Solved

JSP Call to Bean Getter Malfunction

Posted on 2004-08-25
9
338 Views
Last Modified: 2012-05-05
I am not understanding something about calling bean methods from JSP.  All calls to the bean "getter" return nothing!  Here's my jsp...

   <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
   <HTML>
   <HEAD>
   <TITLE>Reusing JavaBeans in JSP</TITLE>
   </HEAD>
   <BODY>
   <jsp:useBean id="test" class="myBeans.SimpleBean"/>
   <jsp:setProperty name="test" property="message" value="Hello WWW" />
   Message 1:  <jsp:getProperty name="test" property="message" />
   <br>
   <% test.setMessage("New Message"); %>
   Message 2: <jsp:getProperty name="test" property="message" />
   <br>
   Message 3: <% test.getMessage(); %>
   <br>
   <jsp:setProperty name="test" property="message" value="Final Message" />
   Message 4-1: <% test.getMessage(); %>
   <br>
   Message 4-2: <jsp:getProperty name="test" property="message" />
   </BODY>
   </HTML>

Here's my bean class...
   
   package myBeans;
      public class SimpleBean
   {
       private String message = "No message specified";
          public String getMessage()
       {
       return(message);
       }
          public void setMessage(String message)
       {
       this.message = message;
       }
   }
   
 (By the way, I created a test class with a main method and successfully tested calls to setMessage and getMessage.)

Here's my output...
 
   Message 1: Hello WWW
   Message 2: New Message          <-- proof that test.setMessage call worked...
   Message 3:                               <-- call to test.getMessage() failure...
   Message 4-1:                            <-- call to test.getMessage() failure...
   Message 4-2: Final Message

Nothing prints for Message #3 and #4-1 above.  Why?  The commonality is that both call test.getMessage().

Recently, I asked a question about using beans.  My problem ended up being path related.  This question is different than my previous question, but you can refer to http://www.experts-exchange.com/Web/Web_Languages/JSP/Q_21106099.html if I haven't provided enough background info above.
0
Comment
Question by:LarryAndro
  • 4
  • 2
  • 2
  • +1
9 Comments
 
LVL 19

Accepted Solution

by:
ramazanyich earned 230 total points
ID: 11892445
Use <%=test.getMessage()%>
0
 
LVL 27

Assisted Solution

by:rrz
rrz earned 20 total points
ID: 11892492
><% test.getMessage(); %>
Please use  instead
<%=test.getMessage()%>    rrz
0
 
LVL 27

Expert Comment

by:rrz
ID: 11892503
Sorry ramazanyich I didn't see your post.
0
Best Practices: Disaster Recovery Testing

Besides backup, any IT division should have a disaster recovery plan. You will find a few tips below relating to the development of such a plan and to what issues one should pay special attention in the course of backup planning.

 
LVL 1

Author Comment

by:LarryAndro
ID: 11892715
I initially tried <%=...%> as you both suggested and it didn't work.  So, I tried <%...%>, as you saw in my first message.  When I changed back to <%=...%> as suggested, it still didn't work.  Here's the error I got...

   C:\Tomcat_JWSDP_1.4.1.0\work\Catalina\localhost\SCS_Prototype\org\apache\jsp\SimpleBean_jsp.java:71: ')' expected out.print(test.getMessage(););

But, I noticed you didn't append a semicolon to <%=test.getMessage();%> like I did.  So, I removed my semicolon to make it exactly match your suggestion(s), and it worked.

Here's the working code...

   <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
   <HTML>
   <HEAD>
   <TITLE>Reusing JavaBeans in JSP</TITLE>
   </HEAD>
   <BODY>
   <jsp:useBean id="test" class="myBeans.SimpleBean"/>
   <jsp:setProperty name="test" property="message" value="Hello WWW" />
   Message 1:  <jsp:getProperty name="test" property="message" />
   <br>
   <% test.setMessage("New Message"); %>
   Message 2: <jsp:getProperty name="test" property="message" />
   <br>
   Message 3: <%=test.getMessage()%>
   <br>
   <jsp:setProperty name="test" property="message" value="Final Message" />
   Message 4-1: <%= test.getMessage() %>
   <br>
   Message 4-2: <jsp:getProperty name="test" property="message" />
   </BODY>
   </HTML>

But, now I'm mystified about the use or non-use of semicolons!  There are two locations in the above code I am referring two:

   (1) <% test.setMessage("New Message"); %>
   (2) <%= test.getMessage() %>

If I remove the semicolon from #1 I get an "expected semicolon" error.  If I add a semicolon to #2, I get an error!

What are the rules?  (Add semicolon if code is being executed, and don't if output is being returned?)
0
 
LVL 19

Assisted Solution

by:ramazanyich
ramazanyich earned 230 total points
ID: 11892816
As you know JSP pages during request converted to Java source and compiled.
<% %> in JSP are used to insert Java code into generated Java source as is.
<%=expr%> is used to get value of  expression between that tags and put it into resulting HTML page. Usually in Java source it is replaced by out.print(expr);
0
 
LVL 35

Expert Comment

by:TimYates
ID: 11892864
<%  use them

<%= don't (and only put one expression)
0
 
LVL 35

Expert Comment

by:TimYates
ID: 11892879
sorry.. ramazanyich...  I didn't refresh before I posted...

Please ignore my comment LarryAndro

:-)

Tim
0
 
LVL 27

Expert Comment

by:rrz
ID: 11892901
Please look in Tomcat's work folder you will find the translated file that Tomcat produced from your JSP file.  You can see that
<%= test.getMessage() %>   ( this is a JSP scripting element called an JSP expression)
is translated to
out.print(test.getMessage());  

><% test.setMessage("New Message"); %>  ( this is called a scriptlet )
This is just put into the code as is, so it needs  the  ;           rrz

0
 
LVL 27

Expert Comment

by:rrz
ID: 11892996
Thanks for the points Larry.  
Be sure to start looking at the translated file(in work folder) for debugging clues.   rrz
0

Featured Post

Best Practices: Disaster Recovery Testing

Besides backup, any IT division should have a disaster recovery plan. You will find a few tips below relating to the development of such a plan and to what issues one should pay special attention in the course of backup planning.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
jason format for rest webservices and sub resourcing 1 90
Using Tomcat as raspberry pi java app server 13 166
Suggestion on WebSite Template Sites 6 103
web application structure 18 77
This article outlines the process to identify and resolve account lockout in an Active Directory environment.
Knowing where your website is hosted is as important as the features you receive, the monthly fee, and the support you receive. Due diligence should be done when choosing your next hosting provider.
This Micro Tutorial will teach you how to censor certain areas of your screen. The example in this video will show a little boy's face being blurred. This will be demonstrated using Adobe Premiere Pro CS6.
In a recent question (https://www.experts-exchange.com/questions/28997919/Pagination-in-Adobe-Acrobat.html) here at Experts Exchange, a member asked how to add page numbers to a PDF file using Adobe Acrobat XI Pro. This short video Micro Tutorial sh…

809 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question