Charmy Madhvani

I came across a question

5
Marks: 1 Which of the following statements are true?
Choose at least one answer.
a. Tag files can contain the tag element that allows attributes to be processed
b. tag files cannot process attributes from the calling jsp page
c. the body of a tag file cannot contain scripting
d. the body of a tag file cannot contain EL statements
e. the body of a tag file can be declared as tagdependent
Partially correct
Marks for this submission: 1/1.

My Ans was partially correc because the right answers for me were a and e. But the Actual answer were a,c,e.
Just wanted to know how c is correct.
Infact in HFSJ it is clearly written on page 500 in one of the Dumb Question

You can do scripting in tag file but not in the body of the tag used to invoke tag file

Am I right or am I confused?

Which of the following statements are true?
Choose at least one answer. a. Once an ServletRequest attribute has been set, it is visible to all subsequent requests
b. Data in a HttpSession attribute will not be available if the web server restarts
c. Data in the ServletContext can be shared by any servlet of the same web application.
d. The getParameter method of HttpSession will retrieve a session attribute

I answered both b and c but the correct one is only c. b is incorrect for following reason:Although session attribute data may dissapear if Tomcat is restarted, this is not guaranteed behaviour and some web servers may store session data in a database.

Which web server stores the session attribute even after restarted? And whats the point in retaining the session data once the session is invalidated?

So should I say that Filter's doFilter method is a callback method but FilterChain's doFilter method is an inline?

Hi I have come across the terms callback and inline in Filters chapter. Just wanted to know the definitions of each.

Whether the following methods are callback or not?

doGet,doPost,init and destroy(both in Filters and jsps/servlets), doFilter

Any examples of inline methods?

Because jsp documents does not support scripting . It has a special tag for declaration which is mentioned in your option 'a'.

it started working now, for 2 reasons:
1. I added <type>java.util.List</type> for <attribute> element in tld for clist.
2. I added clist in session and passed it to the tag from sessionScope.

But my question remains that if i declare that list in scripting why should'nt it take from page scope. I explicitly have to add it in any of the scope.

Also
<c:set var="clist" scope="session"> Red,Blue,Indigo,Yellow,Green </c:set>

creates a List. Then why it is giving me an error :

Attempt to convert String "Red,Blue,Indigo,Yellow,Green" to type "java.util.List", but there is no PropertyEditor for that type

ok..got your point. Thanks

mList was my mistake.
and c list is declared within that jsp page only. So I assume it is of page scope

why E is not correct (ServletRequestListner).

Hi.
I a getting error when I run following code

<br> <% List clist=new ArrayList(); clist.add("Red"); clist.add("Blue"); clist.add("Indigo"); %> <mySimpleTag:simple2 subTitle="The colors of rainbow are:" colorList="${mlist}"> ${color} </mySimpleTag:simple2 > <br>

<uri>simpleTags</uri> <tag> <description>tag with body</description> <name>simple2</name> <tag-class>com.example.model.BodyTagTest1</tag-class> <body-content>scriptless</body-content> <attribute> <name>subTitle</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> <attribute> <name>colorList</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> </tag>

public class BodyTagTest1 extends SimpleTagSupport { private String subTitle; private List colorList; public void setSubTitle(String subTitle) { this.subTitle=subTitle; } public void setColorList(List colorList) { this.colorList=colorList; } public void doTag() throws JspException,IOException { Iterator i=colorList.iterator(); while(i.hasNext()) { String c=i.next().toString(); getJspBody().invoke(null); } } }

It is getting null pointer exception..I dont understand why.
ALso when I avoid scripting to use
<c:set var="clist"> Red,Blue,Indigo,Yellow,Green </c:set>

I am getting the error that it cannot convert String to List.
In jsp itself I can use this variable as List. But why cant it be passed as a List in the TagHandler. Please help me

Thanks..Its working now..

Hi,
I am trying to put a classic tag in my jsp similar to HFSJ on page 521. But its giving me error that it cannot find the tag handler class

An error occurred at line: 15 in the jsp file: /classicTagUse.jsp
The type com.example.model.ClassicTest1 is not visible

My code is as follows
*******************************TLD************************************
<uri>classicTags</uri> <tag> <description>Use of classsic tags</description> <name>clc</name> <tag-class>com.example.model.ClassicTest1</tag-class> <body-content>empty</body-content> </tag> </taglib>
**********************************************************************

***************************JSP****************************************
<%@ page import="java.util.*"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <%@ taglib prefix="myclassic" uri="classicTags" %> <HTML> <HEAD> <TITLE> Advice page </TITLE> </HEAD> <BODY> <p>Welcome to the Classic Tags page page</p> <br> <br> <myclassic:clc /> </BODY> </HTML>
*******************************************************************

**************************TagHandler*******************************
package com.example.model; import javax.servlet.jsp.*; import javax.servlet.jsp.tagext.*; import java.io.*; class ClassicTest1 extends TagSupport { public int doStartTag() throws JspException { JspWriter out=pageContext.getOut(); try{ out.println("Congarts, you have successfully implemented classic tag");}catch(IOException ex){ throw new JspException("IOException-"+ex.toString()); } return SKIP_BODY; } }
***********************************************************************

Any mistake in my code?

I'll take care next time. Thanks anyways

Can you achieve this code without using scriplet?
users.add("Paul"); users.add("Kathy"); users.add("Frank");

my tld file is as follows:
<uri>CalcFunctions</uri> <funtion> <name>addIt</name> <funtion-class>com.example.model.Calculator</funtion-class> <funtion-signature>int add(int,int)</funtion-signature> </funtion> <funtion> <name>subtractIt</name> <funtion-class>com.example.model.Calculator</funtion-class> <funtion-signature>int subtract(int,int)</funtion-signature> </funtion> <funtion> <name>multiplyIt</name> <funtion-class>com.example.model.Calculator</funtion-class> <funtion-signature>int multiply(int,int)</funtion-signature> </funtion> <funtion> <name>sayhi</name> <funtion-class>com.example.model.Calculator</funtion-class> <funtion-signature>java.Lang.String sayHi()</funtion-signature> </funtion>

please help me correcting this code if it is wrong