Mac OS Runtime for Java™ (MRJ) is Apple's implementation of a Java execution environment based on technology from Sun Microsystems, Inc.
The pre-release version comes with three demonstration utilities that use MRJ facilities to run Java applets within a standalone viewer application, within an OpenDoc™ document, and within a screen saver.
In the final release version of MRJ, interfaces to the runtime environment will be provided so that application developers can use MRJ to run Java code within their products.
System Requirements
To use Mac OS Runtime for Java, you need a Power Macintosh, or a 68030 or 68040 Macintosh, running System 7.5 or later. You need approximately 5 megabytes of free disk space, and at least 8 megabytes of memory, though 16 or more megabytes of RAM are recommended. On 680x0 systems, you need to have the CFM-68K Enabler installed. The MRJ installer adds this enabler if you do not already have it.
The standalone application Apple Applet Runner will work with the above configuration.
To use the Apple Applet Viewer for OpenDoc, you need to have OpenDoc 1.0.4 or later installed. It is suggested that you set the OpenDoc default memory to 768K or more to use the pre-release applet viewer with OpenDoc (see the OpenDoc documentation for details on setting the default memory allocation).
To run the Apple Applet Screen Saver module, you will need to use it with After Dark™ from Berkeley Systems, Inc., or with another screen saver that can run After Dark modules.
In order to run applets over the internet, you need to have MacTCP 2.0.4 or later, or OpenTransport 1.1 or later with TCP/IP, and an active Internet connection.
Cyberdog 1.1 and later are compatible with MRJ and the Apple Applet Viewer.
The runtime system software components use roughly 1 megabyte of RAM and 3 megabytes of disk space.
Components of This Release
This release consists of the system components necessary for Java, and three demonstration tools that use these components to run Java applets. In later releases, the API for using the runtime technology will be published so that other application developers can make use of it.
System Components
The MRJ installer puts a folder named "MRJ Libraries" in the Extensions folder of the active System Folder. This folder contains two files necessary for Java support: MRJLib and MRJClasses.
Apple Applet Runner
This is a demonstration application that lets you run Java applets, either from your local disk or over the internet, if you have MacTCP or Open Transport installed, and have an active Internet connection. It does not require OpenDoc.
You can open URLs or local HTML files containing <applet> tags from the File menu. In addition, you can drop HTML files containing <applet> tags onto the Apple Applet Runner application icon from the Finder.
Apple Applet Runner can remember URLs of local or remote applets. Some sample URLs are provided. In addition, some of the demonstration applets from the Sun 1.0.2 Java Development Kit (JDK) for Mac OS are provided in the MRJ folder.
Apple Applet Viewer (for OpenDoc)
This is an OpenDoc viewer that lets you incorporate Java applets into your OpenDoc documents.
Apple Applet Viewer requires OpenDoc 1.0.4 or later in order to run. A folder called "Apple Applet Viewer" is installed in your Editors folder. The Apple Applet Viewer Stationery file is installed in your Stationery folder. The stationery file may then be used with other OpenDoc documents. See your OpenDoc documentation for further information.
If you do not have OpenDoc installed, the editor and stationery files are left in the MRJ folder that the installer created. You can drag these items to the appropriate folders after installing OpenDoc.
You can drag and drop two types of applet specifiers onto an Apple Applet Viewer frame within an OpenDoc document: 1) a text string containing a URL for an html document that contains the applet tag, or 2) a Finder icon for an html file containing an applet tag.
Apple Applet Screen Saver
This is a demonstration screen saver module that can be used with AfterDark™ from Berkeley Systems, Inc. (or another screen saver that supports AfterDark modules) to run applets when the screen saver kicks in. Consult your screen saver documentation for further information about installing the module. It does not require OpenDoc.
Further Information and Reporting Problems
Please connect to our website at:
http://devtools.apple.com/mrj/
to find out about future releases of the Mac OS Runtime for Java, and for information on how to report problems with the software.
Other Applets on the Internet
There are by now thousands of applets available on the Internet. Two starting points for finding applets are:
http://java.sun.com/
and
http://www.gamelan.com/
Known Problems
• With some applets that load large (or many) images or sounds, not all images or sounds may be present. Quitting and relaunching the MRJ runner or viewer, and all other MRJ viewers may free up enough memory so that all the applet's images or sounds may be loaded.
• If you attempt to load an applet from across the Internet, and the network is slow in responding, the network is down, or the URL is incorrect, it may take several minutes for the applet runner or viewer to respond.
• When there is very little free memory available (under 100K or so), the applet viewer may hang when trying to load complex applets. Be careful in low memory situations.
• MRJ requires that CFM-68K be active on 680x0 machines in order to run. The MRJ installer places the CFM-68K Enabler in your Extensions folder, if necessary, and tells you to restart after installing. If you attempt to run MRJ without restarting, or if you remove the enabler or disable it using the Extensions Manager or another mechanism, MRJ viewers will not work, and may crash.
Pre-release Software
This is a pre-release of Mac OS Runtime for Java (MRJ). You should exercise caution when running pre-release software. See the Licensing Agreement (available in the installer) for further details about pre-release software.
Java not Fault-tolerant
The Java technology is not fault-tolerant and is not designed, manufactured or intended for use or resale as on-line control equipment in the operation of nuclear facilities, aircraft navigation or communication systems, or air traffic control machines in which the failure of the Java technology or Mac OS Runtime for Java could lead directly to death, personal injury, or severe physical or environmental damage.
Java Trademark Information
Java and all Java-based trademarks and logos are trademarks or registered trademarks of Sun Microsystems, Inc. in the U.S. and other countries.
