What's the bug?
You can't instanciate an abstract class in java.
You can't instanciate an array in java without dimensioning it.
On Tuesday 20 January 2004 12:15 pm, Andrew Schwimmer wrote:
> Summary:
> Code that worked in Tomcat4 throws a compile time exception in Tomcat5.
>
>
> My Jsp file consists of one line.
> <jsp:useBean scope="request" id="l" class="java.util.List"/>
>
> In Tomcat 4 a line like this was legal. If "l" did not exist in the request
> scope it would try to instantiate it and throw a runtime
> java.lang.InstantiationException. However in Tomcat 5 it causes this
> compile time exception.
>
> org.apache.jasper.JasperException: Unable to compile class for JSP
>
> An error occurred at line: 1 in the jsp file: /useBeanTest.jsp
>
> Generated servlet error:
> [javac] Compiling 1 source file
>
> C:\jakarta-tomcat-5.0.16\work\Catalina\localhost\jsp-examples\org\apache\js
>p \useBeanTest_jsp.java:44: java.util.List is abstract; cannot be
> instantiated l = new java.util.List();
> ^
> 1 error
>
>
>
> org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandl
>e r.java:127)
>
> org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:
>3 51)
> org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:415)
> org.apache.jasper.compiler.Compiler.compile(Compiler.java:458)
> org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)
>
> org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:
>5 52)
>
> org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:
>2 91)
> org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
> org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
> javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
>
> The code generated in Tomcat5 is
>
> java.util.List l = null;
> synchronized (request) {
> l = (java.util.List) pageContext.getAttribute("l",
> PageContext.REQUEST_SCOPE);
> if (l == null){
> l = new java.util.List();
> pageContext.setAttribute("l", l, PageContext.REQUEST_SCOPE);
> }
> }
>
> The code generated in Tomcat4 is
>
> java.util.List l = null;
> synchronized (request) {
> l = (java.util.List) pageContext.getAttribute("l",
> PageContext.REQUEST_SCOPE);
> if (l == null){
> try {
> l = (java.util.List)
> java.beans.Beans.instantiate(this.getClass().getClassLoader(),
> "java.util.List");
> } catch (ClassNotFoundException exc) {
> throw new InstantiationException(exc.getMessage());
> } catch (Exception exc) {
> throw new ServletException("Cannot create bean of class " +
> "java.util.List", exc);
> }
> pageContext.setAttribute("l", l, PageContext.REQUEST_SCOPE);
> }
> }
>
>
> Which throws the exception because you aren't allowed to instantiate an
> abstract class.
>
> --------------------------------------------------------------------
>
> A similar exception is being thrown if you attempt to retrieve an array.
>
> A line in a jsp...
> <jsp:useBean scope="request" id="l" class="java.util.ArrayList[]"/>
>
> Yields an exception...
>
> org.apache.jasper.JasperException: Unable to compile class for JSP
>
> An error occurred at line: 1 in the jsp file: /useBeanTest2.jsp
>
> Generated servlet error:
> [javac] Compiling 1 source file
>
> C:\jakarta-tomcat-5.0.16\work\Catalina\localhost\jsp-examples\org\apache\js
>p \useBeanTest2_jsp.java:44: array dimension missing
> l = new java.util.ArrayList[]();
> ^
> 1 error
>
>
>
> org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandl
>e r.java:127)
>
> org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:
>3 51)
> org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:415)
> org.apache.jasper.compiler.Compiler.compile(Compiler.java:458)
> org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)
>
> org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:
>5 52)
>
> org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:
>2 91)
> org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
> org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
> javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
>
> In this case the code generated in Tomcat5 is
> java.util.ArrayList[] l = null;
> synchronized (request) {
> l = (java.util.ArrayList[]) pageContext.getAttribute("l",
> PageContext.REQUEST_SCOPE);
> if (l == null){
> l = new java.util.ArrayList[]();
> pageContext.setAttribute("l", l, PageContext.REQUEST_SCOPE);
> }
> }
>
> The code generated in Tomcat4 is
>
> java.util.ArrayList[] l = null;
> synchronized (request) {
> l = (java.util.ArrayList[]) pageContext.getAttribute("l",
> PageContext.REQUEST_SCOPE);
> if (l == null){
> try {
> l = (java.util.ArrayList[])
> java.beans.Beans.instantiate(this.getClass().getClassLoader(),
> "java.util.ArrayList[]");
> } catch (ClassNotFoundException exc) {
> throw new InstantiationException(exc.getMessage());
> } catch (Exception exc) {
> throw new ServletException("Cannot create bean of class " +
> "java.util.ArrayList[]", exc);
> }
> pageContext.setAttribute("l", l, PageContext.REQUEST_SCOPE);
> }
> }
>
>
> If this should be in the Tomcat-Dev list, I'm sorry and I'll move it there.
> If this has already been brought up as I bug in Tomcat5, sorry for bringing
> it up again but I couldn't find any mention of it in Bugzilla.
>
> Thanks for reading.
>
> -Andrew.
>
>
>
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--
Ben Souther
F.W. Davison & Company, Inc.
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