Trouble getting examples to work

John Najarian Sun, 05 Sep 2004 08:25:06 -0700

I’m trying some of the examples from the

http://java.sun.com/developer/technicalArticles/javaserverpages/JSP20/ site.

Trying the 1 below the error message I get:

Anyone have any ideas? Thanks

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: The absolute uri: http://jakarta.apache.org/tomcat/jsp2-example-taglib %>

<HEAD>

<TITLE>Functions</TITLE>

</HEAD>

<BODY>

<H3>Add Numbers</H3>

<P>

<FORM action= "" be resolved in either web.xml or the jar files deployed with this application

        org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:50)

        org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:409)

        org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:118)

        org.apache.jasper.compiler.TagLibraryInfoImpl.generateTLDLocation(TagLibraryInfoImpl.java:316)

        org.apache.jasper.compiler.TagLibraryInfoImpl.<init>(TagLibraryInfoImpl.java:147)

        org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:418)

        org.apache.jasper.compiler.Parser.parseDirective(Parser.java:483)

        org.apache.jasper.compiler.Parser.parseElements(Parser.java:1539)

        org.apache.jasper.compiler.Parser.parse(Parser.java:126)

        org.apache.jasper.compiler.ParserController.doParse(ParserController.java:220)

        org.apache.jasper.compiler.ParserController.parse(ParserController.java:101)

        org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:203)

        org.apache.jasper.compiler.Compiler.compile(Compiler.java:470)

        org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)

        org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)

        org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511)

        org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:295)

        org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)

        org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)

        javax.servlet.http.HttpServlet.service(HttpServlet.java:802)


note The full stack trace of the root
cause is available in the Apache Tomcat/5.0.27 logs.

 

 

Figure
2: Handling forms 

Developing
and Using Functions

The
_expression_ language allows you to define functions that can be invoked in an
_expression_. Functions must be programmed as a public static
method in a public
class. Once the function is developed, its signature is mapped in a Tag Library
Descriptor (TLD). 

To
illustrate the use of functions, I use a simple example to add two numbers.
First we write the Java code for the method to add two numbers. Code Sample 3
shows a static method that accepts two Strings,
parses them to integers, and returns their sum. 

Code Sample 3: Compute.java 


 
  package jsp2.examples.el;
 
import java.util.*;
 
public class Compute {
   public static int add(String x, String y) {
      int a = 0;
      int b = 0;
      try {
        a = Integer.parseInt(x);
        b = Integer.parseInt(y);
      }catch(Exception e) {} 
      return a + b;
   }
}
 










Once this
is successfully compiled using javac,
the next step is to map the function's signature in the tag library. Code
Sample 4 shows how to map the add function to the class
containing the implementation of the function and the signature of the
function. I will tell you where to add this later. 

Code Sample 4: Function Descriptor 


 
      <function>
        <description>add x and y</description>
        <name>add</name>
        <function-class>jsp2.examples.el.Compute
            </function-class>
        <function-signature>int
            add(java.lang.String,java.lang.String)
                </function-signature>
    </function>
 










Now, we
can write the JSP page that uses the function. Code Sample 5 shows a form with
two fields. The user enters two numbers and when the "Add Numbers"
button is clicked, the function is called to add the numbers. The result is
displayed on the same page. 

Code Sample 5: math.jsp 


 
  <%@ taglib prefix="my" 
    uri="http://jakarta.apache.org/tomcat/jsp2-example-taglib %>
 
<HEAD>
<TITLE>Functions</TITLE>
</HEAD>
 
<BODY>
 
<H3>Add Numbers</H3>
<P>
<FORM action="" method="GET">
   X = <input type="text" name="x" value="${param["x"]}">
   <BR>
   Y = <input type="text" name="y" value="${param["y"]}">
   <input type="submit" value="Add Numbers">
</FORM>
 
<P>
The sum is: ${my:add(param["x"],param["y"])}
 
</BODY>
</HTML>
 










To run
this example: 


 Copy Compute.java
     and save it at: C:\Tomcat5.0\webapps\jsp-examples\WEB-INF\classes\jsp2\examples\el
 Compile Compute.java
     using javac
 Edit the file C:\Tomcat5.0\webapps\jsp-examples\WEB-INF\jsp2\jsp2-example-taglib.tld
     and append the snippet of code in Code Sample 4 after the last </function>
     in the file and before </taglib>
 Copy math.jsp
     to c:\Tomcat5.0\webapps\jsp-examples\jsp2-tutorial
 Request the jsp file math.jsp
     from a web browser


If all
goes well, you should see something similar to Figure 3.

Trouble getting examples to work

HTTP Status 500 -

Developing and Using Functions

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