Mac OS Runtime for Javaｪ (MRJ) is Appleﾕs implementation of the Java runtime environment based on technology from Sun Microsystems, Inc. MRJ allows Java functionality to be embedded in Mac OS applications. Applications that use this functionality will be able to run Java applets and applications.
MRJ 1.0 implements version 1.0.2 of the Java runtime.
MRJ 1.0 includes Apple Applet Runner, a stand-alone application which allows you to run Java applets, and Apple Applet Viewer, an OpenDoc viewer that allows you to incorporate Java applets into OpenDocｪ documents. The Applets menu in Apple Applet Runner includes a set of applets provided by Sun Microsystems, Inc. These applets were not created by Apple Computer, Inc. and may not follow Apple guidelines for user interaction. For example, buttons in an applet may have different behavior from buttons in applications developed specifically for the Mac OS.
A software development kit (SDK) is available for MRJ. The MRJ SDK includes interfaces to the runtime environment that allow software developers to:
･ Enable a Macintosh application to run Java applets and applications
･ Access the Java runtime from a Macintosh application
･ Call Java methods from C and C++
･ Call native methods from Java
･ Build stand-alone Java applications
The SDK also includes a utility to run Java applications.
See our website at <http://devtools.apple.com/mrj/> to get the MRJ SDK.
System Requirements
This release of Mac OS Runtime for Javaｪ is designed to work on Mac OS-compatible computers with a PowerPC microprocessor. Mac OS Runtime for Java is supported on System 7.5 or later and requires a minimum of 8 MB of RAM (16 MB is strongly recommended) and approximately 7 MB of free disk space. Future versions of MRJ will support System 7.1.1 and later.
The Apple Applet Viewer requires OpenDoc 1.0.4 or later. To get OpenDoc, see the OpenDoc web page at <http://www.opendoc.apple.com/>.
Running applets over the Internet requires MacTCP 2.0.4 or later, or OpenTransport 1.1 or later with TCP/IP, and an active Internet connection.
Cyberdog 2.0 and later will be compatible with MRJ and the Apple Applet Viewer. Cyberdog 2.0 requires OpenDoc 1.1 or later. See the Cyberdog web page at <http://www.cyberdog.apple.com/> for more information.
The MRJ system software components use approximately 3 MB of disk space when installed, and 1 MB of RAM when active (additional RAM is required for Java classes, and for images or sounds used by Java applets or applications).
The Mac OS Runtime for Javaｪ and the Apple Applet Runner do not require OpenDoc.
68K Macintosh Users
This release of Mac OS Runtime for Javaｪ only supports Mac OS-compatible computers with a PowerPC microprocessor. A version which supports the 68K (non PowerPC) Macintosh is nearing completion and will be released in the future. A pre-release version of Mac OS Runtime for Java for 68K can be downloaded from our website <http://devtools.apple.com/mrj/>.
Whatﾕs Installed with MRJ
The MRJ installer places the required software components in your System Folder. The installer does not force you to restart your computer, but you must restart before using MRJ.
Warning: If you have already installed a pre-release version of MRJ, you need to remove the previous version by hand before installing MRJ. Please see the list below for the files to remove from your hard drive. Combining pre-release components of MRJ with the released version can give unpredictable results.
MRJ 1.0 installs:
･ Mac OS Runtime for Javaｪ folder at the root of the startup disk
･ MRJ Libraries folder in the Extensions folder of the active System Folder
･ Text Encoding Converter in the Extensions folder of the active System Folder
･ Text Encodings folder in the active System Folder
If you have OpenDoc installed, MRJ also installs:
･ Apple Applet Viewer Libraries in the Editors folder of the active System Folder
･ Apple Applet Viewer Stationery in the Stationery folder at the root of the startup disk
Running the Apple Applet Runner produces a preferences file named ﾒApple Applet Runner Prefsﾓ in the Preferences folder of the active System Folder. In pre-release version of MRJ, the preferences file was named ﾒApplet Runner Prefsﾓ. If you had a pre-release version of MRJ installed, make sure you throw the ﾒApplet Runner Prefsﾓ file away. (The old file may conflict with preference files created by applet runner applications from other companies.)
Text Encoding Converter and Text Encodings may have been installed on your machine by other software installations. When removing MRJ from your system, make sure you donﾕt remove these files.
Description of MRJ Components
MRJ consists of the system components necessary for Java, and two demonstration tools that use these components to run Java applets.
Note: The MRJ SDK, a separate package (see <http://devtools.apple.com/mrj/> to download the package), comes with tools that let you run Java applications as well. See the MRJ SDK for more information.
System Components
The MRJ installer puts a folder named ﾒMRJ Librariesﾓ in the Extensions folder of the active System Folder. This folder contains two items necessary for Java support: MRJLib and the MRJClasses folder (see ﾒTipsﾓ below to learn how to use this folder to add items to your classpath).
Apple Applet Runner
Apple Applet Runner lets you run Java applets from your local disk. You can also run Java applets over the Internet, provided you have MacTCP or Open Transport installed and have an active Internet connection. Apple Applet Runner 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 remembers URLs of remote (ﾒhttp://ﾉﾓ) or local (ﾒfile:///ﾉﾓ) applets. This information is stored in the ﾒApple Applet Runner Prefsﾓ file in the Preferences folder of the active System Folder. Sample URLs are provided. Demonstration applets from the Sun 1.0.2 Java Development Kit (JDK) for Mac OS are also provided in the MRJ folder.
Apple Applet Viewer (for OpenDoc)
Apple Applet Viewer is an OpenDoc viewer that lets you incorporate Java applets into your OpenDoc documents.
