如何为@RequestParam的defaultValue提供表达式

Question

I have a controller where a RequestParam is used. Like this

@RequestMapping("/hello")
public ModelAndView process(
        @RequestParam(value = "startDate", 
                      required = false, 
                      defaultValue="yesterday()") startDate)

If the startDate is not specified a defaultValue is used. But in my case the value should be dynamic eg now() or yesterday() . Is there any way to specify an expression eg method of class to return the value?

I am too lazy to use code like this everywhere

startDate=startDate!=null ? startDate : new Date()

UPDATE Ideally I would like to write custom expression to provide eg start of current week or end of current month if the date is not specified

Answer 1

As explain here https://stackoverflow.com/a/22523299/636472 :

You can handle your case by create a behavior for a special word:

@InitBinder
public void initBinder(WebDataBinder binder) throws Exception {
    final DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
    final CustomDateEditor dateEditor = new CustomDateEditor(df, true) {
        @Override
        public void setAsText(String text) throws IllegalArgumentException {
            if ("today".equals(text)) {
                setValue(new Date());
            } else {
                super.setAsText(text);
            }
        }
    };
    binder.registerCustomEditor(Date.class, dateEditor);
}

---

@RequestParam(required = false, defaultValue = "today") Date startDate

Answer 2

The defaultValue has to be a final static expression. However there is a thing which you can do by using a custom annotation.

eg

create a custom annotation @customAnno apply this annotation to which ever methods you want.

using aspect @before("@customAnno") catch this method and check whether it have the value you want or you change the value you want at runtime.