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input value text field in jsp error

My index.jsp is as following:
<form action="FileUploadServlet" id="formSubmit" method="post" enctype="multipart/form-data">
<input type="text" id="txtFileName" value="${fname}"/>
<input type="file" name="fileName" id="selectedFile" style="display: none;">
<input type="button" id="btnBrowse" value="Browse..." onclick="document.getElementById('selectedFile').click();" />
<input type="submit" value="Upload" id="btnUpload">
</form>
with value=${fname} is get from dopost method in servlet when form summited
request.setAttribute("fname", fileName);
getServletContext().getRequestDispatcher("/index.jsp").forward(
request, response);
But it's weird that when I deployed index.jsp
My text field always show ${fname} in text area, even after form submitted, its still get that value (correctly it must show 'filename')
Does anyone meet this problem like me?

First thing is that, you are using wrong syntax to display value in JSP.
Below syntax is wrong.
value="${fname}"
We use expression tag fordisplaying value in JSP page. Expression tag convert into Java statement.
<%=request.getAttribute("fname")%>
When you first time open your index.jsp page, it will show you blank value and when request will come back from server side, then it will show you correct result.
Use below code.
<%if(request.getAttribute("fname")!=null){%>
<input type="text" value ="<%=request.getAttribute("fname") %>"/>
<%}else
{ %>
<input type="text"/>
<%} %>

In JSP, the correct syntax to retrieve the values is
<%=request.getAttribute("fname")%>
This is known as assignment OR expression tag (<%=%>).
Try this ...
<form action="FileUploadServlet" id="formSubmit" method="post" enctype="multipart/form-data">
<input type="text" id="txtFileName" value="<%=request.getAttribute("fname")%>"/>
<input type="file" name="fileName" id="selectedFile" style="display: none;">
<input type="button" id="btnBrowse" value="Browse..." onclick="document.getElementById('selectedFile').click();" />
<input type="submit" value="Upload" id="btnUpload">
</form>
More related to this, here.

Passing Parameters in JSP to Servlet

I have following code
JSP
<tbody>
<c:forEach var="defect" items="${defects}">
<tr>
<td>${defect.name}</td>
<td>${defect.description}</td>
<td>${defect.summary}</td>
<td>${defect.priority}</td>
<td>${defect.originator.name}</td>
<td>${defect.assignee.name}</td>
<td>
<form action="AllOpenDefects?defectId=${defect.id}" method="get">
<input type="submit" value="Update" />
</form>
</td>
</tr>
</c:forEach>
</tbody>
Servlet (in doGet method)
System.out.println((String) request.getParameter("defectId")); // It is printing null
and also in url the defectId is NOT been appended ... Is there any issue with my code?
EDIT: The url is http://localhost:8080/BugManagemetSystem/AllOpenDefects but it should be like http://localhost:8080/BugManagemetSystem/AllOpenDefects?defectId=2

It looks like your browser clears parameters after ?... in action="..." attribute. In that case try passing it via <input type="hidden" .../> like
<form action="AllOpenDefects" method="get">
<input type="hidden" name="defectId" value="${defect.id}"/>
<input type="submit" value="Update" />
</form>
This way form should add them to URL as ?defectId=value of ${defect.id}.

IMHO the short answer to your question is "your code is ok".
As a side note, if it doesn't yield the new required link, it's often an update problem. E.g. try changing the URL algtogether just for testing (form action="Junk"), see if the browser catches it.
If not, try clearing various caches - browser cache, deleting the exploded war and work directories (e.g. in Tomcat it's /webapps/myapp/ and /work)...

On refreshing jsp page got submited again

I have created simple jsp servlet project on that when i submitting jsp form it insert data to specified table but after that when i refersh same jsp form get submitted and same data inserted to table..
ItemUnit.jsp
<form method="POST" action='ItemUnitHandler' name="frmAddUser">
<input type="hidden" name="action" value="insert" />
<table style="width:95%;margin-top:70px;" align="center">
<tr>
<td style="width:10%"> </td>
<td style="width:30%" align="right">Item Unit :</td>
<td style="width:2%"> </td>
<td style="width:40%" align="left"><input type="text" name="itemUnitName" style="width:200px;" /></td>
<td style="width:18%"> </td>
</tr>
<tr><td colspan="5"> </td></tr>
<tr>
<td colspan="5" align="center">
<input type="submit" class="button-2" value="Insert"></input>
<input type="reset" class="button-2" value="Reset"></input>
</td>
</tr>
</table>
</form>
Servlet post method code..
String action = request.getParameter("action");
System.out.println("action :action action : "+action);
if(action == null)
{
redirect = "ItemUnit.jsp";
}
else if(action.equalsIgnoreCase("insert"))
{
ItemUnit objItemUnit = new ItemUnit();
// System.out.println("request.getParameter : "+request.getParameter("itemUnitName"));
objItemUnit.setItemUnit(request.getParameter("itemUnitName"));
dao.addItemUnit(objItemUnit);
redirect = "ItemUnit.jsp";
}
please help me out from this problem...

