How can we use synchronous Datasource operations?

[vinobabu]

Hi All,

I am new to use/learn SmartGWT and stuck with a problem regarding Datasource. I have a Datasource fetch operation and the value I get from DSCallBack of this is processed in subsequent logic. But since the Datasource operations are asynchronous, am sometimes left with blank/null values.

Let me know if I am doing something wrong or if there is a way to do Synchronous calls to Datasource.

	private String setRoleField(String attribute) {
		Criteria rolefetchCriteria = new Criteria();
		rolefetchCriteria.addCriteria("searchFlag", 1);
		rolefetchCriteria.addCriteria("User_ID", attribute);

		requestProperties =new DSRequest();		
		requestProperties.setOperationId("outletRoleFetch");
		
		DataSource.get("recently_accessed_module").fetchData(rolefetchCriteria, new DSCallback() 
		{
			@Override
			public void execute(DSResponse dsResponse, Object data,
					DSRequest dsRequest) {
					
				
				Record[] record = dsResponse.getData();	
				outletRole = "";
				for(Record singlerecord: record)
					outletRole += "<font class='overview-subtitle'>"+singlerecord.getAttribute("OutletName")+"</font><font class='overview-time-label'>"+ singlerecord.getAttribute("Role")+"</font>";	

			}
			
	  },requestProperties);	

return outletRole;
	}

This code is always returning me "" empty value.

The Smartclient version am using is -->SmartClient Version: v10.0d_2014-09-09/EVAL Deployment

Thanks,
Babu

[Blama]

Hi vinobabu,

clientside DSRequests are always asynchronous. So your DSCallback-approach is correct.

Are you sure that your call returns any data? If not, your result would be correct, wouldn't it? Please check this in the Developer Console's RPC-tab. See the BuiltInDS sample for how to open the Developer Console.

Best regards,
Blama

[vinobabu]

Thanks for the reply Blama.

Yes I get DSResponse in Dev console, but the method in which the DS operation is happening doesn't return a valid value.

In other words, my function is returning value before the DSCallBack is received from the Datasource. I am thinking if this can be solved by making the Datasource operations Synchronous.

I am interested to know how this issue is solved universally across SmartGWT users. If we don't have the option to make a DSRequest Synchronous, how is the situation when DSRespose is not received in few seconds and the subsequent business logic is receiving "no Data".

Thanks and Regards,
Babu

[Blama]

Hi Babu,

I didn't see the return. Does this sample help?
Generally speaking you won't get rid of the asynchronous nature of SmartGWT/GWT/AJAX, so you'll do much work in Callbacks.

Best regards,
Blama

[edulid]

Hi Babu,
you can pass a callback object to your setRoleField method, which you can call when the data is available. So your setRoleField method returns void and the data is available via your callback.

[vinobabu]

Thanks edulid.

This sounds like a plan. Could you please provide me a prototype of it, which will help me more.

Thanks and Regards, Babu