Java Explorer and ActiveX

Platform requirement

In order to view the demos which use Java Explorer and ActiveX, you'll need to run Internet Explorer on a Windows 95 or NT machine.

The tear program

installDir/java/server/bin_intelnt contains tear.exe which is used by the ActiveX control in order to read data files via a URL.

ActiveX Version Control

If you've already used Frank's DXView ActiveX control on your computer, then it's possible that there will be a version mismatch. CAB files do carry a version number and the system should download a new CAB file if the version number is later than one which is already installed however this mechanism might fail.

On your NT machine, the regsvr32 command can be used to uninstall an existing DXView control. Then pointing your browser at one of these web pages which references DXView will automatically install a new DXView on your computer.

Data Transfer

In the current implementation connecting Java Explorer and ActiveX, Data Explorer is exporting objects in ascii format. The reason for this is that there are some byte swapping issues to be resolved before the data can be exported in binary format. Exporting in ascii format does not affect the rendered image however it does require additional execution time on the server machine, additional bandwidth to transmit an object which is much larger than the binary version, and more processing time on the client machine in order to perform type conversion on the ascii input. In other words, performance should improve over what you experience in these demos.

Security

Active X controls have access to the capabilities and resources of the local host. Java applets on the other hand, run in a sandbox which restricts their access.

Java Explorer applets need to communicate with the DXView ActiveX control. By default, Internet Explorer prevents this from happening so that the Java applets in Java Explorer aren't permitted too much access to the machine. There are two ways to work around this. One is to digitally sign the CAB file which contains the applets and Active X controls. (We'll pursue this.) The other is to count on the browser user to relax the Internet Explorer security restrictions.

Internet Options

Choose 'View/Internet Options' from the menubar. You'll get a dialog box like this:

In this dialog box, switch to the Security page and select Local intranet zone then specify Custom (for expert users). Then click on the Settings button.

Security Settings

Enable everything. Under Java Permissions specify Custom.

This selection will cause the dialog to present a Java Custom Settings button which you then click.

Local Intranet Zone

Enable everything. Click on OK in all three dialog boxes. Now you're good to go.

Web Page Creation

Java Explorer's automatic web page creation facility allows the user to specify a data type for transmission to the client. Now it generates web pages which include ActiveX controls if the data type specified by the user would require such a control.

These Demos

There are just a few demos available which show the ability to connect Java Explorer with ActiveX components. Although they visualize atmospheric and atomic (a.k.a sci-vis) data sets, many other types of visualizations are possible with this mechanism and will be included in the next go around.