Apple Applet Viewer requires OpenDoc 1.0.4 or later. A folder called ﾒApple Applet Viewerﾓ is installed in your Editors folder and the Apple Applet Viewer Stationery file is installed in your Stationery folder. The stationery file can be used with other OpenDoc documents. Refer to your OpenDoc documentation for additional information.
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.
Further Information and Reporting Problems
Connect to our website at
<http://devtools.apple.com/mrj/>
to find out about future releases of the Mac OS Runtime for Java or get information on how to report problems with the software.
Other Applets on the Internet
There are thousands of applets available on the Internet. Two good starting points for finding applets are:
<http://www.javasoft.com/>
and
<http://www.gamelan.com/>
Tips for Using MRJ
OpenDoc
If you do not have OpenDoc installed at the time you install MRJ, the editor and stationery files will not be installed. If you later install OpenDoc, you must reinstall MRJ to use the editor and stationery files.
Extending the Classpath
Some applets may need access to classes that are not in the same directory as the applet tag. To allow additional Java classes or zip files to be referenced by MRJ when running an applet, do one of two things:
ﾐ Add a codebase parameter to the applet tag. This technique can be used when the classes
are either on your disk or on the Internet. Add a parameter of the form
ﾒcodebase=file:///mydisk/myfolder/myzip.zipﾓ (for classes on your disk) or
ﾒcodebase=http://hostname/dirname/theirzip.zipﾓ (for classes on the Internet)
to the applet tag that is in the .html file you open with Apple Applet Runner or
Apple Applet Viewer. See general Java and html references for more details on
the applet tag format and the codebase parameter.
ﾐ Add an alias to the MRJClasses folder. This technique is useful when you have a
local copy of a .zip file, or a folder with a collection of Java classes, on your disk.
If the item you wish to add is a .zip file or a collection of .class files, you can add
the aliases directly. Put an alias to the item (.zip file or folder) into the MRJ Classes
folder in the Extensions folder in the active System Folder. To add a single class
file to the classpath, make an alias to the folder containing the class file and
put that alias into the MRJ Classes folder.
Note: Currently, any MRJ runners or viewers that are open will have to be quit and relaunched for the new classes to be recognized.
Memory Usage
MRJ uses System memory when running. Applications allocate their own application memory when launched, leaving less memory available to the System, so if you have allocated a large partition to the Apple Applet Runner, Cyberdog, or another application that utilizes MRJ you may have trouble running large Java applets or applications. If you encounter problems running large applets or applications, try quitting any unneeded applications that are running. If you still cannot run the applet or application, use the ﾒGet Infoﾓ window for your application to choose a smaller number in the Preferred Size field for Memory Requirements. Do not set the Preferred Size smaller than the Minimum Size shown for that application.
Known Problems
･ MRJ installs the Text Encoding Converter in your Extensions folder in order to run. To enable the Text Encoding Converter, you must restart your computer before using MRJ. If you attempt to run MRJ without restarting, or if you remove the enabler or disable the extension using the Extensions Manager or another mechanism, MRJ may behave in unexpected ways.
･ Do not remove the Text Encodings folder from the System Folder. Text Encodings are needed for text support in MRJ. Removing this folder may result in incorrect behavior when running MRJ.
･ There is a known problem with the PPCExceptionEnabler extension. This extension is installed by Macintosh Common Lisp (MCL) 3.9. If you have this extension, you must remove it before running MRJ. Future versions of MCL will not require this extension.
･ There are known problems with some applets when using MRJ with Microsoft Internet Explorer, including display problems, sound problems and possible crashes. We are working with Microsoft to resolve these problems in a future release of Internet Explorer.
･ If you are running applications or applets compiled with the JavaSoft 1.0.2 JDK release for Macintosh, you may encounter numerics-related problems. Specifically, floating-point constants (and in some cases computed integer constants) may not be accurate. Any Java virtual machine will encounter these same problems, but we believe these cases to be rare. If possible, use another Java compiler to recompile any applications or applets displaying this problem.
･ With some applets that load large (or many) images or sounds, there may not be enough RAM free to load all the images and sounds. You may be able to free up enough RAM by quitting all applications (such as the Apple Applet Runner and Apple Applet Viewer) that use MRJ. If necessary, try quitting other applications as well. After quitting the applications, try relaunching Apple Applet Runner or Apple Applet Viewer.
･ Some Java applets (such as Clock) or applications that are processor intensive may not give up time to other applets, resulting in other applets opening slowly, running slowly, or failing to open or run. To improve performance, try closing applets or applications that you are not using.
･ The OpenDoc-based Apple Applet Viewer does not have a mechanism to report some types of failures. If an applet does not load in Apple Applet Viewer, try the applet under Apple Applet Runner to see if an error message was generated.
･ This release of MRJ supports System 7.5 and later. A release with support for System 7.1.1 and later, which will also include support for 68K-based Macintoshes, is under development. Please check the website at <http://devtools.apple.com/mrj/> for the latest information, and for beta versions of future releases.
･ In Apple Applet Runner, the Applet menu should not be used while the Properties dialog is on the screen. Using the Applet menu while the Properties dialog is open may crash Apple Applet Runner.
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.
ｩ 1996-1997 Apple Computer. Inc. All rights reserved.
Apple, the Apple logo, LaserWriter, MacTCP, Power Macintosh, Mac, and Macintosh are trademarks of Apple Computer, Inc., registered in the U.S. and other countries. PowerPC is a trademark of International Business Machines Corporation, used under license therefrom. Java and all Java-based trademarks and logos are trademarks or registered trademarks of Sun Microsystems, Inc. in the U.S. and other countries. All other product names are trademarks or registered trademarks of their respective holders. Mention of non-Apple products is for information purposes and constitutes neither an endorsement nor a recommendation. Apple assumes no responsibility with regard to the selection, performance, or use of these products.
