GWT-RPC DataSource implementation

[alius]

[from Isomorphic: we strongly recommend against using GWT-RPC for reasons listed in the FAQ. The approach is this thread should only be used as a temporary solution and only if you have a large set of pre-existing GWT-RPC services]

Hi All,
After some testing already provided GWT-RPC data source implementation (sticky post) (it was good starting point) I've decided to write my own. After reading post on how to implement Google Gears ( http://forums.smartclient.com/showthread.php?t=1192 ) I've realized that SmartClient already has possibility to use custom servers to load data. After checking SmartClient sources I've found protocol (which is not included in smartGWT) - "clientCustom". Using this protocol in data source allows to call custom server on data operations. It is done by overriding transformRequest method. When protocol is set to "clientCustom" - SmartClient after calling transformRequest method expects call of method processResponse after asynchronous call to server finishes.
The only thing is missing - possibility to set "clientCustom" protocol in smartGWT.
Here is what you can do:
- download smartGWT sources
- edit file main/src/com/smartgwt/client/types/DSProtocol.java - add these lines just after enumeration declaration :

    /**
     * dsRequest.data should be poplulated by custom call to server in transformRequest method. transformRequest should issue async request
     * to server and call processResponse on completion with created DSResponse object. If call was successful status and data should be filled.
     * If call was unsuccessful only status should contain error code.
     */
    CLIENTCUSTOM("clientCustom"),

- build your own smartGWT as it is described in http://code.google.com/p/smartgwt/wiki/BuildingFromSVN

I really hope that smartGWT developers will include it in future releases.

Please find attached implementation of GWT-RPC data source
Working example with real GWT RPC services I will upload in next response - can not upload more than 5 files.

Any comments are welcome.

Aleksandras

[alius]

Hi again.
As promised - uploading working example of GWT-RPC data source.

files in client package:
GwtRpcDataSource.java
TestDataSource.java
TestRecord.java
TestServiceAsync.java
TestService.java

files in server package:
TestServiceImpl.java

Aleksandras

[jasonzhang2002]

This is a much clear implementation.


thanks

-jason

[hickum]

I agree this seems like a very clean approach... with the exception of having to alter the DSProtocol class.

Isomorphic -- any chance this will be included in a future build?

[jasonzhang2002]

You may not need to recompile/rebuild. use this hack:
setAttribute("dataProtocol", "clientCustom", false);
in DataSource.

-jason

[hickum]

Sweet. Thanks.

[Isomorphic]

Nice job Alius. Just FYI, those APIs (dataProtocol:"clientCustom" and the processResponse() method) were added to SmartClient precisely to enable GWT-RPC integration, but Alius was faster in creating a sample than we were :)

Relative to the other recently posted approach for GWT-RPC integration, the approach Alius has demonstrated has the advantage that paging could be implemented if the GWT-RPC service supports it.

One thing to correct - in TestDataSource.java it's assumed that a grid is initiating the requests. It would be more correct to use dsRequest.getOldValues() to get the originally submitted values (works with any component).

[sjivan]

The "clientCustom" enum has been added to DSProtocol in SVN.

[alius]

Hi Isomorphic,

Thank you for correction.
Problem is that there is no method getOldValues() in DSRequest class (in smartGWT).

For the time being I've written my own version of combining original values with changes.

Please find an updated version of TestDataSource.java

Hi Sanjiv,

I've written some code which can be added to DSRequest to address this issue.
If you will find it suitable - please add it to next release.

    /**
    * The original record without changes.
    *
    * @param oldValues Original record without changes. Default value is null
    */
    public void setOldValues(ListGridRecord oldValues) {
        setAttribute("oldValues", oldValues);
    }
    /**
     * The original record without changes.
     *
     *
     * @return ListGridRecord
     *
     */
    public ListGridRecord getOldValues()  {
        JavaScriptObject oldValues = getAttributeAsJavaScriptObject ("oldValues");
        return new ListGridRecord (oldValues);
    }

    /**
     * Returns record where changes are combined with original values.
     *
     *
     * @return ListGridRecord
     */
    private ListGridRecord getEditedRecord () {
        // Retrieving values before edit
        JavaScriptObject oldValues = getAttributeAsJavaScriptObject ("oldValues");
        // Creating new record for combining old values with changes
        ListGridRecord newRecord = new ListGridRecord ();
        // Copying properties from old record
        JSOHelper.apply (oldValues, newRecord.getJsObj ());
        // Retrieving changed values
        JavaScriptObject data = getData ();
        // Apply changes
        JSOHelper.apply (data, newRecord.getJsObj ());
        return newRecord;
    }

Aleksandras

[ebardet]

Just reacting to

the approach Alius has demonstrated has the advantage that paging could be implemented

Any reason why getStartRow returns an int where getEndRow returns an Integer? Or this is just a glitch.

Emmanuel