capabilities.xml

<?xml version="1.0" encoding="utf-8"?>
<w:robot xmlns:w="http://wave.google.com/extensions/robots/1.0">
        <w:capabilities>
                <w:capability name="WAVELET_PARTICIPANTS_CHANGED"
                        content="true" />
                <w:capability name="BLIP_SUBMITTED" content="true" />
        </w:capabilities>
        <w:version>3</w:version>
</w:robot>

WaveRobot1Servlet.java

package de.kopis.wave.robot;

import java.util.logging.Logger;

import com.google.wave.api.AbstractRobotServlet;
import com.google.wave.api.Blip;
import com.google.wave.api.Event;
import com.google.wave.api.RobotMessageBundle;
import com.google.wave.api.TextView;
import com.google.wave.api.Wavelet;

@SuppressWarnings("serial")
public class WaveRobot1Servlet extends AbstractRobotServlet {
        private static final Logger LOG = Logger.getLogger(WaveRobot1Servlet.class
                        .getName());

        @Override
        public void processEvents(final RobotMessageBundle bundle) {
                Wavelet wavelet = bundle.getWavelet();
                LOG.info("Receiving events.");

                if (bundle.wasSelfAdded()) {
                        LOG.info("Adding myself to wave.");
                        final Blip blip = wavelet.appendBlip();
                        reply(blip, "Here I am.");
                }

                for (Event e : bundle.getBlipSubmittedEvents()) {
                        LOG.info("A blip was submitted. Reversing it and replying.");
                        Blip blip = e.getBlip();
                        replyWithReversedText(blip);
                }
        }

        private void replyWithReversedText(final Blip blip) {
                TextView textView = blip.getDocument();
                StringBuffer text = new StringBuffer(textView.getText());
                reply(blip, text.reverse().toString());
        }

        private void reply(final Blip blip, final String text) {
                if (text.length() > 0) {
                        Blip newBlip = blip.createChild();
                        TextView newTextView = newBlip.getDocument();
                        newTextView.append(text);
                }
        }
}

web.xml

<?xml version="1.0" encoding="utf-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
        <servlet>
                <servlet-name>WaveRobot1</servlet-name>
                <servlet-class>de.kopis.wave.robot.WaveRobot1Servlet</servlet-class>
        </servlet>
        <servlet-mapping>
                <servlet-name>WaveRobot1</servlet-name>
                <url-pattern>/_wave/robot/jsonrpc</url-pattern>
        </servlet-mapping>
</web-app>