作者：jspfuns
日期：2000-8-10 17:48:55
Java Server Pages Frequently Asked Questions 


Maintainer: Richard Vowles, rvowles@esperanto.org.nz (http://www.esperanto.org.nz)



Questions
What is JSP? 
What version is the current version of JSP? 
Where can I get the specification for JSP? 
Who supports JSP? 
What books are available for JSP? 
Is JSP better than ASP (Microsoft's Active Server Pages)? 
What HTML editors support JSP? 
Yes, but how does it perform? 
How to invoke a JSP page directly from by browser? 
How do you invoke a JSP page from a servlet? 
How do you pass data (including beans) to a JSP from a servlet? 
How can I pool connections to my database? 
How do I use other languages in my JSP? 
How can I set a cookie in JSP? 
Can JSP and Servlet share same Session and Beans? 
How do I plug JSP into Microsoft's IIS Web Server? 
Are there any newsgroups that discuss JSP? 
What do the differing levels of bean storage (page, session, app) mean? 
Where can I find the mailing list archives? 
What are the important steps in using JDBC in JSP? 
How does variable scope work in JSP? 
How do I forward to an HTML page? 
Are there any white papers or documents explaining how JSP fits? 
How to I create dynamic GIFs for my JSP? 
Do you know where I could get some code that would encode something to the HTML DTD standard? 
What is page compilation? 
How are servlets and JSP pages related? 
Any good web sites for up to date activities in the Java/JSP/Servlet world? 
How do I force a user to log in? 
So how can a newbie get started with JSP? 
How can I ensure that session objects stay in existence when the web server restarts? 
How can I include one JSP inside another JSP? 
Is there some sort of event that happens when a session object gets bound or unbound to the session? 
Is there a way to execute a JSP from the comandline or from my own application? 
What should I use, Model 1 or Model 2? 
How do I delete a cookie with JSP? 
Are there tips on things to watch out for in JSP? 
How do you get started with JSP on the Macintosh? 
What Application Servers support JSP? 
What happened to the LOOP and DISPLAY tags from JSP 0.92? 
Does JSP have a bean providing File Upload features like ActiveX upload control? 
So how do I use EJB from JSP? 
Can I just abort processing a JSP? 
"I'm trying to pass an object between a servlet and a JSP page, but my object is null on the JSP page. What could be wrong?" 




1) What is JSP? TOC 


JSP is a dynamic scripting capability for web pages that allows Java as well as a few special tags to be embedded into a web file (HTML/XML, etc). The suffix traditionally ends with .jsp to indicate to the web server that the file is a JSP file. JSP is a server side technology - you can't do any client side validation with it.

JSP files actually get compiled into Servlets, so what is the point? Why not just write Servlets?

For most people, the benefit is twofold:

The focus is on HTML. Java and the JSP extensions assist in making the HTML more
functional. Servlets on the other hand allow outputting of HTML but it is a tedious
process. 
It is easy to make a change and then let the JSP capability of the Web Server you are
using deal with compiling it into a Servlet and running it. 
In the past, people have used servlets because of the problem of redirection - because by the time the JSP engine gets around to writing information back down the HTTP pipe, you could not do a redirect effectively in JSP - leading to the concepts of Model 1 vs Model 2 (see question 38). This has been fixed in JSP 1.0 with the addition of buffered output streams.

JavaSoft also has a FAQ, covering different questions, and it is located at http://java.sun.com/products/jsp/faq.html.

2) What version is the current version of JSP? TOC 



The current version of JSP is 1.1. It is available from http://java.sun.com/products/jsp.

The JSP 1.1 is available from http://java.sun.com/products/jsp/techinfo.html.

The 0.92 spec is available from http://java.sun.com/products/jsp/jsp092.html

The 0.91 spec is a popular version though, and much software that supports the JSP pre-standard actually supports 0.91 of JSP.

The 0.91 spec is available from http://www.burridge.net/jsp/Spec91/jsp_spec.html

3) Where can I get the specification for JSP? TOC 



You can get the current spec from http://java.sun.com/products/jsp. This is along with the reference implementation which works with its own web server.

