JSP-Demos available online
Hi, the examples from my book "Java Server Pages" are now available online in two languages: German and English (Adjust your browser settings!). The source code can viewed online and is available for download. Topics covered: -- JSP scripts -- JSP standard actions -- Integration of beans -- User defined taglibs -- I18n -- Database access -- Shopping cart systems The URL is: http://shannon.informatik.fh-wiesbaden.de/buch/index.jsp volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". Some relevant FAQs on JSP/Servlets can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html http://www.jguru.com/jguru/faq/faqpage.jsp?name=JSP http://www.jguru.com/jguru/faq/faqpage.jsp?name=Servlets
Book Announcement: Java Server Pages
Book Announcement: Java Server Pages Now available: Java Server Pages By Volker Turau Publisher: dpunkt ix Edition 380 Pages ISBN 3-932588-66-5 This book provides a comprehensive in-depth treatement of web-publishing with Java Server Pages Version 1.1. It includes numerous pre-tested examples that you can use as the basis for your own JSP applications. The examples have been tested with the Tomcat and the Orion Server on Linux and Windwos NT. They are available online (including the complete source code). The book explains the life cycle of a JSP page and how the technology relates to servlets and to J2EE. What's inside: -- internationalized applications -- shopping cart -- session management -- bean based applications -- accessing databases -- JSP tag libraries -- JSP V 1.1 and Servlet V 2.2 API The book is written in German. The web-site for the book http://www.informatik.fh-wiesbaden.de/~turau/jsp/index.html has -- a complete outline of the book -- all examples online -- all examples as a WAR file -- two chapters as PDF file -- lots of usefull links to JSP resources prof. volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". Some relevant FAQs on JSP/Servlets can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html http://www.jguru.com/jguru/faq/faqpage.jsp?name=JSP http://www.jguru.com/jguru/faq/faqpage.jsp?name=Servlets
Re: GZIPing the data to the browser
Hi,
this example is from my forthcoming book on Java Server Pages
and has been test with Tomcat 3.1 and IE 4.0. Do not leave a blank
between %> and <%
<%@ page errorPage="/util/errorpge.jsp"
import="java.util.zip.*"
session="false"%><%
response.setHeader("Content-Encoding", "gzip");
GZIPOutputStream o = new GZIPOutputStream(response.getOutputStream());
String a = "GZIP ist Klasse und schnell aber .";
o.write(a.getBytes());
o.flush();
o.close();
%>
volker turau
FH Wiesbaden Fachbereich Informatik
Tel.: +49-611-9495-205 FAX +49-611-9495-210
http://www.informatik.fh-wiesbaden.de/~turau
===
To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST".
Some relevant FAQs on JSP/Servlets can be found at:
http://java.sun.com/products/jsp/faq.html
http://www.esperanto.org.nz/jsp/jspfaq.html
http://www.jguru.com/jguru/faq/faqpage.jsp?name=JSP
http://www.jguru.com/jguru/faq/faqpage.jsp?name=Servlets
New implicit objects in tags
Hi, As described in section 5.8.1 of the spec new objects (i.e. scripting variables) can be introduced though user defined tags. Question: These objects seem to have scope page, you can have NESTED, etc. but you do not have the same scoping as for Java Beans (i.e. session, application etc.). Is that true? I could insert an implicit object with public abstract void setAttribute(java.lang.String name, java.lang.Object o, int scope) into the scope I want to, but is this the correct way of doing this? volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". FAQs on JSP can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html
Accessing config parameters in jspInit()
Hi, I would like to use some configuration parameters in a JSP-page. These parameters can be accessed through the application and config object: application.getInitParameter(String), config.getInitParameter(String)). I would like to do this only once in the method jspInit(). Unfortunately in this method these objects are not available. Is this a design flaw or am I missing something? volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". FAQs on JSP can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html
Re: How to compress JSP pages using Content Encoding
You can do content encoding in jsp, I did it. Just make sure that the page
does not access the implicit variable out at all (e.g do not have blanks
outside scripts).
But I think that jsp is not the right tool to do that. The JSP-Container
should do that for you.
