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Cosmetic changes, and correct copyright dates. Add simple overview

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with pointer to the real documentation, and a package.html for the
o.a.c.l.impl package.  Bring various documentation points up to date
with the actual current functionality.


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/logging/trunk@138961 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Craig R. McClanahan
2003-03-30 23:42:36 +00:00
parent e462bae3af
commit 27559f2f8c
16 changed files with 119 additions and 94 deletions
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61
src/java/org/apache/commons/logging/package.html
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@@ -1,6 +1,7 @@
<body>
<p>Simple wrapper API around multiple logging APIs.</p>
<h3>Overview</h3>
<p>This package provides an API for logging in server-based applications that
@@ -14,14 +15,14 @@ prebuilt support for the following:</p>
JDK Logging API</a>, included in JDK 1.4 or later systems. Each named
<a href="Log.html">Log</a> instance is connected to a corresponding
<code>java.util.logging.Logger</code> instance.</li>
<li><a href="http://jakarta.apache.org/avalon/">LogKit</a> from Apache's
Jakarta project. Each named <a href="Log.html">Log</a> instance is
<li><a href="http://avalong.apache.org/logkit/">LogKit</a> from Apache's
Avalon project. Each named <a href="Log.html">Log</a> instance is
connected to a corresponding LogKit <code>Logger</code>.</li>
<li><a href="impl/NoOpLog.html">NoOpLog</a> implementation that simply swallows
all log output, for all named <a href="Log.html">Log</a> isntances.</li>
<li><a href="impl/SimpleLog.html">SimpleLog</a> implementation that writes all
log output, for all named <a href="Log.html">Log</a> instances, to
System.out.</li>
System.err.</li>
</ul>
@@ -37,7 +38,7 @@ convention) after the calling class:
public class Foo {
Log log = LogFactory.getLog(this.class);
static Log log = LogFactory.getLog(this.class);
public void foo() {
...
@@ -53,9 +54,10 @@ convention) after the calling class:
}
</pre>
<p>Unless you configure things differently, all log output will be thrown
away. Therefore, you really will want to review the remainder of this page
in order to understand how to configure logging for your application.</p>
<p>Unless you configure things differently, all log output will be written
to System.err. Therefore, you really will want to review the remainder of
this page in order to understand how to configure logging for your
application.</p>
<h3>Configuring the Commons Logging Package</h3>
@@ -65,11 +67,11 @@ in order to understand how to configure logging for your application.</p>
<p>From an application perspective, the first requirement is to retrieve an
object reference to the <code>LogFactory</code> instance that will be used
to create <code><a href="Log.html">Log</a></code> instances for this application.
This is normally accomplished by calling the static <code>getFactory()</code>
method. This method implements the following discovery algorithm to select
the name of the <code>LogFactory</code> implementation class this application
wants to use:</p>
to create <code><a href="Log.html">Log</a></code> instances for this
application. This is normally accomplished by calling the static
<code>getFactory()</code> method. This method implements the following
discovery algorithm to select the name of the <code>LogFactory</code>
implementation class this application wants to use:</p>
<ul>
<li>Check for a system property named
<code>org.apache.commons.logging.LogFactory</code>.</li>
@@ -98,7 +100,7 @@ otherwise. This allows a copy of <code>commons-logging.jar</code> to be
shared in a multiple class loader environment (such as a servlet container),
but still allow each web application to provide its own <code>LogFactory</code>
implementation, if it so desires. An instance of this class will then be
created, and
created, and cached per class loader.
<h4>The Default <code>LogFactory</code> Implementation</h4>
@@ -119,12 +121,14 @@ implementation uses the following rules:</p>
<code>LogFactory</code> implementation uses the following discovery
process is used:
<ul>
<li>Look for a configuration attribute of this factory named
<code>org.apache.commons.logging.Log</code> (for backwards
compatibility to pre-1.0 versions of this API, an attribute
<code>org.apache.commons.logging.log is also consulted)..</li>
<li>Look for a system property named
<code>org.apache.commons.logging.Log</code> (for backwards
compatibility to pre-1.0 versions of this API, a system property
<code>org.apache.commons.logging.log</code> is also consulted).</li>
<li>Look for a configuration attribute of this factory named
<code>org.apache.commons.logging.Log</code>.</li>
<li>If the Log4J logging system is available in the application
class path, use the corresponding wrapper class
(<a href="impl/Log4JLogger.html">Log4JLogger</a>).</li>
@@ -142,20 +146,8 @@ implementation uses the following rules:</p>
argument to its constructor.</li>
</ul>
<p>If you wish to receive logging output to <code>System.out</code>, but have
not installed one of the three supported logging packages, a simple
<code>Log</code> implementation named <a href="impl/SimpleLog.html">
SimpleLog</a> is available. You can select it, based on the above rules,
by including a system property definition on the command line that starts
your application:</p>
<pre>
java \
-Dorg.apache.commons.logging.Log=org.apache.commons.logging.impl.SimpleLog \
MyApplication
</pre>
<p>See the <a href="impl/SimpleLog.html">SimpleLog</a> JavaDocs for detailed
configuration information for this implementation.</p>
configuration information for this default implementation.</p>
<h4>Configuring the Underlying Logging System</h4>
@@ -192,6 +184,16 @@ component, consists of the following steps:</p>
<code>warn()</code>, <code>error</code>, and <code>fatal()</code>).</li>
</ol>
<p>For convenience, <code>LogFactory</code> also offers a static method
<code>getLog()</code> that combines the typical two-step pattern:</p>
<pre>
Log log = LogFactory.getFactory().getInstance("Foo");
</pre>
<p>into a single method call:</p>
<pre>
Log log = LogFactory.getLog("Foo");
</pre>
<p>For example, you might use the following technique to initialize and
use a <a href="Log.html">Log</a> instance in an application component:</p>
<pre>
@@ -200,7 +202,8 @@ import org.apache.commons.logging.LogFactory;
public class MyComponent {
protected Log log = LogFactory.getLog("my.component");
protected static Log log =
LogFactory.getLog("my.component");
// Called once at startup time
public void start() {