CODEWITHSUNDEEP
odatasapui5
user557657
user557657

Reputation: 896

What is the difference between new sap.ui.model.odata.ODataModel and read?

I am playing around with a OData service and I am very confused when to use this 

var oModel = new sap.ui.model.odata.ODataModel("proxy/http/services.odata.org/V3/(S(k42qhed3hw4zgjxfnhivnmes))/OData/OData.svc");
this.getView().setModel(oModel);

vs 

var oModel = new sap.ui.model.odata.ODataModel("odatserviceurl", true);
var productsModel = new JSONModel();

oModel.read("/Products",
     null,
     null,
     false,
     function _OnSuccess(oData, response) {
         var data = { "ProductCollection" : oData.results };
         productsModel.setData(data);
     },
     function _OnError(error) {
         console.log(error);
     }
);
this.getView().setModel(productsModel);

I have two working example using both approach but I am not able to figure out why using read method if I can achieve same with first version. Please explain or guide me to the documentation which can clear my confusion.

Upvotes: 1

Views: 3126

Answers (1)

Rahul Bhardwaj
Rahul Bhardwaj

Reputation: 2353

Ok, lets start with the models:

  1. JSON Model : The JSON model is a client-side model and, therefore, intended for small datasets, which are completely available on the client. The JSON model supports two-way binding. NOTE: no server side call is made on filtering, searching, refresh.

  2. OData Model : The OData model is a server-side model: the dataset is only available on the server and the client only knows the currently visible rows and fields. This also means that sorting and filtering on the client is not possible. For this, the client has to send a request to the server. Meaning searching/filtering calls odata service again.

Now, lets look at scenarios where we will use these models:

Scenario 1: Showing data to user in a list/table/display form. Data manipulation is limited to searching and filtering. Here, I would use oData model directly to controls as only fetching of data is required.( your method 1) (NOTE: One way binding). Remember here all changes require a call to server.

Scenario 2: I have an application which has multiple inputs, user can edit changes, also some fields are calculated and mandatory. All in all, many user changes are done which may be temporary and user might not want to save them. Here, you dont want to send these temporary changes to backend as yet. You way want to manipulate, validate data before sending. Here, we will use JSON Model after reading data from odata model ( your method 2). Store the changes in local JSON model, validate and manipulate them and finally send the data using Odata create/update. Remember here all changes DO NOT require a call to server as data is present in local JSON MODEL.

Let me know if this helps you. :)

EDIT : Additional Information :

As per your comment :

Documentation says oModel.read' trigger get request but new sap.ui.model.odata.ODataModel("proxy/http/services.odata.org‌​/V3/(S(k42qhed3hw4zg‌​jxfnhivnmes))/OData/‌​OData.svc")` does the same thing so why and when to use oModel.read

Here, is where you misunderstood. The code new sap.ui.model.odata.ODataModel("proxy/http/services.odata.org‌​/V3/(S(k42qhed3hw4zg‌​jxfnhivnmes))/OData/‌​OData.svc") will NOT send a read/get Request. It calls the odata services and fetches the metadata of the service. A service can have multiple entities. For example: the service :http://services.odata.org/Northwind/Northwind.svc/ has mutiple entity sets such as Categories, Customers, Employees etc. So, when I declare : new sap.ui.model.odata.ODataModel("http://services.odata.org/Northwind/Northwind.svc/") it will fetch the metadata for service (not actual data). Only when you call the desired entity set, it will fetch the data. The Entity set is specified :

  1. When you call the read method ( like you have specified '/Products')
  2. Bind the entity set name directly to control like to List,Table etc ( items='{/Products}' )

Upvotes: 5

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