The code is roughly:
<%@page .><%
response.setHeader("Content-Encoding", "gzip");
GZIPOutputStream gos = new
GZIPOutputStream(response.getOutputStream());
byte[] b = " bla bla ...".getBytes();
gos.write(b);
gos.close();
%>
volker turau
FH Wiesbaden Fachbereich Informatik
Tel.: +49-611-9495-205 FAX +49-611-9495-210
http://www.informatik.fh-wiesbaden.de/~turau
===
To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST".
FAQs on JSP can be found at:
http://java.sun.com/products/jsp/faq.html
http://www.esperanto.org.nz/jsp/jspfaq.html
Re: Comments on answers to six questions on Tag Extensions (PR2)
See follow-ups intermixed indicated by >>>> | Somehow user defined tags are not discussed on this list. I think it is just lack of an implementation. >>> That might be the case, the orion application server supports JSP 1.1 >>> On the other hand, I think this is one of the outstanding features >>> of JSP and I strongly believe we will see a lot of taglibs in the >>> future. | 1. What is the return value of the methods doStartTag(), doEndTag() |respectively doAfterBody() in the support classes TagSupport and |BodyTagSupport? Note that I had mentioned SKIP_BODY, not SKIP_PAGE. >>>> That's true, sorry my fault :-( | 2. How do the implementations of doEndTag() differ in the classes |TagSupport and BodyTagSupport? | I think you misunderstood my answer. BodyTagSupports overrides both. doStartTag() changes value, while doEndTag() just uses its super, so it has the same value. >>>> Yes a misunderstanding, you should update the current javadoc >>>> documentation, because in the doc of the class BodyTagSupport under >>>> the method doAfterBody() it says >>>> "Overrides: doEndTag in class TagSupport" >>>> But the method doStartTag() is only listed under inherited from >>>> TagSupport. | 5. What happend to the method public PageContext getPageContext() in |class Tag? Why was it deleted? | Maybe a class going and playing with the page context of another class? Let me turn it around. Do you have a specific example for wanting this information? >>>> No, I was just curious. It is fine for me. Usually I try to access >>>> all information through methods. Thanks a lot for your comments!!! vt volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". FAQs on JSP can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html
Six questions on Tag Extensions (PR2)
1. What is the return value of the methods doStartTag(), doEndTag() respectively doAfterBody() in the support classes TagSupport and BodyTagSupport? 2. How do the implementations of doEndTag() differ in the classes TagSupport and BodyTagSupport? 3. Is it possible to use the method getPreviousOut() of class BodyTagSupport in the implementation of the methods doStartTag() or doEndTag() in subclasses of BodyTagSupport? Or can these methods only use pageContext.getOut()? 4. Why does the method doInitBody() in class BodyTagSupport not include the clause throws JspError? 5. What happend to the method public PageContext getPageContext() in class Tag? Why was it deleted? 6. What happened to the method public java.lang.String getTagName() in class Tag? Why was it deleted? volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". FAQs on JSP can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html
Exceptions in jspInit()
Hi, I found it awkward to catch all exceptions in the method jspInit(). Why does this method not declare that it may throw a ServletException, just as the method init()? volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". FAQs on JSP can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html
Scope of implicit objects
Hi,
According to section 2.8 of the spec version 1.1 PR implicit objects
have different scopes, e.g. request has request scope and session has
session scope. But when I test this with jswdk-1.0 I get a different
result, all implicit objects have scope page. Any ideas?
I used the following simple JSP-page to determine the scope
<%@ page import="java.util.*" session="true"%>
Implicit Objects in JSP
<% pageContext.removeAttribute("javax.servlet.jsp.jspApplication"); %>
<%!
