We need to have the following jsp tag to data bind your entity to the jsp form fields:
The form is from the spring tag library:
The following is the not the full html, but I hope you can relate your self:
<%@taglib uri="http://www.springframework.org/tags/form" prefix="form"%>
<form:form action="save" method="post" modelAttribute="patient">
<table>
<tr>
<td>Name</td>
<td>
<form:input path="patient.patient_name" /> <br />
</td>
</tr>
<tr>
<td>Phone</td>
<td>
<form:input path="patient.phone_number" /> <br />
</td>
</tr>
<tr>
<td colspan="2"><button type="submit">Submit</button></td>
</tr>
</table>
</form:form>
The form has to be processed twice , once before rendering the form, during which we need to give the appropriate bean instantiation for the property value modelAttribute="patient".
- For this the controller class(at the class defintion level) you need to have
@RequestMapping annotation.
- You need to have the handler method parameters as follows
@GetMapping("logincreate")
public String handleLoginCreate(@ModelAttribute("login") Login login, Model model)
{
System.out.println(" Inside handleLoginCreate ");
model.addAttribute("login",login);
return "logincreate";
}
Spring will scan all handler methods @ModelAttribute and instantiate it with default constructor of Login class, and call all of its getters and setters (for the jsp binding from form to the "login"). In case of missing any of the following the jsp will not be shown, various exceptions are thrown
- getters/setters
- default constructor
- model.addAttribute("login",login);
- class level @RequestMapping
- method parameter level @ModelAttribute
Also, the handler method of action in the jsp, the in the above form action="save", also the handler method might look like this:
@PostMapping("save")
public String saveLoginDetails(@ModelAttribute("login") Login login, Model model) {
//write codee to insert record into DB
System.out.println(" Inside save login details ");
System.out.println("The login object is " + login.toString());
System.out.println("The model object contains the login attribute"+ model.getAttribute("login"));
loginService.saveLogin(login);
return "welcome";
}
Important learning is:
- Before form is launched, spring should have appropriate annotation to indicate the backing bean of the form, in the above example the "backing bean" or "binding object" is Login login with appropriate handler method's parameter annotation
@ModelAttribute("login") Login login
