<?xml version="1.0"?>
<!DOCTYPE document [
  <!ENTITY project SYSTEM "project.xml">
]>
<document url="jasper-howto.html">

    &project;

    <properties>
        <author email="glenn@apache.org">Glenn L. Nielsen</author>
        <title>Jasper 2 JSP Engine How To</title>
    </properties>

<body>

<section name="Table of Contents">
<p>
<a href="#Introduction">Introduction</a><br />
<a href="#Configuration">Configuration</a><br />
<a href="#Production Configuration">Production Configuration</a><br />
<a href="#Web Application Compilation">Web Application Compilation</a><br />
<a href="#Using Jikes">Using Jikes</a><br />
</p>
</section>

<section name="Introduction">

<p>Tomcat 5.5 uses the Jasper 2 JSP Engine to implement
the <a href="http://java.sun.com/products/jsp/">JavaServer Pages 2.0</a>
specification.</p>

<p>Jasper 2 has been redesigned to significantly improve performance over
the orignal Jasper.  In addition to general code improvements the following
changes were made:
<ul>
<li><strong>JSP Custom Tag Pooling</strong> - The java objects instantiated
for JSP Custom Tags can now be pooled and reused.  This significantly boosts
the performance of JSP pages which use custom tags.</li>
<li><strong>Background JSP compilation</strong> - If you make a change to
a JSP page which had already been compiled Jasper 2 can recompile that
page in the background.  The previously compiled JSP page will still be
available to serve requests.  Once the new page has been compiled
successfully it will replace the old page.  This helps improve availablity
of your JSP pages on a production server.</li>
<li><strong>Recompile JSP when included page changes</strong> - Jasper 2
can now detect when a page included at compile time from a JSP has changed
and then recompile the parent JSP.</li>
<li><strong>JDT used to compile JSP pages</strong> - The
Eclipse JDT Java compiler is now used to perform JSP java source code
compilation. This compiler loads source dependencies from the container
classloader. Ant and javac can still be used.</li>
</ul>
</p>

<p>Jasper is implemented using the servlet class
<code>org.apache.jasper.servlet.JspServlet</code>.</p>

</section>

<section name="Configuration">

<p>By default Jasper is configured for use when doing web application
development.  See the section <a href="#Production Configuration">
Production Configuration</a> for information on configuring Jasper
for use on a production Tomcat server.</p>

<p>The servlet which implements Jasper is configured using init parameters
in your global <code>$CATALINA_BASE/conf/web.xml</code>.

<ul>
<li><strong>checkInterval</strong> - If development is false and reloading is
true, background compiles are enabled. checkInterval is the time in seconds
between checks to see if a JSP page needs to be recompiled. Default
<code>300</code> seconds.</li>

<li><strong>compiler</strong> - Which compiler Ant should use to compile JSP
pages.  See the Ant documenation for more information. If the value is not set,
then the default Eclipse JDT Java compiler will be used instead of using Ant. 
No default value.</li>

<li><strong>classdebuginfo</strong> - Should the class file be compiled with
debugging information?  <code>true</code> or <code>false</code>, default
<code>true</code>.
</li>

<li><strong>classpath</strong> - What class path should I use while compiling
generated servlets?  By default the classpath is created dynamically based on
the current web application.</li>

<li><strong>development</strong> - Is Jasper used in development mode (will
check for JSP modification on every access)? <code>true</code> or
<code>false</code>, default <code>true</code>.</li>

<li><strong>enablePooling</strong> - Determines whether tag handler pooling is
enabled. <code>true</code> or <code>false</code>, default <code>true</code>.
</li>

<li><strong>ieClassId</strong> - The class-id value to be sent to Internet
Explorer when using &lt;jsp:plugin&gt; tags.   Default
<code>clsid:8AD9C840-044E-11D1-B3E9-00805F499D93</code>.</li>

<li><strong>fork</strong> - Have Ant fork JSP page compiles so they are
performed in a seperate JVM from Tomcat? <code>true</code> or
<code>false</code>, default <code>true</code>.</li>

<li><strong>javaEncoding</strong> - Java file encoding to use for generating
java source files. Default <code>UTF8</code>.</li>

<li><strong>keepgenerated</strong> - Should we keep the generated Java source
code for each page instead of deleting it? <code>true</code> or
<code>false</code>, default <code>true</code>.</li>

<li><strong>mappedfile</strong> - Should we generate static content with one 
print statement per input line, to ease debugging?
<code>true</code> or <code>false</code>, default <code>true</code>.</li>

<li><strong>reloading</strong> - Should Jasper check for modified JSPs?
<code>true</code> or <code>false</code>, default <code>false</code>.</li>

<li><strong>scratchdir</strong> - What scratch directory should we use when
compiling JSP pages? Default is the work directory for the current web
application.</li>

<li><strong>trimSpaces</strong> - Should white spaces in template text between
actions or directives be trimmed ?, default <code>false</code>.</li>
</ul>
</p>

</section>

<section name="Production Configuration">

<p>When using Jasper 2 in a production Tomcat server you should consider
making the following changes from the default configuration.
<ul>
<li><strong>development</strong> - To disable on access checks for JSP
pages compilation set this to <code>false</code>.</li>
<li><strong>fork</strong> - The internal JVM javac compiler used by Ant
has a known memory leak. And Ant requires that java compiles be synchronized,
i.e. only one JSP page can be compiled at a time.  Set fork to
<code>true</code> or do not define it (it is the default value) so that Ant 
compiles JSP pages in a seperate JVM.
This removes the synchronization of JSP page compiles and prevents
all the javac classes from being instantiated and subsequently garbage
collected by the JVM Tomcat is running in. This also works around known 
issues with javac, including memory leaking, as well as JAR file locking
on Windows.</li>
<li><strong>reloading</strong> - To disable background compilation of JSP
pages, which uses one thread per web application, set this to 
<code>false</code>.</li>
</ul>
</p>