String table(int scope, PageContext pageContext) {
Enumeration e = pageContext.getAttributeNamesInScope(scope);
if (e == null || !e.hasMoreElements()) return "No Objects";
StringBuffer result = new StringBuffer();
result.append("");
result.append("AttributClassSuperclass
Interfaces");
for (;e.hasMoreElements(); ) {
String attName = (String) e.nextElement();
Object attValue = pageContext.getAttribute(attName, scope);
if (attValue != null) {
Class cl = attValue.getClass();
Class superCl = cl.getSuperclass();
Class[] interfaces = cl.getInterfaces();
result.append("" + attName + "" + cl.getName()
+ "" + superCl.getName() + "");
if (interfaces.length == 0)
result.append(" ");
else {
for (int i = 0; i < interfaces.length-1; i++)
result.append(interfaces[i].getName() + ", ");
result.append(interfaces[interfaces.length-1].getName());
}
}
else
result.append(""+attName+"no value ");
result.append("");
}
result.append("");
return result.toString();
}
%>
<%--<%@ include file="counter.jsp" %> <%= " 5%\\>x" %> --%>
Request Scope
<%= table(javax.servlet.jsp.PageContext.REQUEST_SCOPE, pageContext)%>
Page Scope
<%= table(javax.servlet.jsp.PageContext.PAGE_SCOPE, pageContext)%>
Session Scope
<%= table(javax.servlet.jsp.PageContext.SESSION_SCOPE, pageContext)%>
Application Scope
<%= table(javax.servlet.jsp.PageContext.APPLICATION_SCOPE, pageContext)%>
volker turau
FH Wiesbaden Fachbereich Informatik
Tel.: +49-611-9495-205 FAX +49-611-9495-210
http://www.informatik.fh-wiesbaden.de/~turau
===
To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST".
FAQs on JSP can be found at:
http://java.sun.com/products/jsp/faq.html
http://www.esperanto.org.nz/jsp/jspfaq.html
Error in JSP Spec. 1.1 PR
Hi, section 7.4.1 of the JSP Spec. 1.1 PR defines the XML element type jsp:declaration as This may not be possible in all cases. Consider <%! boolean b = f[g[6]]>4; %> where f and g are arrays defined earlier. This gets translated into 4;]]> ^^^ ERROR!! An ugly solution is to split the declaration into two CDATA sections: Scriplets and expressions have the same problem. volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". FAQs on JSP can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html
Thoughts on the usage of Java Beans in JSP
Hi, I have implemented some of the components available in Microsofts ASP as Java Beans and used these components in JSP. In doing so I found that the Bean concept in JSP has severe limits. I would like to hear your opinions about my thoughts: 1. Using only the three actions useBean, setProperty and getProperty does not allow really interesting beans. Very often I wanted to invoke a method having parameters and printing the result. Printing is only possible using getProperty which does not accept parameters. It would be usefull, if this action would accept additional parameters, for example This action should be translated into: out.print(name.getPName(44)) Currently you have to do <%= name.getPName(44) %> Using this script kills one of the main advantages of beans in JSP: simple usage. If I have to use Scripts, I might as well not use getProperty and setProperty at all. But then the only thing left about beans is the notion of scope (i.e. share beans in different JSP-pages). The current versions of setProperty and getProperty encourage programmers to write access methods performing all kinds of side-effects. In doing so, some actions have to be called before others. How can you express this information to a future user of your bean? 2. Beans should have access to implicit objects such as request, response etc. Currently you have to use scripts again, for example <% name.processRequest(request, session) %> (almost all of my beans needed a similar method). It would be better if these objects would be automatically accessible to beans. How to do that? Using introspection a JSP-server could detect methods such as setRequest, setResponse etc. and invoke these method automatically while processing the action useBean. 3. In order to assign the value of a property to a scripting variable, you cannot do something like: <% int i = %> The following works: <% int i = name.getPName(); %> I thought scripts should only be the "glue" between beans. Scripts should be simple, i.e. JavaScript type. The fact that you can access a property in two ways (<%= name.getPName() %> and ) is confusing for a non programmer. SUMMARY: --- Without using scripts (i.e. java code in JSP pages) beans are only of very limited value. --- JSP developers of type "Designer" should be able to use Beans provided by JSP developers of type "Programmer" WITHOUT using scripts. --- Java code in JSP pages should be minimal, otherwise it is better to write a servelt in the first place. --- Java is too complex for a scripting language. volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". FAQs on JSP can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html
Re: XSL and Servlets?
