applet guide


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Development notes on using Autoplot as an applet. Recent examples:

Older examples: Showing timing [1]. Other [2] and [3].


  1. Installation
    1. Basic
    2. Testing Clients
    3. Advanced: Pre-load
    4. Advanced: Compressed
    5. Tips
  2. Parameters
  3. Methods
  4. Development Notes

1. Installation

Only a small number of DataSources support the security restrictions of applets. These include: qds, d2s, tsds. The dataSetURL must be to the same URL that the applet was loaded from.

1.1. Basic

<applet width="800" height="400" id="applet1" code="org.virbo.autoplot.AutoplotApplet" archive="AutoplotApplet.jar">
   <param name="dataSetURL" value="">          

1.2. Testing Clients

Right now, only the Sun java plug-in for Mozilla firefox is supported. This can be tested at: We intend to support other clients as well, including the OpenJDK plugin, see bug ticket.

1.3. Advanced: Pre-load

To load the Java Virtual Machine in the background after the page has loaded but before the user has had a chance to initiate an applet visualization, see

1.4. Advanced: Compressed

The applet jar file can be compressed from 3 MB to 0.3 MB using pack200 and proguard (each give about a factor-of-three compression). See most recent applet release at and select the html file named AutoplotAppletCompressed.html. See page source for usage example.

The procedure for building Autoplot and the applet is described in build from source. The pack200 and proguard steps have been added to the build process. A packed applet requires a .htaccess file. See the file named htaccess.txt.

1.5. Tips

  • Change applet memory settings:
  • Clear cache on Linux with rm -rf ~/.java/deployment/cache
  • Clear cache on Windows with Control Panel -> Java -> General Tab -> "Temporary Internet Files Section -> Settings" -> Delete Files
  • Clear cache on Mac using Finder->Applications->Utilities->Java->Java Preferences->Delete Files

2. Parameters

See api#Common for the list of all parameters. Applet parameters are specified as <param name="NAME" value="VALUE">

  • splashImage is the image to use as the preview as the applet initializes.
  • clickCallback is a javascript function to call with click info. <clickCallback>( plotid, xdatum, ydatum, xcanvas, ycanvas, clickType )
  • statusCallback the name of a javascript function to call with status. It should take one string argument, which will describe the status. These include:
    • readParameters the configuration parameters have been read in.
    • dataSourceSet the data source is resolved.
    • dataSourceLoaded the data is loaded.
    • ready the initial work is complete and the applet is waiting for user interaction.
  • timeCallback the name of a javascript function to call to indicate the current x-axis range. This is a string.
  • clickCallback The name of a javascript function which will get the location of clicks. For most recent test version, see the latest release at Autoplot_Change_Log and select AutoplotAppletOnClick.html. See page source for usage example. Initial version: [4].
    • onClick,label=Show Coordinates onClick is a javascript routine name. Show Coordinates is the label in the context menu.
  • contextOverview=on (off is default.) Show two-panels, lower panel is context plot, upper panel is zoom in.

3. Methods

Applet methods can be called from Javascript. For example, if the applet's id is applet_1, then in JavaScript, one can call

applet_1.setTimeRange( '2009-01-01' )

because the applet defines a public method setTimeRange that accepts a string parameter.

  • setTimeRange(String). The string is parsed as a time range and the x axis is set to the new range.
  • setDataSetURL(String). Point the applet to a new data source.
  • setCanvasFont(String). Reset the canvas font. (Broken in current release.)
  • setDomNode( String name, String value ). Uses Java introspection to set the value of the property identified. This uses the object serialization defined in QStream to parse strings into objects. Hopefully any type allowed in the dom tree will work here.

For example:

 setDomNode( 'timeRange', '2009-05-06' )
 setDomNode( 'plots[0].xaxis.log', 'true' )  # TODO: I think the indexed variables don't work presently.
 setDomNode( 'options.drawMinorGrid', 'true' )
  • printDomNode( String name ) Uses Java introspection and QStream's serialize delegates to provide a string representation of the property. You cannot at this time get the string back because of limitations in how we use Javascript and java, but this provides a means of displaying the node in the java console. TODO: fix this limitation
 printDomNode( 'timeRange' )
 printDomNode( 'plots[0].xaxis.log' )

When adding to the applet's API, the thread calling the applet is considered a hostile thread and a security exception will be thrown when a setter is called. Wrap the setter in a Runnable, then pass the Runnable to SwingUtilities.invokeLater so the code is run from a trusted thread.

4. Development Notes


Many of these problems have been fixed. These notes are kept for reference only

Load applet w/o page hang

Note: This is no longer a problem. See

In this example,, jQuery + a JavaScript setTimeout() call is used to make the applet jar files loaded and the JVM is start after the page load is complete (and the user can interact with it normally). Note that the extra step of selecting the "Show Applet" button is needed - otherwise the setTimeRange function is not found. This is a bug in the Applet - see The alternative is to put an alert() right before the call to setTimeRange. Really. We have tried many work-arounds for this, but none allow for the background load + no "Show Applet" button.

The applet does not work in FF 3.07 on WinXP with JRE 1.6.0_07, possibly due to this problem: Works on IE7 and Safari ... A hint: Safari gives

liveconnect: JavaScript: default security policy=

while FF says

liveconnect: JavaScript: default security policy=

Bottom of this thread suggests reverse DNS lookup is needed:

Java console on Mac:

TODO: Try running applet from (which appears in the reverse lookup for or explicitly use ip address instead of

See also:

It appears that we must wait until the applet internally has tried to connect to the server before making a call to the applet with Javascript that requires a request to the server.

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