How to Validate /check the input fields value exist in back end DB or not during live change in sapui5 - sapui5

Question

I have requirement where in need to create the record from SAPui5 application,
For that we have Form and enterthe all details and submit to the data base.
Now i need to validate the first field value, if that value exist in the system/DB need to populate the error, like this record already exist during livechange.
For E.g., Input fields are as follows.
Empld : 121
EmpName : tom
On Change of Empid value need to check 121 record exist in the database or not.
Following are the blogs refereed for the solution but didn't get the solution for the same.
https://blogs.sap.com/2015/10/19/how-to-sapui5-user-input-validations/
https://blogs.sap.com/2015/11/01/generic-sapui5-form-validator/
As i"m new to SAPUI5.Please help me with the coding.
Thanks in advance.

Answer 1

I don't know how much you are aware of Requests to the Backend but maybe you could make a Read Operation and check if there is any data returned:
First solution could be like this (with Entity key):
this.getOwnerComponent().getModel().read("/EntityPath", {
success: function(oData, response) {
if(oData.results.length === 0) {
console.log("Nothing found for this key");
}
},
error: function(oError) {
//Error Handling here
}
});
Or you could build a Filter, pass it to the read operation and check if there is any data returned:
var aFilter = new sap.m.Filter(new Filter("EmpId", sap.m.FilterOperator.EQ, "value"));
this.getOwnerComponent().getModel().read("/EntitySet", {
filters: aFilter,
success: function(oData, response) {
if(oData.results.length === 0) {
console.log("User is not available");
}
},
error: function(oError) {
//Error Handling here
}
});
However, this isn't the best way to check if there is already an entry in your database. You should do this in your Business Logic with Error Messages which get passed to the Frontend.
Hope this helps :-)