Ideally, you should land on a static result page, instead of displaying the input form again. The idea is to force the browser to switch to a new URL so that a refresh will not re-trigger another data update. This is the simplest fix.
But if you prefer to use the same screen, you should use a hidden token. You must record some state since you want to differentiate 2 requests from one another: first and second request (the refresh).
Within your logic, plant a token the first time you display the input form. On any incoming request from the same session, check if you have used the token already and use it to determine if this is a second-time request. The diagram below will illustrate it further.
Setup
Processing

How to use session in JSP pages to get information?

I have a JSP page used for editing some user's info. When a user logins to the website, I keep the information in the session, then in my edit page I try the following:
<%! String username=session.getAttribute("username"); %>
<form action="editinfo" method="post">
<table>
<tr>
<td>Username: </td><td> <input type="text" value="<%=username %>" /> </td>
</tr>
</table>
</form>
but it gives error saying session cannot be resolved. What can I do about it?

JSP implicit objects likes session, request etc. are not available inside JSP declaration <%! %> tags.
You could use it directly in your expression as
<td>Username: </td>
<td><input type="text" value="<%= session.getAttribute("username") %>" /></td>
On other note, using scriptlets in JSP has been long deprecated. Use of EL (expression language) and JSTL tags is highly recommended. For example, here you could use EL as
<td>Username: </td>
<td><input type="text" value="${username}" /></td>
The best part is that scope resolution is done automatically. So, here username could come from page, or request, or session, or application scopes in that order. If for a particular instance you need to override this because of a name collision you can explicitly specify the scope as
<td><input type="text" value="${requestScope.username}" /></td> or,
<td><input type="text" value="${sessionScope.username}" /></td> or,
<td><input type="text" value="${applicationScope.username}" /></td>

Use
<% String username = (String)request.getSession().getAttribute(...); %>
Note that your use of <%! ... %> is translated to class-level, but request is only available in the service() method of the translated servlet.
See how JSP code is translated to a servlet.

The reason why you are getting the compilation error is, you are trying to access the session in declaration block (<%! %>) where it is not available. All the implicit objects of jsp are available in service method only. Code of declarative blocks goes outside the service method.
I'd advice you to use EL. It is a simplified approach.
${sessionScope.username} would give you the desired output.

Suppose you want to use, say ID in any other webpage then you can do it by following code snippet :
String id=(String)session.getAttribute("uid");
Here uid is the attribute in which you have stored the ID earlier. You can set it by:
session.setAttribute("uid",id);

<%! String username=(String)session.getAttribute("username"); %>
form action="editinfo" method="post">
<table>
<tr>
<td>Username: </td><td> <input type="text" value="<%=username %>" /> </td>
</tr>
</table>
add <%! String username=(String)session.getAttribute("username"); %>

You can directly use (String)session.getAttribute("username"); inside scriptlet tag ie <% %>.

form action="editinfo" method="post">
<table>
<tr>
<td>Username:</td>
<td>
<input type="text" value="<%if( request.getSession().getAttribute(" parameter_whatever_you_passed ") != null
{
request.getSession().getAttribute("parameter_whatever_you_passed ").toString();
}
%>" />
</td>
</tr>
</table>
</form>

How do I submit the right value?

<c:forEach items="${movieList}" var="movie" varStatus="status">
<tr class="<c:if test="${status.count % 2 == 0}">even</c:if>">
<td>${movie.title}</td>
<td>${movie.genre}</td>
<td>${movie.year}</td>
<td>${movie.boxoffice}</td>
<td>
<form:form action=edit.htm>
<input type="hidden" name="edit" value="movie name">
<input type="submit" value="Edit">
</form:form>
<form:form action=delete.htm>
<input type="hidden" name="delete" value="movie name">
<input type="submit" value="Edit">
</form:form>
</tr>
</c:forEach>
This is the section of code I have at the moment. The idea is to display movie data, but also provide buttons to send the user to either a filled form page to edit the data or simply delete the respective data and redirect to the same page. I am just unsure as how to pass along the movie object. I know it is simple, but I can't find the reference I used previously...
Thanks.

U can try this :
put this object in a hidden input
<input type="hidden" id="hidden_object" value="" name="hidden_object"></input>
than you can access the value with the method getParameter()
OR
put this object in your session
in your jsp
<% session.setAttribute("movie", ${movie}); %>
good luck