How to make options in combobox dependent on the selected option in first combobox using jsp and servlet dynamically

• Workflow :

       <select id="workflowId" name="workflowId" >

      <option value="0">Select Workflow</option>

" >

• Roles :

       <select id="workflowId" name="workflowId" >

      <option value="0">Select Roles</option>

" >

I need when i select workflow, options of roles loads dependent on workflow