Question

Explain how it is that we build the “processRequest()” method in a Servlet class, when the Servlet interface requires us to write 3 methods(init(), service() and destroy()). Why don’t we have to build these 3 methods?  

Answer 1

The "processReuest()" can be built without specifically writing the given 3 methods. The process for creation is mentioned below:

1. Add the following method declaration for processRequest(req, res). Add open and close parentheses ({, }) and position the cursor in between the parenthesis.

protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

2. Declare a variable employeeList of the List type that contains Employee objects. Declare the variable gson to process Gson object.

List<Employee> employeeList = null;

3. Instantiate the employeeList object by invoking getEmployees method of EmployeeBean.

employeeList = employeeBean.getEmployees();

4. Check if the employeeList is not NULL

if (employeeList != null) {

5. Set the content type to “application/json”

response.setContentType("application/json");

6. Invoke the method toJson(…) and convert the employeeList to JSON.

Copygson.toJson(employeeList,
            new TypeToken<ArrayList<Employee>>() {}.getType(),
response.getWriter());

7. End of if condition. Close the parenthesis (})

8. Add an else condition to cover the error scenario when the employeeList is empty.

Copyelse {
  response.setStatus(HttpServletResponse.SC_NOT_FOUND);
}