fetchEntityByKey not making any requests to the server - breeze

Question

I'm trying to create a filemanager using Angularjs and I recently discovered Breezejs and was interested in trying to use it to communicate with my backend and manage my model relations. The backend is a rest api over which I have full control.
I am however running into a problem. I know the id of the file, so I would like to make a request to url of the form backend_url/files/:fileId where :fileId is the url of the file base64 encoded. According to the documentation I should use EntityManager.fetchEntityByKey() for this purpose. This is the function that i use to create the Angularjs service:
var FilestoreService = function () {
var dataService, manager;
dataService = new breeze.DataService({
serviceName: "../VFS-Symfony-Backend/web/app_dev.php/filesystems/local/",
hasServerMetadata: false
});
manager = new breeze.EntityManager({
dataService: dataService
});
manager.metadataStore.addEntityType(fileEntityType);
return {
findOneById: function (id) {
/* I have tried to leave the 3th argument empty or changing it to false with the same results */
return manager.fetchEntityByKey("File", id, true).then(function(){console.log("success");}).fail(function(){console.log("failure");});
/* I have also tried the following approach with the same result:
var type, key, query;
type = manager.metadataStore.getEntityType("File");
key = new breeze.EntityKey(type, id);
query = breeze.EntityQuery.fromEntityKey(key);
return manager.executeQuery(query);
*/
}
};
};
where fileEntityType is defined as:
var FileEntityType = new breeze.EntityType({
shortName: "File"
});
FileEntityType.addProperty(new breeze.DataProperty({
name: "uri",
dataType: breeze.DataType.String,
isNullable: false
}));
FileEntityType.addProperty(new breeze.DataProperty({
name: "mTime",
dataType: breeze.DataType.Int16,
isNullable: false
}));
FileEntityType.addProperty(new breeze.DataProperty({
name: "type",
dataType: breeze.DataType.String,
isNullable: false
}));
FileEntityType.addProperty(new breeze.DataProperty({
name: "size",
dataType: breeze.DataType.int16,
isNullable: true
}));
However, when I call findOneById no request is made to the server and 2 lines are logged to the console:
Should be empty:[] by q.js
failure (as per the fail() callback function)
A 'normal' query (manager.executeQuery(new breeze.EntityQuery().from("Files"));) does result in a request to the server as expected.
I am really quite lost here. I have searched for a solution all weekend and finaly decided to post on SO hoping someone might be able to help me.
Thanks very much for reading.

Answer 1

At least one problem is that you haven't identified the key ('id'?) in your metadata description of the "File" entity type. You have defined every other property except the 'id' property.
You know this but let me tell other readers of this question who may not understand that you are defining the metadata on the JS client rather than retrieving it from the server.
I'm also curious why you are using int16? Is that really the right type? Do you really need to shave off the two bytes?
Finally, Breeze's fetchEntityByKey won't make a request URL in the form "backend_url/files /:fileId". Instead, the request URL will be "backend_url/files /?id=:fileId" as befits an OData query. See the network traffic for Id queries in the queryTests.cs of the DocCode sample.
You can still get that file if the server expects the URL you specified. You won't be using the Breeze query syntax. You'll just hit the service with the URL it expects, e.g.,
function findOne(id) {
// check cache first
var file = manager.getEntityByKey('File', id);
if (file) {
console.log("got it from cache");
return Q(file); // got it; return in resolved promise
}
// not in cache; get from server
return breeze.EntityQuery
.from('Files/'+id) // constructs the URL you want
.using(manager).execute()
.then(function(data){
console.log("success");}
// return the file in a resolved promise
return data.results[0] || null;
})
.fail(function(error){
console.log("failure: "+ error.message);
});
}
This is a variation on the getByIdCacheOrRemote method in queryTest.cs in the DocCode sample.
Yes, it's longer. You're reimplementing fetchEntityByKey so you can hit the remote service the way it expects.
The method begins by looking for the file in cache. The getEntityByKey is a synchronous search of the cache. The findOne method has async syntax ... returns a promise ... because it might have to go to the server. So if we find the file in cache (synchronously), we wrap the result in a resolved Q.js promise for the benefit of the caller which is expecting findOne to be asynchronous.
If the file is not found in cache, you go to the server with a "query" that is really just a request on the URL of your choice.
I haven't tried this a long time. I'm sure you'll tell me if it works ... or does not. If it doesn't, it should and we'll fix it so it does.

Answer 2

As Ward suggested the EnityType I created did need one of its field to be marked as the key field. Besides that the EntityType also needs to have a defaultResourceName to be supplied to its constructor. I think this explains why the 'normal' query did work (the resourceName is supplied by from()) and why fetchEntityByKey did not work. The updated FileEntityType now looks like this:
var FileEntityType = new breeze.EntityType({
shortName: "File",
defaultResourceName: "files"
});
FileEntityType.addProperty(new breeze.DataProperty({
name: "id",
dataType: breeze.DataType.String,
isNullable: false,
isPartOfKey: true
}));
// These properties were not altered
FileEntityType.addProperty(new breeze.DataProperty({
name: "uri",
dataType: breeze.DataType.String,
isNullable: false
}));
FileEntityType.addProperty(new breeze.DataProperty({
name: "mTime",
dataType: breeze.DataType.Int16,
isNullable: false
}));
FileEntityType.addProperty(new breeze.DataProperty({
name: "type",
dataType: breeze.DataType.String,
isNullable: false
}));
FileEntityType.addProperty(new breeze.DataProperty({
name: "size",
dataType: breeze.DataType.int16,
isNullable: true
}));