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Former Member
15,479

Hi All


Since the first release of SAPUI5 I started trying to use it with JSON and I did not find a way to pass callback functions to the loadData method of the JSON Model. While reading the SAPUI5 documentation I found two methods that can be used to attach handlers to the request completed and request failed events, but to be honest I didn't find it useful. So I decided to post a thread in the SCN forum.

After few weeks without answers I decided to take a look under the hood. When I opened the JSONModel.js file I saw where the loadData method calls the jQuery.ajax and I finally found what I was looking for, i.e., what I need to change to meet my requirements.

Figure 1 - JSON Model source code

Now that I knew what needed to be changed in the loadData method to received the callback functions as parameters the next question was: how to extend the JSON Model? Turning back to the SAPUI5 documentation I found the extend method which enables, as it’s name says, to extend the JSON Model.

Sharing the results

myJSONModel.js file with the JSON Model extension

How it was extended: a new method was declared (loadDataNew). Two new parameters (fnSuccess and fnError) were added to the method and the callback functions calls were inserted (see source code comments).

jQuery.sap.require("sap.ui.model.json.JSONModel");
sap.ui.model.json.JSONModel.extend("myJSONModel", {
          //declare our new method including two new parameters fnSuccess and fnError, our callback functions
          loadDataNew: function(sURL, fnSuccess, fnError, oParameters, bAsync, sType, bMerge, bCache){
                              var that = this;
                              if (bAsync !== false) {
                                        bAsync = true;
                              }
                              if (!sType)          {
                                        sType = "GET";
                              }
                              if (bCache === undefined) {
                                        bCache = this.bCache;
                              }
                              this.fireRequestSent({url : sURL, type : sType, async : bAsync, info : "cache="+bCache+";bMerge=" + bMerge});
                              jQuery.ajax({
                                url: sURL,
                                async: bAsync,
                                dataType: 'json',
                                cache: bCache,
                                data: oParameters,
                                type: sType,
                                success: function(oData) {
                                        if (!oData) {
                                                  jQuery.sap.log.fatal("The following problem occurred: No data was retrieved by service: " + sURL);
                                        }
                                        that.setData(oData, bMerge);
                                        that.fireRequestCompleted({url : sURL, type : sType, async : bAsync, info : "cache=false;bMerge=" + bMerge});
                                        // call the callback success function if informed
                                        if (typeof fnSuccess === 'function') {
                                             fnSuccess(oData);
                                         }
                                },
                                error: function(XMLHttpRequest, textStatus, errorThrown){
                                        jQuery.sap.log.fatal("The following problem occurred: " + textStatus, XMLHttpRequest.responseText + ","
                                                                      + XMLHttpRequest.status + "," + XMLHttpRequest.statusText);
                                        that.fireRequestCompleted({url : sURL, type : sType, async : bAsync, info : "cache=false;bMerge=" + bMerge});
                                        that.fireRequestFailed({message : textStatus,
                                                  statusCode : XMLHttpRequest.status, statusText : XMLHttpRequest.statusText, responseText : XMLHttpRequest.responseText});
                                         // call the callback error function if informed
                                        if (typeof fnError === 'function') {
                                             fnError({message : textStatus, statusCode : XMLHttpRequest.status, statusText : XMLHttpRequest.statusText, responseText : XMLHttpRequest.responseText});
                                         }
                                }
                              });
          }
});

and below is the code implemented in the index.html to exemplify its use


<!DOCTYPE html> 
<html><head> 
    <meta http-equiv='X-UA-Compatible' content='IE=edge' /> 
    <title>Extending the JSON Model</title> 
    <style>
        #firstname, #lastname, #btn1, #btn2, #btn3 { margin: 0 4px; }
        #content{ margin-top: 10px; }
    </style>
    <script id='sap-ui-bootstrap' type='text/javascript' 
        src='../../sapui5/resources/sap-ui-core.js' 
        data-sap-ui-theme='sap_goldreflection' 
        data-sap-ui-libs='sap.ui.commons'></script>  
    <script type='text/javascript' src='myJSONModel.js'></script>    
    <script> 
        //callback function for successful requests
       function request_success (oData) {
            if(oData.success){
                sap.ui.commons.MessageBox.alert('Data loaded successfully');
            }else{
                sap.ui.commons.MessageBox.alert(oData.msg);
            }
        }
        //callback function to handle communication errors
        function request_error () {
                  sap.ui.commons.MessageBox.alert(arguments[0].statusText);
        }
        //create the ApplicationHeader control
        var oAH = new sap.ui.commons.ApplicationHeader('appHeader', {
            logoSrc: 'http://www.sap.com/global/images/SAPLogo.gif',
            logoText: 'SAP SAPUI5 Library',
            displayLogoff: false
        });
        //create the label for field First name
        var oL1 = new sap.ui.commons.Label('l1', {
            text: 'First name:'
        });
                //create the label for field Last name
        var oL2 = new sap.ui.commons.Label('l2', {
            text: 'Last name:'
        });
        //create Input field First name
        var oTF1 = new sap.ui.commons.TextField('firstname', {
            value: '{/data/firstname}'
        });
        //create Input field Last name
        var oTF2 = new sap.ui.commons.TextField('lastname', {
            value: '{/data/lastname}'
        });
        //create our custom model
        var oModel = new myJSONModel;
        //set our model
        oTF1.setModel(oModel);
        oTF2.setModel(oModel);
        //create button to load data from server
        var oBtn1 = new sap.ui.commons.Button('btn1',{ 
            text:'Load data (ok)', 
            press:function(){
                oModel.loadDataNew("data_success.json", request_success, request_error);
            } 
        });
         //create button to load data from server
        var oBtn2 = new sap.ui.commons.Button('btn2',{ 
            text:'Load data (user not found)', 
            press:function(){
                oModel.loadDataNew("data_error.json", request_success, request_error);
            } 
        });
        //create button to load data from server
        var oBtn3 = new sap.ui.commons.Button('btn3',{ 
            text:'Load data (file not found error)', 
            press:function(){
                oModel.loadDataNew("filenotfound.json", request_success, request_error);
            } 
        }); 
        //create the layout
                var oLayout = new sap.ui.commons.layout.HorizontalLayout("Layout1", {
            content: [oL1, oTF1, oL2, oTF2, oBtn1, oBtn2, oBtn3]
        });
        //place our controls
        oAH.placeAt("appheader");
        oLayout.placeAt("content");
    </script>
</head>
<body class='sapUiBody'>
    <div id='appheader'></div>
    <div id='content'></div>
</body>
</html>

Screenshots

Figure 2 - Initial screen

Figure 3 - Success callback function called with results

Figure 4 - Success callback function called with no results


Figure 5 - Error callback function called (simulating a communication error)

The eclipse project with the complete source code can be downloaded from the url below.

http://jianelli.com.br/sap/scnblog1.zip

Your feedback is most welcome!

Christian Jianelli


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