     <renderer renderedClass="Person" renderingClass="PersonRenderer" />
     <appender name="defualt" class="LoggerAppenderEcho" />
     <root>
         <appender_ref ref="defualt" />
     </root>
 </configuration>
 ]]></pre>
 						</div>
 						<div class="tab-pane">
 <pre class="prettyprint linenums"><![CDATA[
 array(
     'renderers' => array(
         array(
             'renderedClass' => 'Person',
             'renderingClass' => 'PersonRenderer'
         )
     ),
     'appenders' => array(
         'default' => array(
             'class' => 'LoggerAppenderEcho',
         ),
     ),
     'rootLogger' => array(
         'appenders' => array('default'),
     ),
 )
 ]]></pre>
 						</div>
 					</div>
 				</div>


 				<p>If the same code is run as above, the following output is produced:</p>

 <pre class="prettyprint linenums"><![CDATA[
 INFO - Here comes the person:
 INFO - John Doe (37)
 ]]></pre>
 				<p>Which is much more readable than the default rendering.</p>
 			</subsection>

 			<subsection name="Overriding the default renderer">
 				<p>It is possible to set your own custom renderer as the default renderer.</p>

 				<p>For example, if you're not happy with the way in which the default renderer converts objects,
 				you can create your own renderer:</p>

 <pre class="prettyprint linenums"><![CDATA[
 class MyRenderer implements LoggerRenderer {
     public function render($input) {
         return var_dump($input);
     }
 }
 ]]></pre>

 				<p>And set it as the default renderer in the configuration:</p>

 				<div class="auto-tabs">
 					<ul>
 						<li>XML</li>
 						<li>PHP</li>
 					</ul>

 					<div class="tab-content">
 						<div class="tab-pane">
 <pre class="prettyprint linenums"><![CDATA[
 <configuration xmlns="http://logging.apache.org/log4php/">
     <defaultRenderer renderingClass="MyRenderer" />
     <appender name="defualt" class="LoggerAppenderEcho" />
     <root>
         <appender_ref ref="defualt" />
     </root>
 </configuration>
 ]]></pre>
 						</div>
 						<div class="tab-pane">
 <pre class="prettyprint linenums"><![CDATA[
 array(
     'defaultRenderer' => 'MyRenderer',
     'appenders' => array(
         'default' => array(
             'class' => 'LoggerAppenderEcho',
         ),
     ),
     'rootLogger' => array(
         'appenders' => array('default'),
     ),
 )
 ]]></pre>
 						</div>
 					</div>
 				</div>

 				<p>Logging a Person object using this configuration will make log4php fall back to the newly
 				defined default renderer, which uses <code>var_dump</code> instead of <code>print_r</code>, and
 				the result will look like:</p>

 <pre class="prettyprint linenums"><![CDATA[
 INFO - Here comes the person:
 class Person#5 (3) {
   public $firstName =>
   string(4) "John"
   public $lastName =>
   string(3) "Doe"
   public $age =>
   int(37)
 }
 ]]></pre>
 			</subsection>

 			<subsection name="Class hierarchy">
 				<p>Object rendering follows the class hierarchy. </p>

 				<p>For example, if there is a class named Fruit, and classes Orange, Lemon and Apple all extend Fruit.
 				When FruitRenderer is registered as renderer for the Fruit class, all subclasses of Fruit will also
 				be rendered by FruitRenderer. Of course, it is possible to override this by registering OrangeRenderer
 				as renderer for the Orange class.</p>
 			</subsection>
 		</section>
 	</body>
 </document>
	<?xml version="1.0" encoding="UTF-8"?>
	<!--
	Licensed to the Apache Software Foundation (ASF) under one or more
	contributor license agreements. See the NOTICE file distributed with
	this work for additional information regarding copyright ownership.
	The ASF licenses this file to You under the Apache License, Version 2.0
	(the "License"); you may not use this file except in compliance with
	the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	-->
	<document xmlns="http://maven.apache.org/XDOC/2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/XDOC/2.0 http://maven.apache.org/xsd/xdoc-2.0.xsd">

	<properties>
	<title>Renderers</title>
	</properties>

	<body>
	<section name="Renderers">
	<p>Apache log4php can log more than just string messages. If you try to log an object it will be converted
	to a string and logged. The component which converts Objects to strings in log4php is called a
	<em>renderer</em>.</p>

	<subsection name="Default renderer">

	<p>For example, let's say that an application uses a Person object, like this one:</p>

	<pre class="prettyprint linenums"><![CDATA[
	class Person {
	public $firstName;
	public $lastName;
	public $age;
	}
	]]></pre>

	<p>If you try logging it:</p>

	<pre class="prettyprint linenums"><![CDATA[
	$person = new Person();
	$person->firstName = 'John';
	$person->lastName = 'Doe';
	$person->age = 37;

