I have a requirement in my workflow where I have generate an excel report consisting of workflow properties as column headers in excel and values as the properties value's of all the completed workflow tasks.Can anyone please help me in this context.
To trigger it: Alfresco support java jobs triggered by crons. I believe that's what you need.
To create the file: The easy way out would be to convince your product owner to use a csv for this. Which is lighter and open. This way, you can just write your text directly to a newly created file. Otherwise, you'll have to include the excel-writer library of your choice (e.g. apache poi) and use this.
Then it all depends on the library you choose, and what kind of writer it's compatible with. But then it's plain java and nothing alfresco-specific anymore.