Sample code to retrieve multilevel results using the MMBase remote interface

[Ignacio Renuncio]

Hi everybody again,

This time I'm sending some sample code to retrieve ClusterNodes composed of
various fields from two different nodemanagers.

I was reading a ton of docs, including the "SearchQuery introduction"
document but it seems to be a bit outdated. Sniffing here and there, in the
document and through the apidocs, I came up with the following solution.

Could anybody take a quick look to it?
Does it follow the "best practices" for MMBase?


    // Connection parameters for the remote cloud
    CloudContext cloudContext =
ContextProvider.getCloudContext("rmi://127.0.0.1:1111/remotecontext");
    HashMap credenciales = new HashMap();
    credentials.put("username", "admin");
    credentials.put("password", "admin2k");

    // We connect to the cloud
    Cloud cloud = cloudContext.getCloud("mmbase", "name/password",
credentials);

    // Create the query to retrieve elements from the CMS repository
    NodeQuery query = cloud.createNodeQuery();

    // Define the object types involved in the query
    NodeManager url = cloud.getNodeManager("url");
    NodeManager tema = cloud.getNodeManager("tema");

    // Create the steps for the query, normal steps (Step) for the usual
object types,
    // special steps (RelationStep.getNext) to add related object types
through insrel.
    Step source1 = query.addStep(url);
    Step source2 = query.addRelationStep(tema).getNext();

    // We add the desired fields from any of the sources
    StepField campo_number = query.addField(source1,
url.getField("number"));
    query.addField(source1, url.getField("nombre"));
    query.addField(source1, url.getField("url"));
    query.addField(source2, tema.getField("descripcion"));

    // Set the order criteria
    query.addSortOrder(campo_number, SortOrder.ORDER_DESCENDING);

    // Define the max number of nodes to retrieve (never all of them since
it's a remote interface)
    query.setMaxNumber(10);

    // Execute the query against the CMS cloud
    List listaElementos = cloud.getList(query);
    Iterator iteradorElementos = listaElementos.iterator();
    while(iteradorElementos.hasNext()) {
        // For each element...
        Node element = (Node) iteradorElementos.next();
        System.out.println("(Node): " + element + "\n");
        System.out.println("url: " + element.getStringValue("url.url"));
        System.out.println("descripcion: " +
element.getStringValue("url.descripcion"));
        System.out.println("nombre: " +
element.getStringValue("url.nombre"));
        System.out.println("tema: " +
element.getStringValue("tema.descripcion"));
    }


I started creating the NodeQuery this way:    NodeQuery query =
cloud.getNodeManager("url").createNodeQuery();

But soon I saw the query was tied to a given NodeManager.


After that, I changed it to:    NodeQuery query = cloud.createNodeQuery();

And added different fields from different sources. At first sight I thought
it couldn't work because I was not using ClusterNodes at all, so I printed
each 'element.getNodeManager()' to see which NodeManager was assigned to
that mix of fields from different sources.

What I got was: 'virtualnodes_1091717316612', a really clever answer!!


---

So, if I'm already getting multilevel info, should I use ClusterNodes?

Is this code the preferred method to do this kind of operation?


Thanks in advance,


Ignacio Renuncio.-