Adding layers dynamically in the ArcGIS Java ADF

There have been many questions about adding layers dynamically in the ADF... And of course the requirement is that the added layer will reflect not only on the map but also on the TOC, layer drop downs, etc...

When working with non-pooled objects, there's a straightforward way of doing this. Look at the source code below:

AGSWebContext agsCtx = ...; //get hold of the AGSWebContext
AGSWebMap agsMap = (AGSWebMap)agsCtx.getWebMap();

//Step 1
agsCtx.applyDescriptions();

//Step 2
MapServer mapso = new MapServer(agsCtx.getServer());
IMap map = mapso.getMap(agsMap.getFocusMapName());
ILayer layer = ...; //create the layer
map.addLayer(layer);

//Step 3
agsCtx.reloadDescriptions();

Let's discuss the 3 steps now:

• Step 1: Before making stateful changes to the object graph (like adding a new layer in this case) you want to apply the current state of the MapDescriptions to the object graph. Calling the applyDescriptions() method on the AGSWebContext does exactly that.


• Step 2: Now that you have the object graph in the current state, you can make the modifications there. In this case we add a new layer to the map.


• Step 3: Once you have made changes to the object graph you want to reload the MapDescriptions to reflect the changed state and additionally, you also want the web controls to display this new state (in this case display the layer on the map control, on the TOC control as well as on any other components working with layers). A single call to the reloadDescriptions() method on the AGSWebContext will do all of this for you.

And that's about it! This sequence of steps holds true for any stateful changes that you want to make to non-pooled objects. The 3-word mantra is APPLY-CHANGE-RELOAD.

If you wanted to work with dynamic layers (or make any stateful changes) in the pooled context, there's indeed more work to do because you are now sharing the server object with others and you want to return the object back to the pool in the same state that you had received it. You need to get access to the server object, apply the current MapDescriptions to the object graph, make the changes to the object graph, reflect the changes in the MapDescriptions and the web controls, undo the changes to the graph and then return the object back to the pool. You can check out the dynamic layers sample on EDN to see this use case in action.