Minimal example of a 4-verb REST service in IBM Domino XPages, with no external dependencies.

REST.xsp

<?xml version="1.0" encoding="UTF-8"?>
<!-- XPages source for REST service. -->
<xp:view xmlns:xp="http://www.ibm.com/xsp/core" rendered="false">
  <xp:this.afterRenderResponse><![CDATA[#{javascript:
com.ath0.xrest.Service.dispatch();
}]]></xp:this.afterRenderResponse>
</xp:view>

Service.java

/**
 * Copyright 2013 IBM Corporation.
 * Distributed under the terms of the Apache License, Version 2.0.
 * http://www.apache.org/licenses/LICENSE-2.0.
 */

package com.ath0.xrest;

import java.io.BufferedReader;
import java.io.IOException;
import java.util.Map;
import java.util.Map.Entry;

import javax.faces.context.ExternalContext;
import javax.faces.context.FacesContext;
import javax.faces.context.ResponseWriter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Example code showing a minimal implementation of a REST service for 
 * IBM Domino XPages.
 * 
 * Note that URL parameters in params are still processed by the XPages 
 * runtime, and not the raw servlet runtime. This leads to some limitations 
 * on allowed syntax, and means you can end up with parameters like 
 * 'OpenXPage' in the map.
 * 
 * @author meta@pobox.com
 */
public class Service {

  // These are the standard external contexts you would access in 
  // server-side JavaScript.
  private static FacesContext faccon;
  private static ExternalContext extcon;
  private static HttpServletRequest request;
  private static HttpServletResponse response;
  // This holds web form HTTP POST parameters, if there are any.
  private static Map<String, String[]> params;

  // HTTP requires that lines be terminated with CRLF, even if the server 
  // is Linux, so I use this to end lines instead of writeln.
  private static final String CRLF = "\r\n";

  // The MIME type used for form data.
  private static final String FORM_DATA = "application/x-www-form-urlencoded";
  private static final String HTTP_POST = "POST";
  private static final String HTTP_GET = "GET";
  private static final String HTTP_PUT = "PUT";
  private static final String HTTP_DELETE = "DELETE";

  public Service() {
    faccon = FacesContext.getCurrentInstance();
    extcon = faccon.getExternalContext();
    request = (HttpServletRequest) extcon.getRequest();
    response = (HttpServletResponse) extcon.getResponse();
  }

  @SuppressWarnings("unchecked")
  public void run() {
    String ctype = request.getContentType();
    String method = request.getMethod();

    try {
      if (HTTP_POST.equalsIgnoreCase(method) && FORM_DATA.equalsIgnoreCase(ctype)) {
        params = request.getParameterMap();
        this.post();
      } else if (HTTP_POST.equalsIgnoreCase(method)) {
        this.post();
      } else if (HTTP_GET.equalsIgnoreCase(method)) {
        this.get();
      } else if (HTTP_PUT.equalsIgnoreCase(method)) {
        this.put();
      } else if (HTTP_DELETE.equalsIgnoreCase(method)) {
        this.delete();
      }
    } catch (Exception ex) {
      try {
        faccon.getResponseWriter().write(ex.getMessage());
      } catch (IOException ioe) {
        // Not much we can do
      }
      response.setStatus(501);
    }
  }

  /**
   * Override or alter this to implement your GET operation.
   * @throws IOException
   */
  public void get() throws IOException {
    dump();
  }

  /**
   * Override or alter this to implement your GET operation.
   * @throws IOException
   */
  public void post() throws IOException {
    dump();
  }

  /**
   * Override or alter this to implement your GET operation.
   * @throws IOException
   */
  public void put() throws IOException {
    dump();
  }

  /**
   * Override or alter this to implement your GET operation.
   * @throws IOException
   */
  public void delete() throws IOException {
    dump();
  }

  /**
   * Sample code which dumps out the REST request received.
   * @throws IOException
   */
  static public void dump() throws IOException {
    response.setContentType("text/plain");
    response.setHeader("Cache-Control", "no-cache");
    response.setCharacterEncoding("utf-8");
    response.setStatus(200); // HTTP OK

    ResponseWriter writer = faccon.getResponseWriter();
    writer.write("Received HTTP " + request.getMethod() + "." + CRLF);

    writer.write("Request content-type = " + request.getContentType() + CRLF);
    writer.flush();
    BufferedReader r = null;
    try {
      r = request.getReader();
      if (r.ready()) {
        String line = r.readLine();
        writer.write("First line of body data:");
        writer.write(line);
        writer.write(CRLF);
      }
    } catch (Exception e) {
      writer.write("No body data readable: " + e.getMessage() + "." + CRLF);
    } finally {
      if (r != null) {
        r.close();
      }
    }

    if (params != null) {
      for (Entry<String, String[]> parm: params.entrySet()) {
        writer.write("POST parameter ");
        writer.write(parm.getKey());
        writer.write(" = ");
        writer.write(parm.getValue()[0]);
        writer.write(CRLF);
      }
    } else {
      writer.write("Parameter map was null." + CRLF);
    }

    // Here's how you end your output:
    writer.endDocument();
    faccon.responseComplete();
  }

  public static final void dispatch() {
    Service me = new Service();
    me.run();
  }
}