<form:form action="test" method="POST" modelAttribute="test">
            <table>
                <tr>
                    <td><form:input path="id" /></td>
                    <td><form:input path="number" /></td>
                    <td><form:input path="str" /> </td>
                </tr>
                <tr>
                    <td colspan="3"><input type="submit" value="Ok" /> </td>
                </tr>
                
                <tr>
                    <td>${test.id}</td>
                    <td>${test.number}</td>
                    <td>${test.str}</td>
                </tr>
            </table>
        </form:form>

 @RequestMapping(value="/test",method= RequestMethod.GET)
    public ModelAndView show() {
        Test test = new Test();
        return new ModelAndView("testjsp", "test", test);
    }
    
    @RequestMapping(value="/test",method= RequestMethod.POST)
    public ModelAndView process(@ModelAttribute("test") Test test) {
        System.out.println(test.getId()+"\n");  //вот тут никаких NullPointerException 
        System.out.println(test.getNumber()+"\n"); //при не введении данных, просто id,number & str = null
        System.out.println(test.getStr()+"\n");
        return new ModelAndView("testjsp", "test", test);
    }

public class Test implements Serializable {

    private Integer id;
    private Long number;
    private Double str;

    //Getters and Setters
}