[novikov]

Для такого запроса
api/objects/15?...

http://docs.sencha.com/extjs/6.0/6.0...t-cfg-appendId

Ext.define('Object', {
    extend: 'Base',

    idProperty: 'ObjId',

    fields: [
        { name: 'ObjId', type: 'int' },
        { name: 'Name', type: 'string' },
    ],

    proxy: {
        type: 'rest',
        url : 'api/objects'
    }

});