4) Who supports JSP? TOC 



There are the following implementations available:

Name 
Version of JSP Supported 
Cost 
Comments 
JSP Reference 1.1 free TOMCAT - Now included as part of the J2EE Reference Implementation, but also managed by the Jakarta Project as part of Apache. This implementation has a way to go before being ready for production. 
GNU JSP 1.0 free, open source, located in CVS at the Giant Java Tree 
Sun's Java Web Server 2.0 1.0 commercial Sun's own Java Web Server. Being replaced with iPlanet (Alliance) 
PolyJSP 0.92 free, open source PolyJsp is based on XML/XSL and has been designed to be extensible. Now supports WebL Hasn't been updated for a while. 
Resin 1.0, 1.1 in beta Unknown Now Open Source. 
SJSP 1.1 free for personal use Uses compile time introspection, allows you to replace your existing JSP engine in your web server. 
zJSP 0.91 Last updated, Sept 3, 1998 
JRUN 0.92, 1.0 commercial JSP 1.1 support now in beta. 
Orion 1.1 commercial Orion is a web application server that implements JSP internally. It also has a lot of JSP vs other JSP and vs ASP stats on its pages. Also supports Servlet 2.2 
ServletExec 1.1 commercial Supports large number of web servers 
RocketJSP 1.0 GPL Located in the Giant Java Tree 




5) What books are available for JSP? TOC 



There are now a number of books available on JSP from various publishers.

A quick search of Amazon comes up with

Professional Java Server Programming: with Servlets, JavaServer Pages (JSP), XML, Enterprise JavaBeans (EJB), JNDI, CORBA, Jini and Javaspaces 
Professional Java XML Programming with servlets and JSP 
Pure JSP Java Server Pages 
Web Development with JavaServer Pages 
There is a group of people working on a Web book for JSP - information is located at http://www.esperanto.org.nz/jspbook. There is another at http://www.aptura.com/technology/jspBook_Architectures.html and yet another at Brainopolis.

6) Is JSP better than ASP (Microsoft's Active Server Pages)? TOC 



This is a matter of great debate. Many punters think that JavaSoft has the benefit of hindsight - what works well and what does't. ASP is very complex but supports multiple scripting languages and the ActiveX model of Microsoft. Although ASP _is_ available on many platforms, the ActiveX library support that makes it as powerful as it is is missing and thus makes ActiveX only feasible for an NT platform.

According to recent statistics (see the RedHat site), 22% of web servers are NT, (21% are Linux), that means there is 78% needing something else, and JSP advocates believe that JSP fits the bill nicely that you very much.

7) What HTML editors support JSP? TOC 



Most of the visual developers do not support JSP in any way, shape or form, they mess up the tags totally. 

The following HTML editors have been known to work with JSP:


Product 
Location 
Comments 
HomeSite http://www.allaire.com/ JSP colour coding will be in HS 4.0.1, but you can get a plug in now from http://www.burridge.net/jsp/homesite.html 
NetObjects ScriptBuilder 3.0 http://www.netobjects.com/products/html/nsb3.html Win32 product supports JSP 
Any text editor 
Borland JBuilder 3.5 http://www.borland.com/jbuilder Java Development tool, supports JSP internally, and allows running and debugging of JSPs 
DreamWeaver 3 http://www.dreamweaver.com/ Ignores JSP tags, and allows you to edit JSP files as if they are HTML files given you customise the product slightly (you need to edit a special file) 
FrontPage 2000 http://www.microsoft.com/frontpage Some reports that Front Page now ignores JSP tags. 



8) Yes, but how does it perform? TOC 



I have been picking up some comments:

Brian Burridge, brian_burridge@VALPAK.COM
"Our extranets for 300 franchises, 500+ users, our Intranet for thousands of employees, 
and eventually all of our other web sites. New Atlanta has been running for 6 weeks 
now without even one problem. Programming in JSP has turned out to be as easy as Perl, 
yet all our tests show it to be up to 10x faster."
Also available are a set of benchmarks from the people who make the Orion server, located at http://orion.evermind.net/, and also from the people who do Resin (comparing their JSP implementation with Orion)

9) How to invoke a JSP page directly from by browser? TOC 



JSP files are just like HTML files, so if your index.jsp file is in your root directory of your web site, use http://localhost/index.jsp