Why can't I redirect correctly my Java Servlet? [duplicate] - servlets

Question

Does servlet support urls as follows:
/xyz/{value}/test
where value could be replaced by text or number.
How to map that in the web.xml?

Answer 1

It's not supported by Servlet API to have the URL pattern wildcard * in middle of the mapping. It only allows the wildcard * in the end of the mapping like so /prefix/* or in the start of the mapping like so *.suffix.
With the standard allowed URL pattern syntax your best bet is to map it on /xyz/* and extract the path information using HttpServletRequest#getPathInfo().
So, given an <url-pattern>/xyz/*</url-pattern>, here's a basic kickoff example how to extract the path information, null checks and array index out of bounds checks omitted:
String pathInfo = request.getPathInfo(); // /{value}/test
String[] pathParts = pathInfo.split("/");
String part1 = pathParts[1]; // {value}
String part2 = pathParts[2]; // test
// ...
If you want more finer grained control like as possible with Apache HTTPD's mod_rewrite, then you could look at Tuckey's URL rewrite filter or homegrow your own URL rewrite filter.

Answer 2

As others have indicated, the servlet specification does not allow such patterns; however, you might consider JAX-RS which does allow such patterns, if this is appropriate for your use case.
#Path("/xyz/{value}/test")
public class User {
public String doSomething(#PathParam("value") final String value) { ... }
}
Or:
#Path("/xyz/{value}")
public class User {
#Path("test")
public String doTest(#PathParam("value") final String value) { ... }
}
(Related to: https://stackoverflow.com/a/8303767/843093.)

Answer 3

It does support mapping that url; but doesn't offer any validation.
In your web xml, you could do this....
/xyz/*
But that won't guarantee that the trailing test is present and that it is the last item. If you're looking for something more sophisticated, you should try urlrewritefilter.
http://code.google.com/p/urlrewritefilter/

Answer 4

You shouldn't be doing that in web.xml rather you can point every request to your filter (Patternfilter) and can check for URL
package com.inventwheel.filter;
import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
/**
* Servlet Filter implementation class PatternFilter
*/
#WebFilter("/*")
public class PatternFilter implements Filter {
/**
* Default constructor.
*/
public PatternFilter() {
// TODO Auto-generated constructor stub
}
/**
* #see Filter#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
}
/**
* #see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
*/
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
String servletPath = ((HttpServletRequest)request).getServletPath();
String requestURI = ((HttpServletRequest)request).getRequestURI();
Pattern pattern = Pattern.compile(".*"+servletPath+"/(.*)");
Matcher matcher = pattern.matcher(requestURI);
if (matcher.matches())
{
String param = matcher.group(1);
// do stuff with param here..
}
chain.doFilter(request, response);
}
/**
* #see Filter#init(FilterConfig)
*/
public void init(FilterConfig fConfig) throws ServletException {
// TODO Auto-generated method stub
}
}

Answer 5

As stated above, base servlets does not support patterns like you specified in your question. Spring MVC does support patterns. Here is a link to the pertinent section in the Spring Reference Document.

Answer 6

No Servlet doesn't support patterns like that, possible approach as mentioned by other folks as well is to use /* after xyz but that doesn't check for {value} or /test. Better you go for Spring or JAX-RS. However if you plan to stick with Servlet a better way to write it:
#WebServlet(urlPatterns = {"/xyz/*"})

Answer 7

An answer from the year 2022.
Servlets do still not allow wildcards, so we can't do things like:
/xyz/{value}/test
Paul Tuckeys urlrewritefilter is still in version 4.0.3, and not compatible with the new jakarta namespace [1] (Version 5 is in development).
I found a solution in Tomcat itself, with its feature RewriteValve.
See https://rmannibucau.metawerx.net/post/tomcat-rewrite-url for a step-by-step manual. This is a convenient solution for allowing wildcards in the middle of a URL.
[1] https://github.com/paultuckey/urlrewritefilter/issues/239