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| <title>5.7. Logging</title><link rel="stylesheet" href="css/stylesheet.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.75.0"><link rel="home" href="index.html" title="Apache Click"><link rel="up" href="ch05.html" title="Chapter 5. Best Practices"><link rel="prev" href="ch05s06.html" title="5.6. Menus"><link rel="next" href="ch05s08.html" title="5.8. Error Handling"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">5.7. Logging</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch05s06.html">Prev</a> </td><th width="60%" align="center">Chapter 5. Best Practices</th><td width="20%" align="right"> <a accesskey="n" href="ch05s08.html">Next</a></td></tr></table><hr></div><div class="sect1" title="5.7. Logging"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="logging"></a>5.7. Logging</h2></div></div></div><p> |
| For application logging you should use one of the well established |
| logging libraries such as Java Util Logging (JUL) or Log4J. |
| </p><p> |
| The library you use will largely depend upon the application server you are targeting. |
| For Apache Tomcat or RedHat JBoss the |
| <a xmlns:fo="http://www.w3.org/1999/XSL/Format" class="external" href="http://logging.apache.org/log4j/" target="_blank">Log4j</a> library is a good |
| choice. While for the IBM WebSphere or Oracle WebLogic application servers Java Util |
| Logging is better choice as this library is better supported. |
| </p><p> |
| If you have to target multiple application servers you should consider using the |
| <a xmlns:fo="http://www.w3.org/1999/XSL/Format" class="external" href="http://www.slf4j.org/" target="_blank">SLF4J</a> library which uses compile time bindings |
| to an underlying logging implementation. |
| </p><p> |
| As a general principle you should |
| probably avoid <a xmlns:fo="http://www.w3.org/1999/XSL/Format" class="external" href="http://jakarta.apache.org/commons/logging/" target="_blank">Commons Logging</a> |
| because of the class loading issues associated with it. If you are using |
| Commons Logging please make sure you have the latest version. |
| </p><p> |
| It is a best place to define a logger method in a common base page, for example: |
| </p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">class</span> BasePage <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">extends</span> Page { |
| |
| <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">protected</span> Logger logger; |
| |
| <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> Logger getLogger() { |
| <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">if</span> (logger == null) { |
| logger = Logger.getLogger(getClass()); |
| } |
| <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">return</span> logger; |
| } |
| }</pre><p>Using this pattern all your application bases should extend |
| <code class="classname">BasePage</code> so they can use the |
| <code class="methodname">getLogger()</code> method. |
| </p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">class</span> CustomerListPage <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">extends</span> BasePage { |
| |
| <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">void</span> onGet() { |
| <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">try</span> { |
| .. |
| } <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">catch</span> (Exception e) { |
| getLogger().error(e); |
| } |
| } |
| }</pre><p>If you have some very heavy debug statement you should possibly use an |
| <code class="methodname">isDebugEnabled</code> switch so it is not invoked if debug is |
| not required. |
| </p><pre class="programlisting"><span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">class</span> CustomerListPage <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">extends</span> BasePage { |
| |
| <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">public</span> <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">void</span> onGet() { |
| <span xmlns:fo="http://www.w3.org/1999/XSL/Format" class="kwd">if</span> (getLogger().isDebugEnabled()) { |
| String msg = .. |
| |
| getLogger().debug(msg); |
| } |
| |
| .. |
| } |
| }</pre><p> |
| Please note the Click logging facility is not designed for application use, |
| and is for Click internal use only. When Click is running in |
| <code class="literal">production</code> mode it will not produce any logging output. |
| By default Click logs to the console using |
| <a xmlns:fo="http://www.w3.org/1999/XSL/Format" class="external" href="../../click-api/org/apache/click/service/ConsoleLogService.html" target="_blank">ConsoleLogService</a>. |
| </p><p> |
| If you need to configure Click to log to an alternative destination please configure a LogService such as |
| <a xmlns:fo="http://www.w3.org/1999/XSL/Format" class="external" href="../../extras-api/org/apache/click/extras/service/JdkLogService.html" target="_blank">JdkLogService</a>, |
| <a xmlns:fo="http://www.w3.org/1999/XSL/Format" class="external" href="../../extras-api/org/apache/click/extras/service/Log4JLogService.html" target="_blank">Log4JLogService</a> or |
| <a xmlns:fo="http://www.w3.org/1999/XSL/Format" class="external" href="../../extras-api/org/apache/click/extras/service/Slf4jLogService.html" target="_blank">Slf4jLogService</a>. |
| </p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ch05s06.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch05.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ch05s08.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">5.6. Menus </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 5.8. Error Handling</td></tr></table></div></body></html> |