Hi, if you want to have an online demo (including source code) of servlets using the lotus xsl processor check out: http://www.informatik.fh-wiesbaden.de/~turau/DB2XML/demo/db2xmlxslservlet.html volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". FAQs on JSP can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html
Re: jsp:setProperty
> > > > in my bean i've got a method called "public void setPs(String [] sql)" You need another public method called setPs(int i, String[] s) (in addition to the first). Then you can do sql must be of type String. You cannot assign complete arrays (as far as I know). volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". FAQs on JSP can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html
Re: question about beanName in jsp:useBean
Using beanName in jsp:useBean does not work with jswdk-1.0-ea, at least not in my applications. Any other experience? volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff JSP-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help".
Serialized Beans in JSP
Hi, I tried to use a Bean in its serialized form. I wrote a class book.SerBean which I serialized into a file called color.ser which I placed in the directory beans\book (the same directory as SerBean.class). Then I used the following JSP page Value of color: This did not work (NullPointerException). I checked the generated Java file, this did not use the value of the attribute "beanName" at all. Is this not supported in jswdk-1.0-ea? vt volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff JSP-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help".
Comments on answers to six questions on Tag Extensions (PR2)
Hi, here are some comments to the answers of Eduardo Pelegri-Llopart. Somehow user defined tags are not discussed on this list. 1. What is the return value of the methods doStartTag(), doEndTag() respectively doAfterBody() in the support classes TagSupport and BodyTagSupport? The values you mention in your mail are not documented. The orion application server behaves as follows: TagSupport: doStartTag() returns EVAL_BODY_INCLUDE (and not SKIP_PAGE) doEndTag()returns EVAL_PAGE 2. How do the implementations of doEndTag() differ in the classes TagSupport and BodyTagSupport? It seems odd that BodyTagSupport overrides doEndTag but does not override doStartTag. Since these classes will be subclassed by users, overriding doEndTag() by super.doEndTag() is even more odd. 3. Is it possible to use the method getPreviousOut() of class BodyTagSupport in the implementation of the methods doStartTag() or doEndTag() in subclasses of BodyTagSupport? Or can these methods only use pageContext.getOut()? Using getPreviousOut() seems logical. Appartently the orion server reports an error when doing so. 4. Why does the method doInitBody() in class BodyTagSupport not include the clause throws JspError? Bug in PR2, ok 5. What happend to the method public PageContext getPageContext() in class Tag? Why was it deleted? Providing pageContext as a protected field doesn't seem to be consistent with the other J2EE APIs. There only very few protected fields in these classes. Why did you choose pageContext as one of them? Why is it safer? 6. What happened to the method public java.lang.String getTagName() in class Tag? Why was it deleted? I used it only for error reporting (as you mentioned). I found it usefull, because introducing the tag name in the tag handler class makes it harder to change tag names (it is redundant). Also if you subclass tag handlers error reporting using getTagName() was easy. Thanks for answering my questions! :-) volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". FAQs on JSP can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html
Comments on the SQL Tags and example source code (PR2)
Hi, I tested the example source code for the SQL tags using the orion application server. I am aware the stuff is only included for pedagogical reasons. I found it usefull to experiment with the code. There are a few things I had to change: -- ConnectionTag and QueryTag are using DefaultTEI as their teiclass. This is not possible, because the class names of the variables cannot be String (as in DefaultTEI). They must be java.sql.Connection respectively java.sql.ResultSet. This raises the question if the concept of TagExtraInfo classes is really so useful. The classes ConnectionTEI and QueryTEI I had to introduce are almost identical. -- The constructor of ConnectionTag needs to load a JDBC driver. -- There is an inconsistency between the PR2 documentation and the sample source code: On page 133 the tag has an attribut iterate with value row. In the source code the attribute's name is row. Also on this page the methods getAccount() and getBalance() have to be changed to getString(1) or something similar. -- I could not use the query select OrderDate from orders where ORDERID < 11061 because of the character < in the query. Any ideas how to protect these characters? After changing this minor details the examples worked. Has anybody comments or experience with these tags or designed different db tags? volker turau FH Wiesbaden Fachbereich Informatik Tel.: +49-611-9495-205 FAX +49-611-9495-210 http://www.informatik.fh-wiesbaden.de/~turau === To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST". FAQs on JSP can be found at: http://java.sun.com/products/jsp/faq.html http://www.esperanto.org.nz/jsp/jspfaq.html
