DS Response is returning null due to JSON not being identified by DMI Handler

HI
I am migrating the existing application which runs on SmartClient 6.5.1 to version v91p_2014-05-30_Enterprise.

I am testing the application for compatibility with IE 8 which is currently being used.

The problem i face is when a call of Fetch is made from the application with a criteria, the call reaches the DMI Handler but the criteria is not getting received. I am pasing the criteria as aJSON

Example :
---------
Call from .js file:
----------------
DataSource.getDataSource("sample.ds.xml").fetchData({masterName:"searchString"},<<call back function>>);

sampleds.xml contains :
-----------------------

<operationBinding id="sample" operationType="fetch" sqltype="generic" serverMethod="fetchDataValue">
<serverObject lookupstyle="spring" bean="com.sample.Example"/>
</operationBinding>


the DMI Handler looks like this:
------------------------------

public Class Example {
public DSResponse fetchDataValue(MasterDetails master,DSRequest request) {
String masterName = master.getMasterName();

DSresponse response = new DSResponse();

response.setData(masterName);

}
}

MasterDetails.java
==============
public Class MasterDetails implements serializable {

private String masterName;

public String getMasterName() {

return masterName;
}

public setMasterName(String master) {

this.masterName = master;
}

}
Earlier the same code was working for 6.5.1 but for the latest version the DSResponse is null.

I am also not sure how the JSON object was getting mapped to this POJO which is now failing post Upgrade.

Kindly, please help

Regards

Mohammed Shahid Nawaz