	$logger = Logger::getLogger('main');
	$logger->info("Here comes the person:");
	$logger->info($person);
	]]></pre>
	<p>Log4php will render it using the default renderer and you will end the output will look something
	like:</p>

	<pre class="prettyprint linenums"><![CDATA[
	INFO - Here comes the person:
	INFO - Person Object
	(
	[firstName] => John
	[lastName] => Doe
	[age] => 37
	)
	]]></pre>

	</subsection>

	<subsection name="Creating a custom renderer">
	<p>In order to make log4php log the Person object in a more readable format, a custom renderer
	class can be defined which will convert Person objects to a string suitable for logging.</p>

	<p>Let's call this renderer class PersonRenderer.</p>

	<pre class="prettyprint linenums"><![CDATA[
	/** All renderers must implement the LoggerRenderer interface. */
	class PersonRenderer implements LoggerRenderer {
	public function render($person) {
	return "{$person->firstName} {$person->lastName} ({$person->age})";
	}
	}
	]]></pre>

	<p>Now log4php has to be configured to use PersonRenderer for rendering Person objects. This is done
	in the configuration file.</p>

	<div class="auto-tabs">
	<ul>
	<li>XML</li>
	<li>PHP</li>
	</ul>

	<div class="tab-content">
	<div class="tab-pane">
	<pre class="prettyprint linenums"><![CDATA[
	<configuration xmlns="http://logging.apache.org/log4php/">
	<renderer renderedClass="Person" renderingClass="PersonRenderer" />
	<appender name="defualt" class="LoggerAppenderEcho" />
	<root>
	<appender_ref ref="defualt" />
	</root>
	</configuration>
	]]></pre>
	</div>
	<div class="tab-pane">
	<pre class="prettyprint linenums"><![CDATA[
	array(
	'renderers' => array(
	array(
	'renderedClass' => 'Person',
	'renderingClass' => 'PersonRenderer'
	)
	),
	'appenders' => array(
	'default' => array(
	'class' => 'LoggerAppenderEcho',
	),
	),
	'rootLogger' => array(
	'appenders' => array('default'),
	),
	)
	]]></pre>
	</div>
	</div>
	</div>


	<p>If the same code is run as above, the following output is produced:</p>

	<pre class="prettyprint linenums"><![CDATA[
	INFO - Here comes the person:
	INFO - John Doe (37)
	]]></pre>
	<p>Which is much more readable than the default rendering.</p>
	</subsection>

	<subsection name="Overriding the default renderer">
	<p>It is possible to set your own custom renderer as the default renderer.</p>

	<p>For example, if you're not happy with the way in which the default renderer converts objects,
	you can create your own renderer:</p>

	<pre class="prettyprint linenums"><![CDATA[
	class MyRenderer implements LoggerRenderer {
	public function render($input) {
	return var_dump($input);
	}
	}
	]]></pre>

	<p>And set it as the default renderer in the configuration:</p>

	<div class="auto-tabs">
	<ul>
	<li>XML</li>
	<li>PHP</li>
	</ul>

	<div class="tab-content">
	<div class="tab-pane">
	<pre class="prettyprint linenums"><![CDATA[
	<configuration xmlns="http://logging.apache.org/log4php/">
	<defaultRenderer renderingClass="MyRenderer" />
	<appender name="defualt" class="LoggerAppenderEcho" />
	<root>
	<appender_ref ref="defualt" />
	</root>
	</configuration>
	]]></pre>
	</div>
	<div class="tab-pane">
	<pre class="prettyprint linenums"><![CDATA[
	array(
	'defaultRenderer' => 'MyRenderer',
	'appenders' => array(
	'default' => array(
	'class' => 'LoggerAppenderEcho',
	),
	),
	'rootLogger' => array(
	'appenders' => array('default'),
	),
	)
	]]></pre>
	</div>
	</div>
	</div>

	<p>Logging a Person object using this configuration will make log4php fall back to the newly
	defined default renderer, which uses <code>var_dump</code> instead of <code>print_r</code>, and
	the result will look like:</p>

	<pre class="prettyprint linenums"><![CDATA[
	INFO - Here comes the person:
	class Person#5 (3) {
	public $firstName =>
	string(4) "John"
	public $lastName =>
	string(3) "Doe"
	public $age =>
	int(37)
	}
	]]></pre>
	</subsection>

	<subsection name="Class hierarchy">
	<p>Object rendering follows the class hierarchy. </p>

	<p>For example, if there is a class named Fruit, and classes Orange, Lemon and Apple all extend Fruit.
	When FruitRenderer is registered as renderer for the Fruit class, all subclasses of Fruit will also
	be rendered by FruitRenderer. Of course, it is possible to override this by registering OrangeRenderer
	as renderer for the Orange class.</p>
	</subsection>
	</section>
	</body>
	</document>