Using Html
1) File --> New --> Spring Starter Project
2) Name --> Calculator
3) Select Maven as Type
4) Click Next
5) Add Dependencies: DevTools, Web, Thymeleaf
6) Click Next, Finish
7) Go to src/main/java --> Create a package called com.example.demo.controller
8) Now, right click the newly created package.
9) Create a class -> Calc_Controller
10) Add @Controller annotation
11) Add below content:
@GetMapping("/")
public String show_calculator()
{
return "calc";
}
12) Now, go to src/main/resources --> templates
13) Create a filed named as 'calc.html'
<!DOCTYPE html> <html xmlns:th="httptp://th:text=" ${results}"www.thymeleaf.org"> <head> <title> Calculator</title> </head> <body> <form action="calculate_values" method="post"> <label> Number 1: </label> <input type="number" name="num1"> <br><br> <label> Number 2: </label> <input type="number" name="num2"> <br><br> <select name="operations"> <option value="+"> Add </option> <option value="-"> Subtract </option> <option value="*"> Multiply </option> <option value="/"> Divide </option> </select> <br><br> <input type="submit" value="Calculate"> </form> <h2> Result </h2> <br> <p> <span th:text="${no1}"> </span> <span th:text="${ops}"> </span> <span th:text="${no2}"> </span> <span> = </span> <span th:text="${result}"> </span> </p> </body> </html> 14) Create Mapping for /calculate_values [action of form]
@RequestParam
Annotation which indicates that a method parameter should be bound to a web request parameter.
15) Create below method in Controller:
package com.example.demo.controller; import org.springframework.stereotype.Controller; import org.springframework.ui.Model; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.RequestParam; @Controller public class calc_controller { @GetMapping("/") public String show_controller() { return "calc"; } @PostMapping("/calculate_values") public String claculations(@RequestParam double num1,@RequestParam double num2,@RequestParam String operations,Model model) { //System.out.println(num1+num2); model.addAttribute("no1",num1); model.addAttribute("ops",operations); model.addAttribute("no2",num2); double result=0; switch(operations) { case "+":result=num1+num2;break; case "-":result=num1-num2;break; case "*":result=num1*num2;break; case "/":result=num1/num2;break; } model.addAttribute("result",result); return "calc"; } } http://localhost:8080/calculate_values
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