How to fetch multiple values and display in textbox from database on selection of <option> in jsp

You first need to write onchange event handler so whenever select-box value gets changes this handler will get called and then send the value of select to backend page(servlet) .So, ajax code will look like below :

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
  $('select#selectBox').on('change', function() {
     var value = $(this).val(); //get value from select-box
      $.ajax({
        type: 'POST',//can be post request or get 
        url: url,//put url here where you need to send
        data: {
          'value': value//pass value 
        },
        success: function(response) {
          //result will come here 
           //if recieve as html use           
          $("somedivclass").html(response)        
          //if recieve as separted commas         
          var result = response.split(",")
          //access same using result[0],result[1] ..etc
          //add value to input using
          $("#loginid").val(result[0]);
         //same for other  
    
        }
      });
    })

At your server end get that value which is passed from ajax using request.getParameter("value") inside doPost method of ajax if making POST request.Then ,simply write your query to retrieve record from db and send back same to ajax .So , your code will look like somewhat below :

String value = (String) request.getParameter("value");
String query = "select * from Users where yourcolumnanemtocompare=?";
PreparedStatement ps = con.prepareStatement(query);
ps.setString(1, value);
ResultSet rs = ps.executeQuery();
//if value there 
String text;
if (rs.next()) {
  //change value accordingly..i.e : rs.getstring..
  text = "<input id=" + loginid " type="
  text " value=" + rs.getInt(1) + " /><input id="
  firstname " type="
  text " value=" + rs.getInt(2) + " /> <input id="
  lastname " type="
  text " value=" + rs.getInt(3) + " /><input id="
  address " type="
  text " value=" + rs.getInt(4) + " />";
}

response.setContentType("text/html"); // Set content type 
response.setCharacterEncoding("UTF-8");
response.getWriter().write(text); // response to send back.
//or
if (rs.next()) {
  //change value accordingly..i.e : rs.getstring..
  text = rs.getInt(1) + "," + rs.getInt(2) + "," + rs.getInt(3) + "," + rs.getInt(4);
}
response.setContentType("text/plain"); // Set content type 
response.setCharacterEncoding("UTF-8");
response.getWriter().write(text); // response  to send back..
//or use json to send data..