Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
?
Solved

JSP Call to Bean Getter Malfunction

Posted on 2004-08-25
9
Medium Priority
?
345 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
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 2
  • 2
  • +1
9 Comments
 
LVL 19

Accepted Solution

by:
ramazanyich earned 920 total points
ID: 11892445
Use <%=test.getMessage()%>
0
 
LVL 28

Assisted Solution

by:rrz
rrz earned 80 total points
ID: 11892492
><% test.getMessage(); %>
Please use  instead
<%=test.getMessage()%>    rrz
0
 
LVL 28

Expert Comment

by:rrz
ID: 11892503
Sorry ramazanyich I didn't see your post.
0
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
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 920 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 28

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 28

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

[Webinar] Lessons on Recovering from Petya

Skyport is working hard to help customers recover from recent attacks, like the Petya worm. This work has brought to light some important lessons. New malware attacks like this can take down your entire environment. Learn from others mistakes on how to prevent Petya like worms.

Question has a verified solution.

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

This month, Experts Exchange sat down with resident SQL expert, Jim Horn, for an in-depth look into the makings of a successful career in SQL.
Tech spooks aren't just for those who are tech savvy, it also happens to those of us running a business. Check out the top tech spooks for business owners.
Have you created a query with information for a calendar? ... and then, abra-cadabra, the calendar is done?! I am going to show you how to make that happen. Visualize your data!  ... really see it To use the code to create a calendar from a q…
In response to a need for security and privacy, and to continue fostering an environment members can turn to for support, solutions, and education, Experts Exchange has created anonymous question capabilities. This new feature is available to our Pr…

596 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