Spring MVC - parameter binding

Question

How come this code just works? I didn't specify any custom converter or annotation (like @RequestBody or @ModelAttribute ) before argument ? Request is filled correctly from this GET call:

http://localhost:8080/WS/foo?token=C124EBD7-D9A5-4E21-9C0F-3402A1EE5E9B&lastSync=2001-01-01T00:00:00&pageNo=1

Code:

@RestController
@RequestMapping(value = "/foo")
public class FooController {

    @RequestMapping(method = RequestMethod.GET)
    public Result<Foo> excursions(Request request) {    
        // ...
    }   

}

Request is just POJO with getters and setters. I use it to shorten argument code because plenty methods uses those same arguments ...

public class Request {

    private String token;
    @DateTimeFormat(pattern = IsoDateTime.DATETIME)
    private Date lastSync;
    private Integer pageNo;

    // getters and setters

}

This was my original method before introducing Request.

@RestController
@RequestMapping(value = "/foo")
public class FooController {

    @RequestMapping(method = RequestMethod.GET)
    public Result<Foo> excursions(@RequestParam String token, @RequestParam @DateTimeFormat(pattern = IsoDateTime.DATETIME) Date lastSync, @RequestParam Integer pageNo) {
        // ...
    }

}

Answer 1

Request parameters will be mapped to POJOs, as it is happening in your case, by default. Additionally, if you use @ModelAttribute , an attribute in the Model will be created. That attribute can be then used in views, eg JSPs, to access the object.

@RequestBody annotation tells that the body of the request is NOT a set of form parameters like

token=C124EBD7-D9A5-4E21-9C0F-3402A1EE5E9B&lastSync=2001-01-01T00:00:00&pageNo=1

but is in some other format, such as JSON.

Answer 2

This is a feature provided by Spring MVC:

Customizable binding and validation. Type mismatches as application-level validation errors that keep the offending value, localized date and number binding, and so on instead of String-only form objects with manual parsing and conversion to business objects.

You can see it in the doc: http://docs.spring.io/spring/docs/4.2.x/spring-framework-reference/htmlsingle/