[FIXED] Can I add <server-mapping> at run time on a tomcat server

Issue

I'm making an API for my web application, which runs on a tomcat server, the plan is to make a CRUD REST API like Prestashop but i don't know how to add the ids of a table to the url path.

So when you go to customers(http://yourUrl.com/api/customers) you will get the reply:

<prestashop xmlns:xlink="http://www.w3.org/1999/xlink">
    <customers>
        <customer id="1" xlink:href="http://yourUrl.com/api/customers/1"/>
        <customer id="2" xlink:href="http://yourUrl.com/api/customers/2"/>
        <customer id="3" xlink:href="http://yourUrl.com/api/customers/3"/>
        <customer id="4" xlink:href="http://yourUrl.com/api/customers/4"/>
        <customer id="5" xlink:href="http://yourUrl.com/api/customers/5"/>
        <customer id="6" xlink:href="http://yourUrl.com/api/customers/6"/>
        <customer id="7" xlink:href="http://yourUrl.com/api/customers/7"/>
        <customer id="8" xlink:href="http://yourUrl.com/api/customers/8"/>
        <customer id="9" xlink:href="http://yourUrl.com/api/customers/9"/>
        <customer id="10" xlink:href="http://yourUrl.com/api/customers/10"/>
        <customer id="11" xlink:href="http://yourUrl.com/api/customers/11"/>
    </customers>
</prestashop>

And then you can go to http://yourUrl.com/api/customers/1 then my plan is to add a servlet with several mappings, I've found out how to ad servlets but not mappings at runtime.

How can i archive this?

Solution

You're on the right track but you don't need to modify the web.xml every time you add a customer. If you need to stay with "pure" servlets then you best bet is to change the mapping in web.xml to something like:

<servlet-mapping>
    <servlet-name>CustomerHandler</servlet-name>
    <url-pattern>/api/customers/*</url-pattern>
</servlet-mapping>

Then, in the servlet (for example, the doGet())

protected void doGet(HttpServletRequest request, HttpServletResponse response) {
  String pathInfo = request.getPathInfo();

  // process pathinfo
}

Your pathInfo String will be whatever comes after the servlet path. So, for example, if the request is "/api/customers/8" then the pathInfo String will be "/8". You'll have to parse this, handling errors (like if the url is "/api/customers/blah"). If the pathInfo is null then there was nothing provided after "/api/customers" and you can assume this returns the list of customers with ids.

But for information, this is the "old" way. It will work but it requires you to do a bit more work than needed. The "new" way is to use JAX-RS. In this case you can define a service to do what you want. The syntax would be something like:

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;


@Path("/api/customers")
public class CustomerProcessor {

    @Path("/")
    @Produces({ MediaType.APPLICATION_XML })
    @GET
    public Response getCustomerData() {
        // get the customer list - assume that it's a String
        String customerXML = ...;

        return Response.ok(customerXML).build();
    }

    @Path("/{customerId}")
    @Produces({ MediaType.TEXT_PLAIN }) # not sure of the return type
    @GET
    public Response getCustomer(@PathParam("customerId") Integer customerId) {
        // customerId is set to what is on the url but you didn't parse it
        Customer customer = getCustomer(customerId);

        return Response.ok(customer).build();
    }
}

Note that you have two methods that are mapped to /api/customers - one with and one without a parameter. This allows you to keep your code separate depending on if you've got a customer id or not.

The biggest issue with the second solution is that Tomcat is not supported "out of the box". You'll need to add JAX-RS support to Tomcat or switch to a server that supports it natively (like TomEE, Wildfly, etc.).

To have Tomcat support JAX-RS, there are other posts on that - it's not terrible but it's not "free" either.

Answered By - stdunbar
Answer Checked By - Mary Flores (JavaFixing Volunteer)