菜单
  

    The Java approach is to prevent these problems from occurring, via the sandbox. The Java interpreter that lives on your local Web browser examines the applet for any untoward instructions as the applet is being loaded. In particular, the applet cannot write files to disk or erase files (one of the mainstays of viruses). Applets are generally considered to be safe, and since this is essential for reliable client/server systems, any bugs in the Java language that allow viruses are rapidly repaired. (It’s worth noting that the browser software actually enforces these security restrictions, and some browsers allow you to select different security levels to provide varying degrees of access to your system.) You might be skeptical of this rather draconian restriction against writing files to your local disk. For example, you may want to build a local database or save data for later use offline. The initial vision seemed to be that eventually everyone would get online to do anything important, but that was soon seen to be impractical (although low-cost “Internet appliances” might someday satisfy the needs of a significant segment of users). The solution is the “signed applet” that uses public-key encryption to verify that an applet does indeed come from where it claims it does. A signed applet can still trash your disk, but the theory is that since you can now hold the applet creator accountable they won’t do vicious things. Java provides a framework for digital signatures so that you will eventually be able to allow an applet to step outside the sandbox if necessary. Digital signatures have missed an important issue, which is the speed that people move around on the Internet. If you download a buggy program and it does something untoward, how long will it be before you discover the damage? It could be days or even weeks. By then, how will you track down the program that’s done it? And what good will it do you at that point?
    7.Internet vs. intranet
    The Web is the most general solution to the client/server problem, so it makes sense that you can use the same technology to solve a subset of the problem, in particular the classic client/server problem within a company. With traditional client/server approaches you have the problem of multiple types of client computers, as well as the difficulty of installing new client software, both of which are handily solved with Web browsers and client-side programming. When Web technology is used for an information network that is restricted to a particular company, it is referred to as an intranet. Intranets provide much greater security than the Internet, since you can physically control access to the servers within your company. In terms of training, it seems that once people understand the general concept of a browser it’s much easier for them to deal with differences in the way pages and applets look, so the learning curve for new kinds of systems seems to be reduced.
    The security problem brings us to one of the pisions that seems to be automatically forming in the world of client-side programming. If your program is running on the Internet, you don’t know what platform it will be working under, and you want to be extra careful that you don’t disseminate buggy code. You need something cross-platform and secure, like a scripting language or Java. 
    If you’re running on an intranet, you might have a different set of constraints. It’s not uncommon that your machines could all be Intel/Windows platforms. On an intranet, you’re responsible for the quality of your own code and can repair bugs when they’re discovered. In addition, you might already have a body of legacy code that you’ve been using in a more traditional client/server approach, whereby you must physically install client programs every time you do an upgrade. The time wasted in installing upgrades is the most compelling reason to move to browsers, because upgrades are invisible and automatic. If you are involved in such an intranet, the most sensible approach to take is the shortest path that allows you to use your existing code base, rather than trying to recode your programs in a new language.
  1. 上一篇:情感分析观点挖掘英文文献和中文翻译
  2. 下一篇:ASP.NET技术英文文献及中文翻译
  1. JSP英文文献和中文翻译

  2. Java技术的Web应用设计模型...

  3. 绿色建筑与室内空气质量英文献和中文翻译

  4. 内河运输船舶碰撞与搁浅...

  5. 产业集群与城市化英文文献和中文翻译

  6. 轴承的摩擦与润滑英文文献和中文翻译

  7. 承载力的立足点在斜坡带...

  8. 十二层带中心支撑钢结构...

  9. 乳业同业并购式全产业链...

  10. 电站锅炉暖风器设计任务书

  11. 杂拟谷盗体内共生菌沃尔...

  12. 当代大学生慈善意识研究+文献综述

  13. java+mysql车辆管理系统的设计+源代码

  14. 酸性水汽提装置总汽提塔设计+CAD图纸

  15. 河岸冲刷和泥沙淤积的监测国内外研究现状

  16. 中考体育项目与体育教学合理结合的研究

  17. 大众媒体对公共政策制定的影响

  

About

751论文网手机版...

主页:http://www.751com.cn

关闭返回