optional POST parameter in spring MVC?

Question

I have the following code:

@RequestMapping(method = RequestMethod.POST)
public ModelAndView editItem(String name, String description)

However, sometime description is not passed in (this is a simplified example than the real one), and i would like to make description optional, perhaps by filling in a default value if none is passed in.

Anyone have any idea how to do that?

thanks a lot!

Jason

Lymphosarcoma

Answer 1

Instead of using @RequestParam for the optional parameters, take a parameter of type org.springframework.web.context.request.WebRequest. For example,

@RequestMapping(method = RequestMethod.POST)
public ModelAndView editItem(
  @RequestParam("name")String name,
  org.springframework.web.context.request.WebRequest webRequest)
{
  String description = webRequest.getParameter("description");

  if (description  != null)
  {
     // optional parameter is present
  }
  else
  {
    // optional parameter is not there.
  }
}

Note: See below (defaultValue and required) for a way to solve this without using a WebRequest parameter.

Murmur

better solution below! – Abstemious

different solution below (required = false) – Murmur

Answer 2

If you are using Spring MVC 3.0 or higher then just set defaultValue parameter of @RequestParam:

public ModelAndView editItem(@RequestParam(value = "description", defaultValue = "new value") String description)

In Spring MVC 2.5, I suggest to mark value as required = false and check their value against null manually:

public ModelAndView editItem(@RequestParam(value = "description", required = false) String description) {
    if (description == null) {
        description = "new value";
    }
    ...
}

See also corresponding documentation about @RequestParam annotation.

---

UPDATE for JDK 8 & Spring 4.1+: now you could use java.util.Optional like this:

public ModelAndView editItem(@RequestParam("description") Optional<String> description) {

    item.setDescription(description.getOrElse("default value"));

    // or only if it's present:
    description.ifPresent(value -> item.setDescription(description));
    ...
}

Bicorn

I think this method is much cleaner than including the WebRequestParameter. – Toffee

Also note that if your request parameter is a primitive (like int) and you mark it as required=false, you will want to use a wrapper class (like Integer) instead so that it can be passed as a null value to the controller method if the request parameter was not present. – Toffee

This can be used for @RequestHeader as well! – Presentable

The 'value = ' part is optional. – Crackbrain