You need to set the Content variable.
You might want to look at the examples:
Thank you so much, I had set the content variable but what I hadn't set was the result mapping. Your first link helped me to find my mistake. I spent several days to find this. Thanks again.
can u post a link to the thread where i can find the code u hav posted.
I can't exactly find the link that I refered before. But I think, the second link that bpmn2user posted before will help you. Almost all the required things except "result mapping" are shown there. Go to his first link and look at 4th screenshot to identify how to do result mapping.