Jason, I believe you can use the type attribute instead of class to indicate that the bean should not be instantiated. (This is an old reference, but I think it's still accurate on the topic: http://java.sun.com/products/jsp/syntax/1.0/syntaxref10.fm14.html.)
-john. -----Original Message----- From: Remy Maucherat [mailto:[EMAIL PROTECTED] Sent: Monday, January 12, 2004 3:08 PM To: Tomcat Users List Subject: Re: Tomcat 5.0.16 jsp:useBean of type java.util.List won't compile Jason Wilson wrote: > I have some jsp pages that now break in Tomcat 5.0.16. > In particular, my use of the jsp:useBean tag is no > longer working, it fails to compile. > > ## <jsp:useBean id="myListBean" scope="session" > class="java.util.List"/> > > In the generated servlet, it attempts to do a > > ## java.util.List myListBean = new java.util.List(); > > which does not work, since it is not a concrete class. > > In the version of Tomcat I was working with (4.1.*), > it didn't use a hard coded constructor, for example: > > ## myListBean = (java.util.List) > java.beans.Beans.instantiate(this.getClass().getClassLoader(), > "java.util.List"); > > Using reflection to call the constructordid not create > a compile time error. This was good, in any case, > because my JSP is never supposed to instantiate these > beans, they are created by a servlet that forwards the > request to them. > > Does anyone know why this new JSP servlet generator > uses this type of constructor? It seems like it would > break A LOT of code out there, where a JPS page uses > the useBean to get a bean that is supposed to already > be existing in the specified scope. Or are we > supposed to only put concrete objects in our class > types, and only those that have a no-arg constructor? > > Is there something new in the jsp 2.0 spec that allows > me to define a bean that will never be instantiated in > the page itself? > > My workaround is to remove all the jsp:useBean tags > and just use scriptlets to get at the objects. > > ## <% java.util.List myList = (java.util.List) > session.getAttribute("myList"); %> > > Once again, is there anyway that I can use jsp:useBean > with classes like java.util.List or even classes that > I have written that do not provide a no-arg > constructor? I did run into this issue, and the classes of the objects specified in useBean *must* be JavaBeans (I did check the specification). So this means, indeed, a concrete class with a no arg constructor. > ## myListBean = (java.util.List) > java.beans.Beans.instantiate(this.getClass().getClassLoader(), > "java.util.List"); would create an error at runtime. I think the compile time error is more honest and prevents sloppy coding, so I did go in and changed some JSP code from JBoss management pages. Yes, I know, the code is never supposed to be run blabla, but still, bugs do happen ;-) -- xxxxxxxxxxxxxxxxxxxxxxxxxxxxx Rémy Maucherat Senior Developer & Consultant JBoss Group (Europe) SàRL xxxxxxxxxxxxxxxxxxxxxxxxxxxxx --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
