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Java Web Start Resource Loading Tutorial Continued


In this tutorial I create a real-world example app that drills for resources (e.g. properties, icons, images, xml documents, xsl stylesheets, etc.) in the app's jar using Rachel's high-level resource manager getIcon, getImage, getText, getProperties power getter methods hiding the low-level, close-to-the-metal getResource and getResourceAsStream class loader wizardy.

First Impression - ResMan Portrait Anno 2002

Here is a first impression of the ResMan resource loading example app.

ResMan example app portrait

Behind the scene ResMan retrieves from its jar and builds the help menu on-the-fly; runs the overview.xml xml document through an xslt engine using the doc2html.xls stylesheet to show off the resulting hmtl page in the built-in browser as seen above; retrieves Vanessa's portrait vanessa.jpg and hangs it up in tabbed panel; and retrieves Strunk's Style Rule Five marked-up in HTML in strunk.html in a single stroke and much more.

ResMan's Power Getters Unveiled

Retrieving resources from jars is easy if you use Rachel's ResMan's power getters such as ResMan.getText , ResMan.getIcon , ResMan.getImage , ResMan.getXmlDocument , ResMan.getProperties , or ResMan.getInputStream .

Before you can drill for bits you need to tell Rachel all jars holding your treasures (that is, resources such as images, properties, xsl stylesheets, etc.). In the ResMan example all resources reside in the same jar along-side the app's binary byte-code classes.

Example: resman.jar table of contents

CmdShowDocumentBuiltIn.class     demo/common/html/
CmdShowDocumentHousehold.class   demo/common/html/
WebBrowser$1.class               demo/common/html/
WebBrowser.class                 demo/common/html/
ImagePanel.class                 demo/common/image/
XmlTreeModel.class               demo/common/tree/
XmlTreeNodeRenderer.class        demo/common/tree/
AppFrame$1.class                 demo/resman/
AppFrame.class                   demo/resman/
Tool.class                       demo/resman/
inform.gif                       images/
vanessa.jpg                      images/
world2.gif                       images/
MANIFEST.MF                      META-INF/

The rachel.loader.ClassResourceLoader class allows you to identify a jar using a single class (usually dubbed resouche anchor) and spares you from combing your user's Web Start cache to find out the jar's mangled filename. Instead of creating a pure, single-purpose, dummy resource anchor class, abuse the example's demo.resman.Tool class holding the main method and pass it on to ClassResourceLoader. Kick off your bit drilling extravaganza with the one-line magic spell below.

ResMan.setResourceLoader( new ClassResourceLoader( Tool.class ) );

Icons. Use ResMan.getIcon() to get icons from your app's jars. Example:

ImageIcon appIcon = ResMan.getIcon( "images/inform.gif" ); 

Compare this to the low-level, multi-line, heavy-lifting class loader workout below. Use ResMan's power getters and kiss the ClassLoader goodbye.

ClassLoader cl = Tool.class.getClassLoader();
URL appIconUrl = cl.getResource( "images/inform.gif" );
ImageIcon appIcon = new ImageIcon( appIconUrl );

Images. Use the ResMan.getImage one-liner below to get images (aka graphic pictures) from your app's jars. Example:

BufferedImage vanessaImg = ResMan.getImage( "images/vanessa.jpg" );

Rachel uses Java's 1.4 new plugable image i/o toolkit. Out-of-the-box it can read gif, jpeg and png graphics formats. If you need other formats such as bmp or tiff, for example, ship a image i/o plug-in with your app.

Text. Use the ResMan.getText power getter below to get a text file's content stored in your app's jars packed up in a string. Example:

String strunkHtmlSnippet = ResMan.getText( "strunk.html" );

Properties. Use ResMan.getProperties to get a property file stored in your app's jars delivered in a java.util.Properties table to your doorstep. Example:

Properties props = ResMan.getProperties( "" );

Xml Documents. Use ResMan.getXmlDocument to get an xml document stored in your app's jar pre-parsed and stored in a JDOM tree ready-to-use. Example:

Document doc = ResMan.getXmlDocument( "overview.xml" );

Input Streams. If ResMan doesn't sport a power getter for your desired format yet (e.g. mp3 audio, mpeg video, etc.) or if you want to pass on the raw InputStream use ResMan.getInputStream. Example:

InputStream inStream   = ResMan.getInputStream( "overview.xml" );
InputStream xslStream  = ResMan.getInputStream( "doc2html.xsl" );

That's it. That's all there is to it.

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