I'm getting a very strange behaviour in one of my JSP pages. It looks like it doesn't render the complete HTML. It looks like this:
<html>
...
<table>
...
</table>
<div id=
So the last line is exactly what you get when the page is rendered. Furthermore, when you do a view source you get exactly the same. This page doesn't have any fancy logic ... there are no javascript erros, no missing closing tags, etc ...
Is there any sort of page limit for a jsp page?
A bit more background: This page works just fine in a WIN2K server running Tomcat 5.5. I'm upgrading this app to run under a server with WIN2008 + Tomcat 6.0. That's where I get the error ...
Any help is appreciated.
Is there any sort of page limit for a jsp page?
AFAIK, no.
I think that the most likely cause is that your JSP is throwing an exception. Check the Tomcat logs, and look at the JSP at the point after the last HTML that was output.
EDIT
#Adam Crume says: "The exception may be thrown at a point further down from where the output stops, due to buffering."
True. As a temporary hack to get around this, you could surround the JSP's content with a try / finally, and flush the output stream in the finally block.
Is there any sort of page limit for a jsp page?
Yes, there is. It's about 64KB. JSP's are basically compiled into a large try statement. In Java, there's a 64KB limit for try statement. But if you exceed this, it would have prouced a different exception.
This problem at least indicates that you're using scriptlets in the JSP. This is a bad practice. Whenever an exception occurs halfway a JSP page, you'll get a blank or halfbaked page without information about the problem. Don't execute business stuff in JSP, but in a preprocessing Servlet.
Related
In my code I am trying to forward my request by using below line
<jsp:forward page = "<%=request.getContextPath()%>/Welcome.do"/>
However its giving error below
org.apache.jasper.JasperException: /obajsp/OBAHeader.jsp(3,27) JBWEB004214: Error unquoting attribute value
Please someone help me to understand what is issue in my written code?
EDIT:
this was currently working in production without any issue and giving issue in my local IDE
Have you tried using the expression language, rather than a scriptlet?
<jsp:forward page = "${pageContext.request.contextPath}/Welcome.do"/>
<jsp:forward page = "${pageContext.request.contextPath}/Welcome.do"/>
you dont need inline java to get the context path. expressionlanguage is much more comfortable.
I am fairly new in JSP and I am trying to figure out how to pass data entered in the form on a JSP page to the java class and send this data back to the JSP page on click.
My index.jsp looks a bit like this:
<%# page import="mypackage.*" %>
<% myClass c = new myClass();
c.setString("String"); %>
<p>This is a test: <%= c.getString(); %></p>
The above code will output "String". I can access my class with no problems if I set the value on page load. I tried using servlets after some research. I modified my form to add the servlet "testServlet" on form action:
<form method="POST" action="testServlet">
Then on the doPost() method in testServlet I added in this:
String myString = request.getParameter("myString"); //myString is also the name of my textbox
System.out.println("Entered string: " + myString);
However, I am clearly missing a crucial part of the flow of how this should work and I am most probably wrong with this one as well as all the form does after I press submit is redirect to testServlet so I get the error that the resource is not available since it isn't a JSP/html page.
So my questions are, how exactly can I pass data from JSP to java and vice versa? Also, is there a possible way to do this without servlets? And what are good tutorials/examples for studying JSP and its behavior such as passing data? Please help.
After some more research, I am now able to transfer data set on index to detail using jsp:useBean however, as I've read in all the forums I've visited, servlets should be used to handle this but this really confused me more as a beginner so I really want to figure out what I'm missing here.
I've made sure that the servlet is registered on web.xml and I didn't change anything in there.
Update: I've tried re-creating the project from scratch and somehow managed to make the servlet work. As it turns out, I was missing something on the doGet() method. But now my question stands, is there a way to process the form without using servlets or page import in the JSP file? I was shown a sample code that didn't use servlets or page imports. I did take notice at tag.
use the java beans with getters and setters for there class member variables.
i work on JSP and i want to call a java method(Function) on Click on a html button without using<script></script>.how?
i try to write this code:
<button onclick="<%po.killThread();%>">
<font size="4">Kill</font>
</button>
but it doesn't work... so please help me.
thanks
You're misunderstanding how server-side programming works. When you load that page, the webserver will get to the line <button onclick="<%po.killThread();%>"> and will immediately parse and execute the JSP snippet, in your case po.killThread(), and replace everything between the <% and %> with the return value of that method, if any. And all these happens on server side, before client receives any thing. (Note that this will only happen if that page is not already been loaded and compiled into a Servlet by the server.)
