The HotJavaTM Browser figures out what application to use to display a file by referencing its MIME (Multipurpose Internet Mail Extensions) type. This tells HotJava the general type of file (text, audio, image, video, application, message, or multipart), and a more specific subtype (e.g. PostScript, TIFF, ZIP compressed data, and so on). The HotJava Browser uses this information, or the file's extension if the MIME type is not available, to determine the application to use to display the file. It does this by looking at a table that maps MIME types and file extensions to viewer actions. This mapping, which you can view or extend using the Edit->Preferences->Viewer Applications page, tells HotJava to do one of the following:

  1. Display the file within the browser (HTML, ASCII text, GIF, and JPEG files)
  2. View the file in another application
  3. Save the file
  4. Ask the user what to do with the file

You must tell the HotJava Browser where on your system to find the external applications (case 2 above) listed in the viewer application mappings. You do this by setting the exec.path property in your HotJava properties file. (The exception is when you add a new content type, with the action View in Application, and you explicitly specify the full path name for the application; in this case you do not have to list that particular application's path in your exec.path property.)

If you try to download a file and the HotJava Browser displays the message Unable to Launch Viewer, you probably do not have your exec.path property set correctly.

The exec.path property is a vertical bar-separated list of full directory names on your machine where the HotJava Browser should look for external viewer applications.

Refer to the section below that corresponds to your platform for information about setting the exec.path property for the supported set of viewer applications.

Windows 95/NT Systems
Solaris Systems

Setting exec.path on Windows 95/NT

On Windows systems, the properties file is in your home directory if the environment variable HOME, HOMEDRIVE, or HOMEPATH is set. Otherwise it is: 
   <hotjava-install-directory>\.hotjava\properties
Add the exec.path setting to this file. Note that you need to quit the HotJava Browser before editing this file, or else your edits will be lost when you later quit the current browser session.

A typical exec.path setting on Windows NT would be: 

   exec.path=c:\\winnt35\\system32|c:\\winnt35

Note the double \\'s in this property. The backslash (\) is the Escape character for the properties file. This means HotJava interprets the character following a \ literally. Whenever HotJava finds a \ in the properties file, it ignores any special meanings for the character that follows it. Since the \ character itself has a special meaning, you must use double backslash (\\) in the properties file to get a single backslash (\).

To ensure that HotJava can execute the default set of applications that the HotJava Browser might launch on Windows 95/NT systems, make sure your exec.path property lists the paths for these applications: wordpad and mplayer.

Setting exec.path on Solaris Systems

On Solaris systems, your properties file is: 
   <your-home-directory>/.hotjava/properties
Add the exec.path setting to this file. Note that you need to quit the HotJava Browser before editing this file, or else your edits will be lost when you later quit the current browser session.

A typical setting of the exec.path property for Solaris users would be: 

   exec.path=/usr/openwin/bin|/usr/local/bin|/bin

To ensure that HotJava can execute the default set of applications that the HotJava Browser might launch on Solaris systems, make sure your exec.path property lists the paths for these applications: imagetool, xterm, troff, nroff, col, more, xdvi, audiotool, and mpeg_play.

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