How to put result sent by servlet into html input box?

Question

HTML FILE

<form method = "post"  action = "getSum">
     Enter first no. : <input type = "text" name = "First"/>
     Enter Second no.: <input type = "text" name = "Second"/>
     SUM :             <input type = "text" name = "Sum"/>    
</form>

sum.java

package calculation;


public class sum extends HttpServlet {
private static final long serialVersionUID = 1L;

public sum() {
    super();
  }

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

}

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

    int first = Integer.parseInt(request.getParameter("First"));
    int second = Integer.parseInt(request.getParameter("Second"));
    int sum = first+second;
    PrintWriter out = response.getWriter();
    out.println("");


}

}

I want to put the result sent by servlet into the input box which i made in html file how to do that? I am new to servlet programming pls help me out a little bit

score 2 · Accepted Answer · edited May 23 '17 at 12:07

In short.

Create the form in the doGet() method of the servlet. In the action attribute, specify the name of the servlet in the method attribute, specify POST.

  ...
  response.setContentType("text/html");
  PrintWriter out = response.getWriter();
  out.println(...) // form here
  ...

You can use *.html file instead of creating the form in the servlet.

Get the passed parameters in the doPost() method of the servlet.

...
request.getParameter("First");
request.getParameter("Second");
request.getParameter("Sum");
...

Perform the necessary checks, generate the form with the filled fields.

Then call the servlet you will see the blank form. Write values in the fields and submit the form. You will see the filled form.

Although it is better to use JSP in this case - What is the difference between JSF, Servlet and JSP?

i want that when i returned the page from server it has a html input box type=text and have value in the box equal to the sum — sony, Feb 11 '16 at 18:47

score 1 · Answer 2 · answered Feb 11 '16 at 18:03

There are a lot of possibilities for client-server interaction. I see two common cases:

After user presses the button the server returns a full HTML page for a client. In your code you can simple modify out.println(""); line in the Servlet and add a submit button in HTML form to achieve this. But in practice you need something for generating dynamic HTML pages, you can use JSP or template engine like Velocity, FreeMarker or something else. Also there are a lot of frameworks.
Use AJAX. After pressing the button the server returns some data to client (for example in JSON format) and client don't reload the HTML page but can refresh some part of it (i.e. in your case update an input box value). In this case you should write some JavaScript code on client-side for sending request (instead of using default HTML form submit) and update page data. You can use JQuery to simplify your work (or other library). In the Servlet you need to parse clients request and make a response. There are also a lot of libraries and frameworks that you can use. For example Gson for parsing/generating JSON or spring-web framework.

score 0 · Answer 3 · answered Feb 11 '16 at 17:58

The simplest is to have all the HTML generated in your servlet. When doGet is called, return the empty HTML form. When doPost() is called, return the HTML form with the data populated.

doGet(...){
   out.println("<html> ... <form> .... </form> ... </html>
}

doPost(...){
   out.println("<html> ...<form> populate inputs </form> ... </html>");
}

You could also create a new method

renderHtml(Integer first, Integer second, Integer sum) {
   // print out html. If first, second, or sum is null, then don't add those to
   // the value of the input boxes
}

which you call do eliminate duplicating code.

The next level is to use a templating system like: jsp, Velocity, FreeMarker, etc ....

i want that when i returned the page from server it has a html input box type=text and have value in the box equal to the sum — sony, Feb 11 '16 at 18:39

How to put result sent by servlet into html input box?

3 Answers3