David Wallace Croft
Java Developers: Abstract: I propose that the implementation of inter-session class caching mechanisms in Java applications and browsers is the technical solution to the current raging debate concerning Java standardization and monopolization. Efficiencies would be improved in both the developer market and in the consumption of computer resources. Microsoft has recently made its position clear with regard to Java 1.1 and 1.2 support: it will not support the core components of RMI, JNI, and, most important to my mind, the JFC. This is somewhat understandable as Microsoft is fighting to preserve its monopoly; truly portable run-time code makes the choice of the operating system somewhat irrelevant. http://www.javaworld.com/jw-10-1997/jw-10-javalobby.html Looking farther down the road, we as developers have to be concerned about the prospect of an effective monopoly from Sun. The number of standard (core) Java packages and classes required of a compliant Java implementation increased from 8 and 211 in Java 1.0 to 23 and 503 in Java 1.1, respectively. If we see another doubling of those numbers with the release of Java 1.2, one has to wonder if Sun isn't simply creating its own virtual monopoly by continuously adding new components to the core Java specification which other companies must struggle to implement, continuously lagging behind Sun's self-awarded head start. In my mind, the most significant advantage of the Java programming language, the feature that makes it a revolutionary leap above and beyond all other programming languages to date, is its guaranteed cross-platform run-time portability. Having a sufficiently rich set of classes as standard available components is vital to the wide-spread acceptance of any portable language. Whereas I applaud Sun's apparent movement toward including specifications in the Java core for a vast number of APIs including what would normally be considered operating system functionality, I have to wonder what risks we as developers are taking by allowing the Java language to become too bloated. At some point it has to stop. One always has the option of using non-core classes in any Java application or applet. The Java language does not restrict the use of the IFC or the AFC simply because the JFC has become standardized. However, having any particular set of classes pre-installed on the client is such a significant performance improvement, in terms of class downloading time and access to trusted native code optimizations, it is clear that one standard will come to dominate. My vote is for the cross-platform, cross-vendor solutions of which I believe the JFC will be. What do we do, however, when several competitors are offering cross-platform, cross-vendor specifications? If we simply wait until Sun incorporates a variant of one of the specifications into its core, we as developers will be punishing future innovators in the market. Whereas we might rely on the goodwill and generosity of Sun to work with competing vendors of superior technologies to integrate the APIs into future versions of Java, we know that the small vendors will lose their time-to-market advantage in the process. What we need is a technical fix. I propose that we rewrite our class loader implementations in our browsers and our Java applications to cache Java classes between sessions. Infrequently used classes would be automatically purged from local storage over time given the algorithms and user-selected choices to constrain long-term storage consumption while meeting class downloading time requirements. Native code optimizations, once accepted given a deliberate acknowledgment of trust by the receiver, would remain resident over multiple sessions until expired through lack of use. End users would have the option to select which classes to permanently maintain, which would normally but not necessarily include a significant number of the core Java classes, and which would be expired over time according to some heuristic. End users would keep the ability, as an option, to always expire classes at the termination of an application or session as is done now for non-pre-installed classes. The new inherent class versioning feature of Java 1.1 could be used to ensure that cached classes are updated as needed between sessions or possibly even within a session at the launch of a new class loader. Microsoft sparked this current conflict with the decision to remove hundreds of Java applets from its web pages citing the bandwidth consumption and delays. Regardless of their true motivations in this action, I find that there is a significant element of truth to this statement. I myself am tempted to pull an applet off of my own home page after seeing the same classes downloaded every single time I open my browser. Over time, the delay adds up to a costly expenditure in terms of both man-hours and bandwidth. Caching downloaded classes between sessions would solve this problem. Indeed, this leaves the door open to a superior class library gaining a de facto advantage over established or standardized class libraries supported by one or some of the early players: older, inferior class libraries will make fewer and fewer cache hits over the Internet, requiring the expenditure of bandwidth and time. Caching classes between sessions promotes competitiveness, rewards innovation and efficiency, and returns freedom of choice to the developers. As it now stands, even if a cross-platform, cross-vendor class that consumes 1/10 of the resources in byte size and execution time is available, there is a strong force against using other than the established, pre-installed Java classes. One might consider that the law of increasing returns would play out in this proposed scenario as well, simply replacing favoritism of those class libraries with the best marketing and largest pre-installed base with those class libraries with the best marketing and largest cached base. This is not true, however, as those applications and applets with loyal repeat customers, such as for in-house applications and popular innovative applets, will have in effect created a niche market where the use of their class libraries can survive until they can pass the threshold required