How can I use a servlet filter to change an incoming servlet request url from
http://nm-java.appspot.com/Check_License/Dir_My_App/Dir_ABC/My_Obj_123
to
http://nm-java.appspot.com/Check_License?Contact_Id=My_Obj_123
?
Update: according to BalusC's steps below, I came up with the following code:
public class UrlRewriteFilter implements Filter {
@Override
public void init(FilterConfig config) throws ServletException {
//
}
@Override
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws ServletException, IOException {
HttpServletRequest request = (HttpServletRequest) req;
String requestURI = request.getRequestURI();
if (requestURI.startsWith("/Check_License/Dir_My_App/")) {
String toReplace = requestURI.substring(requestURI.indexOf("/Dir_My_App"), requestURI.lastIndexOf("/") + 1);
String newURI = requestURI.replace(toReplace, "?Contact_Id=");
req.getRequestDispatcher(newURI).forward(req, res);
} else {
chain.doFilter(req, res);
}
}
@Override
public void destroy() {
//
}
}
The relevant entry in web.xml
look like this:
<filter>
<filter-name>urlRewriteFilter</filter-name>
<filter-class>com.example.UrlRewriteFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>urlRewriteFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
I tried both server-side and client-side redirect with the expected results. It worked, thanks BalusC!
javax.servlet.Filter
.doFilter()
method, cast the incoming ServletRequest
to HttpServletRequest
.HttpServletRequest#getRequestURI()
to grab the path.java.lang.String
methods like substring()
, split()
, concat()
and so on to extract the part of interest and compose the new path.ServletRequest#getRequestDispatcher()
and then RequestDispatcher#forward()
to forward the request/response to the new URL (server-side redirect, not reflected in browser address bar), or cast the incoming ServletResponse
to HttpServletResponse
and then HttpServletResponse#sendRedirect()
to redirect the response to the new URL (client side redirect, reflected in browser address bar).web.xml
on an url-pattern
of /*
or /Check_License/*
, depending on the context path, or if you're on Servlet 3.0 already, use the @WebFilter
annotation for that instead.Don't forget to add a check in the code if the URL needs to be changed and if not, then just call FilterChain#doFilter()
, else it will call itself in an infinite loop.
Alternatively you can also just use an existing 3rd party API to do all the work for you, such as Tuckey's UrlRewriteFilter which can be configured the way as you would do with Apache's mod_rewrite
.