Passing objects from controllers to jsp

Development
1

For the past 24 hours I’ve been trying to pass objects from Java controllers to JSPs and use these objects in JavaScript code but in the JSPs these objects are converted to strings. For example if I have a list of locations passed to the view using

model.put("locations", Context.getLocationService().getAllLocations());

I cannot assign this list of locations to a JavaScript variable. When I do this,

var locations = "${locations}"

All this does is assign a string version of the list of locations which is just concatenated values of Location.getDisplayString(). As a result I can’t use this in JavaScript loops and I can’t even call properties on the objects.

When I do this

var locations = ${locations}

This doesn’t work. It gives a JavaScript error in the browser.

Uncaught SyntaxError: Unexpected identifier

How do I receive objects passed to the model in controllers as objects in views rather than strings?

JSON.parse("${locations}")

doesn’t work either. I get the error

VM2727:1 Uncaught SyntaxError: Unexpected token C in JSON at position 1 at JSON.parse () at HTMLDocument. (patientDashboard.form?patientId=6167&phrase=john:1716) at Function.ready (jquery.min.js?v=1.9.11:26) at HTMLDocument.L

2

Hi @ivange94

Yes, If you assign the variable like that in JS, then it will be converted to a string (actually it doesn’t mean JSON String). And you can’t convert that to JSON since it does not contain the actual JSON format.

So the only way is creating a JSON in the controller and convert to JSON string object, and pass that string object through the JS. Then you can convert that string to JSON in the JS file since it’s an actual JSON string.

So you should try something like this in your controller,

	SimpleObject obj = new SimpleObject();
	for(Location loc : Context.getLocationService().getAllLocations()) {
		SimpleObject locObj = new SimpleObject();
		locObj.put("name", loc.getName());
		locObj.put("uuid", loc.getUuid());
		obj.put("location", locObj);
	}
	model.put("locations", mapper.writeValueAsString(obj));

Then in your JSP assign this stringObject to the JS variable,

var locationsMapping = "${locations}"

So then you can simply get the locationsMapping in your JS file, then you can use the foreach to get each object. if you are using angular then it should be like this following,

angular.forEach(locationsMapping , function(location, key) {
   locName = location.name;
   locUuid = location.uuid;
});

Hope it will help you :slight_smile:

1 Like
3

Thanks @suthagar23. Was headed in that direction with this approach with this

private List<HashMap<Integer, String>> getLocationMaps() {
	List<Location> locations = Context.getLocationService().getAllLocations();
	List<HashMap<Integer, String>> locationMaps = new ArrayList<HashMap<Integer, String>>();
	for (Location location : locations) {
		HashMap<Integer, String> locationMap = new HashMap<Integer, String>();
		locationMap.put(location.getId(), location.getDisplayString());
		locationMaps.add(locationMap);
	}
	return locationMaps;
}

And passing it to view with

Gson gson = new Gson();
	
map.put("locationMaps", gson.toJson(getLocationMaps()));

But I think I like your approach better since I don’t have to use an external library.

4

Yes, we don’t need any external libraries if you used the method which I prefer. We follow this method in other modules also :slight_smile:

5

I just checked and seems SimpleObject is coming from the REST module. That will mean I’d have to declare a dependency to the REST module. That’s not an option for me. The implementation refused to add a new dependency just to make small fix.

6

Why not just fetch the locations via rest instead? Because that already returns the list of locations as json that you can use in javascript.