如何以编程方式更新Appengine数据存储区中的数据？

Question

I just started to use appengine datastore and looking for a way to update the data while fetching it. Here is the code:

DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
Query q = new Query("Users").addFilter("value", Query.FilterOperator.EQUAL, 1);
PreparedQuery pq = datastore.prepare(q);
    if(pq!=null) {

        for (com.google.appengine.api.datastore.Entity result : pq.asIterable()) {
            nodeID = result.getProperty("nodeId").toString();
            result.setProperty("value",0);
            datastore.put(result);
            break;

        }
    }

It's fetching the data but not able to update the value field in datastore . What I am doing wrong here?

Answer 1

I tried your above code and it worked fine for me.

DatastoreService datastore =  DatastoreServiceFactory.getDatastoreService();
Query q = new Query("Users").addFilter("value", Query.FilterOperator.EQUAL, 1);
PreparedQuery pq = datastore.prepare(q);
if(pq!=null) {

    for (com.google.appengine.api.datastore.Entity result : pq.asIterable()) {
        nodeID = result.getProperty("nodeId").toString();
        result.setProperty("value",0);
        datastore.put(result);
        break;

    }
}