to be recognized and accepted as a superior product by the mass market. As an example of this, consider a Java game engine class library. Rather than relying on the pre-installaton of classes through the expensive and limited distribution of a CD-ROM, game developers can deliver hundreds of kilobytes of class and data files to the players over the Internet once, and only once, with the reliance upon the user's efficient caching class loader. Necessary class version updates would still take place and the end user, not the distributor of a CD-ROM, would then have the option of deciding just how much long-term storage he wanted to dedicate to game given his preferences for minimizing download time, reliance on optimizing smart caching mechanisms, and frequency of play. On the advice of the game provider, the player might even opt to increase cache storage or mark the downloaded classes in the library as immune from purges for a fixed duration. Continuing this example, which is applicable to the vast number of Java development industries, successful game engines would have an advantage due to the increased probability of successful cache hits. This promotes licensing opportunities to game engine developers separate and apart from the game content developers. The layerization of an industry, just as it is in software engineering, promotes efficiency, reliability, and increased application opportunities. One might even imagine that a popular public domain game engine, seeded by the downloads from academic universities over time, might be adopted by a number of for-profit game developers due to its established customer base. These same industries might even find that there is less disincentive to collaborate on a standard set of class libraries now that the monopolistic advantage of pre-installing class libraries has been removed. To summarize, the use of efficient inter-session Java class caching mechanisms would improve resource consumption efficiency, return choice to developers, and make this whole Java language standardization and monopolization debate moot. David Wallace Croft, firstname.lastname@example.org http://www.alumni.caltech.edu/~croft/research/java/cache/
Java Developers: I suggest that it would serve our best interests if major browsers would cache JAR files between sessions. Earlier I had suggested that Java classes should be cached between sessions to prevent stifling developer innovation. As it currently stands, the makers of a particular browser can pre-install a proprietary Java class library on the client and gain a significant advantage over distributors of classes which must be downloaded with each new session. http://www.alumni.caltech.edu/~croft/research/java/cache/ After reading the e-mail discussions on this topic, I see that there are technical issues to be resolved with regard to security, namespace conflicts, and version control. While I am certain that these problems can be worked out for the distribution of individual class files if there is a will, I have recently come to the conclusion that the intersession caching of JAR files may make resolving these issues trivial. By quickly comparing just the hash digests of a requested JAR file to a cached JAR file, a download can be avoided while being reasonably assured that any security, namespace, or version problems are highly improbable. So long as a hash digest can be recomputed and validated the first time a JAR file is downloaded and cached, it should be quite safe to download a large foundation class library from any random server and use it as called by applets from another server, trusted or untrusted. If that hypothetical JAR file were identically copied on a multitude of servers, only the first web server encountered delivering an HTML page with an applet tag requiring that specific archive would actually have to deliver it to the client browser. From then on, it would not need to be downloaded as it would already be cached. To sum it up, if the JAR hash digests match, use the cache. David Wallace Croft Mountaineer Java Users Group (MtJUG) Moderator
David Macias, Group Marketing Manager, Sun: We talked briefly immediately after the online Java gaming session Friday at the JavaOne conference. I had wanted to bring to your attention how crucial it is to the online Java gaming industry for JavaSoft to provide "persistent JAR caching" in Java 1.3 or earlier. As you requested, I am e-mailing you with some information that you may use to study this opportunity. In a nutshell, persistent JAR caching is the ability to cache Java bytecode class files on the client disk drive in the same manner that your web browser caches graphics images and web pages. This is crucial for "thin pipe" clients such as applet users coming in over a modem or even mobile computers. As it currently stands, by requiring a download over a slow modem of all of the Java resources every time an applet is loaded on a daily basis, online Java gaming development as well as other applet applications are severely hindered. Bytecode class file caching could have a significant impact on the acceptance of Java especially if it is introduced in the JDK. With Netscape introducing their new Open API for replacing the virtual machine in their browser with one from JavaSoft, end-users would suddenly see a dramatic improvement in loading applets by simply making the virtual machine switch to a JDK with persistent JAR caching. This would make Java far more palatable to many browser users. To be clear here, persistent JAR caching makes the distribution problem go away. An end-user can download a Java 3D interactive applet game for a few hours the first time the program is run but have it load instantly every day in the future. The bytecode class files will be updated in the cache only as needed, eliminating any need for a pre-install or update of standard Java extensions or third-party libraries for performance. For more extensive arguments regarding this technology with regard to driving this industry, see http://www.alumni.caltech.edu/~croft/research/java/cache/ -- David Wallace Croft, Senior Intelligent Systems Engineer
David Wallace Croft, email@example.com
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