passing parameter from jsp to servlet through url pattern of servlet

Question

I got a requirement to send one parameter through url pattern of servlet (like we send through <a href="example.jsp?id=1">send</a> ) in the same way I need it through url pattern.

I do this with other possibilities like

1. I can send that parameter as hidden type
2. i can put in a request and session objects

these methods are working fine no problem

but through url it's not taking? I want to know whether it is possible or not?

the code I have tried

jsp page

<a href="download?filename=<%=filename%>" target="_blank"> <font color="black"><%=filename%> </font></a>

servlet code

 String  filename=request.getParameter("filename");

and i need one answer can we pass parameter through url pattern if yes how? ie like same as through <a href="example?id=1">send</a> or differently?

Answer 1

I am just trying to give you an example

.jsp FILE

<% String filename ="nameofFile.txt"; %>
<a href="download?filename=<%= filename %>" ></a>

SERVLET CODE

String filename = (String)request.getParameter("filename");
BufferedReader fir= new BufferedReader(new FileReader(new FileInputStream(filename))); 
PrintWriter out = response.getWriter();
while(fir.ready())
out.println(fir.readLine())

I think you are getting blank page because you are not sending any response back to the client, here out.println will actually send response back to the client

Answer 2

Always encode the URL. In JSP try with <c:url> JSTL Tag.

For example

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
...
<a href='<c:url value="/jsp/index.htm"/>'>TEST</a>

Read more..

Note: Use JSTL and EL instead of Scriplets.

Answer 3

It is possible but it looks like your browser clears parameters after ?... in action="..." attribute. In that case try passing it via <input type="hidden" .../> like

<form action="sendFileToServlet" method="get">
    <input type="hidden" name="filename" value="<%=filename%>"/>
    <input type="submit" value="Send" />
</form> 

This way form should add them to URL as ?filename= value of <%=filename%> .

Answer 4

Yes you can send as like trough jsp.

i just tested now it's working fine the blank page is coming because of other statements written in your servlet code so make sure servlet code is correct.