</section>

<section name="Web Application Compilation">

<p>Using Ant is the preferred way to compile web applications using JSPC. 
Use the script given below to precompile a webapp:
</p>

<p>
<source>
&lt;project name="Webapp Precompilation" default="all" basedir="."&gt; 

  &lt;target name="jspc"&gt; 

    &lt;taskdef classname="org.apache.jasper.JspC" name="jasper2" &gt; 
      &lt;classpath id="jspc.classpath"&gt; 
        &lt;pathelement location="${java.home}/../lib/tools.jar"/&gt; 
        &lt;fileset dir="${tomcat.home}/bin"&gt; 
          &lt;include name="*.jar"/&gt; 
        &lt;/fileset&gt; 
        &lt;fileset dir="${tomcat.home}/server/lib"&gt; 
          &lt;include name="*.jar"/&gt; 
        &lt;/fileset&gt; 
        &lt;fileset dir="${tomcat.home}/common/lib"&gt; 
          &lt;include name="*.jar"/&gt; 
        &lt;/fileset&gt; 
      &lt;/classpath&gt; 
    &lt;/taskdef&gt; 

    &lt;jasper2 
             validateXml="false" 
             uriroot="${webapp.path}" 
             webXmlFragment="${webapp.path}/WEB-INF/generated_web.xml" 
             outputDir="${webapp.path}/WEB-INF/src" /&gt; 

  &lt;/target&gt; 

  &lt;target name="compile"&gt;

    &lt;mkdir dir="${webapp.path}/WEB-INF/classes"/&gt;
    &lt;mkdir dir="${webapp.path}/WEB-INF/lib"/&gt;

    &lt;javac destdir="${webapp.path}/WEB-INF/classes"
           optimize="off"
           debug="on" failonerror="false"
           srcdir="${webapp.path}/WEB-INF/src" 
	   excludes="**/*.smap"&gt;
      &lt;classpath&gt;
        &lt;pathelement location="${webapp.path}/WEB-INF/classes"/&gt;
        &lt;fileset dir="${webapp.path}/WEB-INF/lib"&gt;
          &lt;include name="*.jar"/&gt;
        &lt;/fileset&gt;
        &lt;pathelement location="${tomcat.home}/common/classes"/&gt;
        &lt;fileset dir="${tomcat.home}/common/lib"&gt;
          &lt;include name="*.jar"/&gt;
        &lt;/fileset&gt;
        &lt;pathelement location="${tomcat.home}/shared/classes"/&gt;
        &lt;fileset dir="${tomcat.home}/shared/lib"&gt;
          &lt;include name="*.jar"/&gt;
        &lt;/fileset&gt;
        &lt;fileset dir="${tomcat.home}/bin"&gt; 
          &lt;include name="*.jar"/&gt; 
        &lt;/fileset&gt; 
      &lt;/classpath&gt;
      &lt;include name="**" /&gt;
      &lt;exclude name="tags/**" /&gt;
    &lt;/javac&gt;

  &lt;/target&gt;

  &lt;target name="all" depends="jspc,compile"&gt;
  &lt;/target&gt;

&lt;/project&gt;
</source>
</p>

<p>
The following command line can be used to run the script
(replacing the tokens with the Tomcat base path and the path to the webapp 
which should be precompiled):<br/>
<source>
$ANT_HOME/bin/ant -Dtomcat.home=&lt;$TOMCAT_HOME&gt; -Dwebapp.path=&lt;$WEBAPP_PATH&gt;
</source>
</p>

<p>
Then, the declarations and mappings for the servlets which were generated 
during the precompilation must be added to the web application deployment
descriptor. Insert the <code>${webapp.path}/WEB-INF/generated_web.xml</code>
at the right place inside the <code>${webapp.path}/WEB-INF/web.xml</code> file.
Restart the web application (using the manager) and test it to verify it is 
running fine with precompiled servlets. An appropriate token placed in the
web application deployment descriptor may also be used to automatically
insert the generated servlet declarations and mappings using Ant filtering 
capabilities. This is actually how all the webapps distributed with Tomcat 
are automatically compiled as part of the build process.
</p>

</section>

<section name="Using Jikes">

<p>If you wish to use
<a href="http://oss.software.ibm.com/developerworks/opensource/jikes/">
Jikes</a> to compile JSP pages:
<ul>
<li>Download and install the Ant JAR in <code>$CATALINA_BASE/common/lib</code>.</li>
<li>Download and install jikes. jikes must support the -encoding option.
Execute <code>jikes -help</code> to verify that it was built with support
for <code>-encoding</code>.</li>
<li>Set the init parameter <code>compiler</code> to <code>jikes</code>.</li>
<li>Define the property <code>-Dbuild.compiler.emacs=true</code> when starting
Tomcat by adding it to your <code>CATALINA_OPTS</code> environment variable.
This changes how jikes outputs error messages so that it is compatible with
Jasper.</li>
<li>If you get an error reporting that jikes can't use UTF8 encoding, try
setting the init parameter <code>javaEncoding</code> to
<code>ISO-8859-1</code>.</li>
</ul>
</p>

</section>
</body>

</document>