After a couple of hours of presentations and brainstorming  we started hacking.  I teamed up with  skakanka to experiment with sending the contents of a wave to a Proof of concept Document storage system . But we ended up doing a simple Echo Bot (but hey! we illustrated how to extract content from a wavelet and send it somewhere).

I brought a mac and used the Google eclipse plugin for galileo for coding. It helped that I allready had a Google app engine account from some earlier experiments – but I spent some time learning the different key combinations on the mac – it was great fun though (and now I know how to use eclipse on  a mac!). Deploying on google app engine is as simple as pressing a button in eclipse (I also tried using som ant tasks in my earlier experiments).

We managed to have a google wave running sometime before lunch – so it is very easy to get a basic understanding what a wave bot is all about. (You could think of it as an ircbot on steroids ! )

The overall idea of building a google wave bot is to listen to incoming events defined in the protocol. Let’s say we want to perform something when somebody enters the wave or write something – then we can define the capabilities like this:




0.0.4







Then the robot should act on the defined events in a manner similar to this :


@Override
public void processEvents(RobotMessageBundle robotMessageBundle) {
Wavelet wavelet = robotMessageBundle.getWavelet();
String rootText = wavelet.getRootBlip().getDocument().getText();
for ( Event e: robotMessageBundle.getEvents()){
Blip b= e.getBlip();
String text= e.getBlip().getDocument().getText();
if (e.getType().equals(EventType.BLIP_SUBMITTED)){
e.getBlip().getDocument().append( makeEcho(text));
}
}
}


The Wave client api offers something like the DOM api for the xml being sent back and forth. During the hackathon I learnt that there is no way to ask for the contents of the entire wave from a single blip – so it will require some thinking to save the entire contents of the wave – but it should be doable.

Sometime during the afternoon things started to slow down on the wave test server. I noticed that some of the other guys doing a multiuser interactive drawing gadget for wave. It looked like they recorded a delta to send every time the mouse moved! This made me want to look a bit under “the hood”:

Sounds like the team are handling the multiuser issues using “operational transforms” . Maybe they could somehow ‘batch’ deltas from interactive gadgets ? I have yet to fully understand how “operational transforms” work  – but it sounds like an exciting challenge to make this work on a large scale!

Da det iøjeblikket er for webapplikationer jeg undersøger , så har jeg valgt at køre under tomcat5.5 på min testmaskine.
tomcat5.5 og groovy kan nemt installeres sammen på ubuntu. Det gøres sådan her (jeg antager at du allerede har installeret mysql og den virker)


sudo apt-get install tomcat5.5 tomcat5.5-admin groovy


For at få tomcat5.5 til at køre groovy til demonstrationsformål har jeg sat “TOMCAT5_SECURITY=no” i filen “/etc/init.d/tomcat5.5″. I et produktionsmiljø bør man gøre sig overvejelser om brugen af classloaders.

Jeg har til demonstrationsformål valgt at rette filen /etc/tomcat5.5/tomcat-users.xml til således at bruger “tomcat” har roles=”tomcat,admin,manager” – derved kan jeg logge ind i  /manager/ vha ‘tomcat’ og ‘tomcat’ .Bemærk at der nederst på manager-siden står “WAR file to deploy”. Her kan du uploade flg. fil : groovytest.war

Herefter kan der ses et resultat i  /groovytest/ på testmaskinen. groovy testkoden ser således ud:


Sql.loadDriver("com.mysql.jdbc.Driver");
sql = Sql.newInstance("jdbc:mysql://localhost:3306/test", "web","sockmonkey");

sql.eachRow("select * from test") {
println it.id + " " + it.name
}
print "mere test"


“test.groovy”  henviser til en database “test” med tabellen “test”. Disse kan skabes vha filen “test.sql” der er vedlagt i groovytest.war

war-filen indeholder mysql-driveren , så forbindelsen mellem mysql og groovy skulle fungere der. Men hvis du vil forsøge dig med at køre test.groovy fra kommandolinjen , så kan du også det , hvis du kopierer mysql-connector-java-3.1.14-bin.jar over i din ~/.groovy/lib/ . På den facon kan du afvikle testen på serveren uden om tomcat.

Hvis vi antager flg klasser :


class A{
public int B;
public int C;
public D F;
public D G;
};

class D {
public String E;
}


og at de var initialiseret således:

A a=new A();
a.B=1;
a.C=2;
a.F=new D();
a.F.E="test";
a.G=new D();
a.G.E="test2";


Så kunne man kigge på selve java objekterne vha reflection for at generere JSON output til bruge i javascript således:


public class JsonEmit{
public static String emit(Object target) throws Exception{
StringBuilder sb=new StringBuilder();
sb.append("{");
Class targetClass=target.getClass();
Field[] publicFields = targetClass.getFields();
for (int i=0;i String sFieldName = publicFields[i].getName();
Class typeClass = publicFields[i].getType();
String sFieldType = typeClass.getName();
Object value = publicFields[i].get(target);
if(value!=null){
sb.append(sFieldName+":");
if(typeClass.isPrimitive()
||sFieldType=="java.lang.String"){
sb.append("""+value.toString()+""");
}else{
sb.append(JsonEmit.emit(value));
}
}
if(i!=(publicFields.length-1))
sb.append(",");
}
sb.append("}");
return(sb.toString());
}


På den facon vil man kunne genere JSON ved et simpelt kald til

JsonEmit.emit(a)


hvorefter man vil se

{B:"1",C:"2",F:{E:"test"},G:{E:"test2"}}