Thus, the HTML that client receives, will be something like, <button onclick="some return value or nothing">, which means that nothing will happen when you press the button. If you want to execute further JSP commands on the button press you will need to make a new request to the server - for example, by redirecting the page.
This will call the function killThread when you open the website.
Try to redirect to another jsp which calls the function.
this will not run at all because after the jsp page is compiled it will return the po.killThread() value but will not call this method
You can see this by viewing the page source
JSP is a server-side technology. Did I say server-side?
In order to understand how JSP works and to clear any misconception, JavaRanch Journal (Vol. 4, No. 2): The Secret Life of JavaServer Pages is a very good read.
An excerpt from the same,
JSP is a templating technology best-suited to the delivery of dynamic text documents in a format that is white-space agnostic.
Template text within a JSP page (which is anything that is not a dynamic element), to include all white-space and line terminators, becomes part of the final document.
All dynamic elements in a JSP are interpreted on the server and once the document is sent to the client, no further dynamic interaction is possible (short of requesting the same or another document).
If you are using JSPs, then to perform some method calles, you will have to write a servlet and then call the method in doPost or doGet method of servlet.
On the other hand, if you want to make things simpler, use JSF framework which will help you achieve your objective as JSF supports event handling.
I am trying to refresh the JSP page after certain operations, I am using DWR to be able to use my classes in Javascripts in the JSP files so I have this code:
function removeDN(numplanindex){
DBOps.removeDN(numplanindex);
relaod(true);
}
the above code will break the removeDN() and it would not refresh the page, I have also tried window.location.reload(true) and document.location.reload(true).
I am not sure about the difference as I barely know any Javascript but according to everything on google this should work. I am wondering if anybody know what is wrong with what I am doing wrong.
Thanks
It should be reload(true) instead of relaod(true)
Also see http://www.w3schools.com/jsref/met_loc_reload.asp
I've defined an error-page in my web.xml:
<error-page>
<exception-type>java.lang.Exception</exception-type>
<location>/error.jsp</location>
</error-page>
In that error page, I have a custom tag that I created. The tag handler for this tag e-mails me the stacktrace of whatever error occurred. For the most part this works great.
Where it doesn't work great is if the output has already begun being sent to the client at the time the error occurs. In that case, we get this:
SEVERE: Exception Processing ErrorPage[exceptionType=java.lang.Exception, location=/error.jsp]
java.lang.IllegalStateException
I believe this error happens because we can't redirect a request to the error page after output has already started. The work-around I've used is to increase the buffer size on particularly large JSP pages. But I'm trying to write a generic error handler that I can apply to existing applications, and I'm not sure it's feasible to go through hundreds of JSP pages making sure their buffers are big enough.
Is there a way to still allow my stack trace e-mail code to execute in this case, even if I can't actually display the error page to the client?
The errorPage isn't going to be used if you've already started sending data to the client.
What I do is use a JavaScript callback to check for an incomplete page and then redirect to the error page. At the beginning of your page in an includes header or something, initialize a boolean javascript variable to false, and register an onload handler to check the state and redirect to an error page.
<script type="text/javascript">
var pageLoadSuccessful = false;//set to true in footer.jsp
dojo.addOnLoad(function(){
if (!pageLoadSuccessful) window.location = "<c:url value="/error.do" />";
});
</script>
Then in a footer jsp, be sure to set this variable to true:
<script type="text/javascript">
pageLoadSuccessful = true;//declared in header.jsp
</script>
Have you tried using the <%# page errorPage="/myerrorpage.jsp" %> directive?
You also need to use <% page isErrorPage="true" $> in myerrorpage.jsp, then.
I think that may solve your problem. The only problem with that is that you need to include it in every JSP somehow.
In fact, this particular problem indicates that you were using scriptlets in JSP. This is a bad practice and this particular problem is one of the major reasons for that. You need to move all your business logic to a real java class so that you end up with only taglibs/EL in JSP. In a servlet/filter you can perfectly handle exceptions before forwarding the request to a JSP.