Some times your extension may need other resources. It can for
for example be an icon, a javascript file, a JSP file or something
else. Fortunately this is very easy. You need to put the extension
in a JAR file. As usual the extension definition XML file should be
at META-INF/extensions.xml. Everything you put in
the JAR file inside the resources/ directory
will automatically be extracted by the extension system to a directory
on the web server. Here is another "Hello world" example which uses a
custom JSP file to display the message. There is also a custom icon.
<extensions xmlns="http://base.thep.lu.se/extensions.xsd">
<extension
id="net.sf.basedb.clients.web.menu.extensions.hellojspworld"
extends="net.sf.basedb.clients.web.menu.extensions"
>
<index>4</index>
<about>
<name>Hello JSP world</name>
<description>
This example uses a custom JSP file to display the
"Hello world" message instead of a javascript popup.
</description>
</about>
<action-factory>
<factory-class>
net.sf.basedb.clients.web.extensions.menu.FixedMenuItemFactory
</factory-class>
<parameters>
<title>Hello JSP world!</title>
<tooltip>Opens a JSP file with the message</tooltip>
<onClick>
Main.openPopup('$HOME$/hello_world.jsp?ID=' + getSessionId(), 'HelloJspWorld', 400, 300)
</onClick>
<icon>~/images/world.png</icon>
</parameters>
</action-factory>
</extension>
</extensions>
The JAR file should have have the following contents:
META-INF/extensions.XML resources/hello_world.jsp resources/images/world.png
When this extension is installed the hello_world.jsp
and world.png files are automatically extracted
to the web servers file system. Each extension is given a unique
HOME directory to make sure that extensions doesn't interfere
with each other. The URL to the home directory is made available in the
$HOME$ variable. All factory settings that have
been annotated with the VariableSetter$HOME$ which is replaced
with the real URL. It is also possible to use the $ROOT$
variable to get the root URL for the BASE web application. Never use
/base/... since users may install BASE into another
path.
The tilde (~) in the <icon> tag value
is also replaced with the HOME path. Note that this kind of
replacement is only done on factory settings that have been annotated
with the PathSetter
![[Note]](../../gfx/admonitions/note.gif) |
Note |
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Unfortunately, the custom JSP file can't use classes that
are located in the extension's JAR file. The reason is that the
JAR file is not known to Tomcat and Tomcat will not look in the
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It is possible for an extension to use a custom javascript or stylesheet.
However, this doesn't happen automatically and may not be enabled
for all extension points. If an extension needs this functionality
the action factory or renderer factory must call
JspContext.addScript() or
JspContext.addStylesheet() from the
prepareContext() method.
The AbstractJspActionFactoryAbstractJspRendererFactory
Factories that are extending one of those two classes can use
<script> and
<stylesheet> tags in the
<parameters> section for an
extensions. Each tag may be used more than one time. The
values are subject to path and variable substitution.
<action-factory>
<factory-class>
... some factory class ...
</factory-class>
<parameters>
<script>~/scripts/custom.js</script>
<stylesheet>~/css/custom.css</stylesheet>
... other parameters ...
</parameters>
</action-factory>
If scripts and stylesheets has been added to the JSP context the extension system will, in most cases, include the proper HTML to link in the requested scripts and/or stylesheet.
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Use UTF-8 character encoding |
|---|---|
The script and stylesheet files should use use UTF-8 character encoding. Otherwise they may not work as expected in BASE. |
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All extension points doesn't support custom scripts/stylesheets |
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In some cases the rendering of the HTML page has gone to far to make is possible to include custom scripts and stylesheets. This is for example the case with the extensions menu. Always check the documentation for the extension point if scripts and stylesheets are supported or not. |
The drawback with a custom JSP file is that it is not possible to
use classes from the extension's JAR file in the JSP code. The reason
is that the JAR file is not known to Tomcat and Tomcat will not look
in the WEB-INF/extensions folder to try to find
classes.
One workaround is to place classes that are needed by the JSP files
in a separate JAR file that is placed in WEB-INF/lib.
The drawback with this is that it requires a restart of Tomcat. It is
also a second step that has to be performed manually by the person
installing the extension and is maybe forgotten when doing an update.
Another workaround is to use an X-JSP file. This is simply a regular
JSP file that has a .xjsp extension instead of .jsp.
The .xjsp extension will trigger the use of a different
compiler that knows how to include the extension's JAR file in the class
path.
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X-JSP is experimental |
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The X-JSP compiler depends on functionality that is internal to Tomcat. The JSP compiler is not part of any open specification and the implementation details may change at any time. This means that the X-JSP compiler may or may not work with future versions of Tomcat. We have currently tested it with Tomcat 6.0.14 only. It will most likely not work with other servlet containers.
Adding support for X-JSP requires that a JAR file with the
X-JSP compiler is installed into Tomcat's internal |