url-pattern in web.xml not recognising multiple url

Question

I have web.xml like this :

  <servlet>
    <servlet-name>MyDisplayCourse</servlet-name>
    <servlet-class>edu.itn.controller.MyDisplayCourse</servlet-class>
</servlet>

and servlet-mapping for the servlet is:

 <servlet-mapping>
    <servlet-name>MyDisplayCourse</servlet-name>
     <url-pattern>/admin/displaystudent</url-pattern>    
    <url-pattern>/displaystudent</url-pattern>    
 </servlet-mapping>

When i use :

 <url-pattern>/displaystudent</url-pattern>   

It finds the servlet MyDisplayCourse, but when i use append /admin/

 <url-pattern>/admin/displaystudent</url-pattern> 

This shows 404 error code in my web app. Can someone help me why doesn't support url like /admin/displaystudent but supports only single url like /displaystudent only.

Answer 1

There is no issue with url-pattern

the issue is with your code in DisplayStudent.java

replace

RequestDispatcher rd=request.getRequestDispatcher("StudentTable.jsp");

with

RequestDispatcher rd=request.getRequestDispatcher("/StudentTable.jsp");

ServletRequestSpec

If the path begins with a "/" it is interpreted as relative to the current context root

otherwise it will concatinate with relative path in your case '/admin/StudentTable.jsp'

following code is implementation of getRequestDispatcher

@Override
public RequestDispatcher getRequestDispatcher(final String path) {
String realPath;
 if (path.startsWith("/")) {
    realPath = path;
 } else {
    String current = exchange.getRelativePath();
    int lastSlash = current.lastIndexOf("/");
    if (lastSlash != -1) {
        current = current.substring(0, lastSlash + 1);
    }
    realPath = CanonicalPathUtils.canonicalize(current + path);
 }
 return new RequestDispatcherImpl(realPath, servletContext);
}