How to call a function from Java to JSP

Question

Hello,
I have a question about using tags.
I have a java file,which has a function. Now I want to call this function into my JSP page.
I'm using JSP 1.2 and TOMCAT 4.1 with Java2 SDK.
I search through the web and find a method to do this.Bu it requires JSP 2.0
But I try that in my machine(using JSP 1.2).It gives an error:
Did you know what is the error? Or is there any method to call a function into my JSP page?
Please, help me to solve this.
Here are my codes(part of them)
UserPassword.java file
package data;
import java.io.*;
import java.sql.*;
import java.util.*;
import javax.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class UserPassword
     public static String verify(String username,String password){
          // some codes
<?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE taglib
        PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
     "http://java.sun.com/j2ee/dtd/web-jsptaglibrary_1_2.dtd">
<taglib>
  <tlib-version>1.0</tlib-version>
  <jsp-version>1.2</jsp-version>
  <short-name>simple</short-name>
  <uri>http://jakarta.apache.org/tomcat/HRM/WEB-INF/lib</uri>
  <description>
     A  tab library for the login
  </description>
<function>
        <description>verify username and password</description>
        <name>verify</name>
        <function-class>data.UserPassword</function-class>
        <function-signature>String verify(java.lang.String,java.lang.String)
        </function-signature>
</function>
</taglib>I put this file into the webapps/HRM/WEB-INF/lib folder
Here is my JSP file.
<%@ page language="java" %>
<%@ page import="data.UserPassword" %>
<%@ page session="true" %>
<%@ taglib prefix="login" uri="/WEB-INF/lib/LoginVerify.tld" %>
<jsp:useBean id="useraccount" class="data.UserPassword"/>
<jsp:setProperty name="useraccount" property="*"/>
<%
String status = UserPassword.verify(String username,String password);
String nextPage = "MainForm.jsp";
if(status.equals("InvalidU")) nextPage ="InvalidUserName.jsp";
if(status.equals("InvalidP")) nextPage ="InvalidPassword.jsp";
if(status.equals("main")) nextPage ="MainForm.jsp";
%>
<jsp:forward page="<%=nextPage%>"/>
Here is the error:
org.apache.jasper.JasperException: XML parsing error on file /WEB-INF/lib/LoginVerify.tld: (line 18, col -1): Element "taglib" does not allow "function" here.
     at org.apache.jasper.xmlparser.ParserUtils.parseXMLDocument(ParserUtils.java:189)
     at org.apache.jasper.compiler.TagLibraryInfoImpl.parseTLD(TagLibraryInfoImpl.java:247)
     at org.apache.jasper.compiler.TagLibraryInfoImpl.(TagLibraryInfoImpl.java:183)
     at org.apache.jasper.compiler.Parser.parseTaglibDirective(Parser.java:354)
     at org.apache.jasper.compiler.Parser.parseDirective(Parser.java:381)Please, help me to solve this trouble.
Thanks.

Answer 1

Yes. As serlank showed, you can just call the function easily in scriptlet tags
However the whole point of a tag library is to avoid the use of scriptlets.
Seeing as you can't use functions, is just to do it as a standard tag.
ie in your jsp
<login:verify name="<%= userName %>" password = "<%= password %>" resultVar = "status"/>
<c:choose>
  <c:when test="${status == 'InvalidU'}">
    <c:set var="nextPage" value="InvalidUserName.jsp"/>
  </c:when>
  <c:when test="${status == 'InvalidP'}">
    <c:set var="nextPage" value="InvalidPassword.jsp"/>
  </c:when>
</c:choose>In your case, this tag in the tld would possibly look something like this.
You would then have to write a tag handler class that would call the function you want.
<tag>
  <name>verify</name>
  <tagclass>com.tags.login.Verify</tagclass>
  <teiclass>com.tags.login.VerifyTEI</teiclass>  (if required)
  <bodycontent>JSP</bodycontent>
// name attribute 
<attribute>
      <name>name</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
// password attribute
    <attribute>
      <name>password</name>
      <required>true</required>
      <rtexprvalue>true</rtexprvalue>
    </attribute>
// result variable to return a response from the tag.
  <variable>
    <name-from-attribute >resultVar</name-from-attribute >
    <variable-class>java.lang.String</variable-class>
    <declare>true</declare>
    <scope>AT_END</scope>
  </variable>
</tag>Hope this helps some, and doesn't confuse too much :-)
Cheers,
evnafets