Dinesh on Java

1.

@Controller
public class MyController {
 
    @ModelAttribute("myobject")
    public MyObject getInitializedMyObject() {
        return myService.getInitializedObject();
    }
 
    @RequestMapping(value="/handle.htm", method=RequestMethod.GET)
    public ModelAndView handleRequest() {
        return new ModelAndView("myView");
    }
 
}

In this example, the value returned by getInitializedMyObject is added to the Model. The View would be able to retrieve this object using the key “myobject” from the request attributes.

2.

@Controller
public class MyController {
 
    @ModelAttribute("myobject")
    public MyObject getInitializeMyObject() {
        return myService.getInitializedObject();
    }
 
    @RequestMapping(value="/handle.htm", method=RequestMethod.GET)
    public ModelAndView handleRequest(@ModelAttribute("myobject") MyObject myObject) {
        myObject.setValue("test");
        return new ModelAndView("myView");
    }
 
}

In this case, the getInitializeMyObject is executed first and the result is stored in a temporary map. This value is then passed as a parameter to the handler method. And finally myObject is added to the model for the views.

3.

@Controller
@SessionAttributes("myobject")
public class MyController {
 
    @RequestMapping(value="/handle.htm", method=RequestMethod.GET)
    public ModelAndView handleRequest(@ModelAttribute("myobject") MyObject myObject) {
        myObject.setValue("test");
        return new ModelAndView("myView");
    }
 
}

In this case, Spring searches for “myobject” in the session and pass it as the parameter to the handler method. If “myobject” is not found in the session, then HttpSessionRequiredException is raised.

4.

@Controller
public class MyController {
 
    @RequestMapping(value="/handle.htm", method=RequestMethod.GET)
    public ModelAndView handleRequest(@ModelAttribute("myobject") MyObject myObject) {
        myObject.setValue("test");
        return new ModelAndView("myView");
    }
 
}

In this case, a new instance of MyObject is created and then passed to handler method. If MyObject is an interface or an abstract class, then a BeanInstantiationException is raised.