@ModelAttribute在方法签名中使用@ModelAttribute注释方法

Question

I was wondering if it is possible to chain @ModelAttribute methods by having an @ModelAttribute annotated, but not request mapped, method use another ModelAttribute in the method signature. This would be in a controller.

ie

@ModelAttribute("attrOne")
public AttrOne getAttrOne() {
    return service.getAttOne();
}

@ModelAttribute("attrTwo")
public AttrTwo getAttrTwo(@ModelAttribute("attrOne") AttrOne attrOne){
    return anotherservice.getAttrTwo(attrOne);      
}

Then if there was a request mapped method that did this:

@RequestMapping(method=RequestMethod.GET)
public String doSomething(@ModelAttribute("attrTwo") AttrTwo attrTwo )

would this work?

I seem to get a null object for AttrOne in the second annotated method... as the first annotated method is not called by the second one...

Cheers

Answer 1

I ran into the same situation by learning from the spring documention:

@ModelAttribute is also used at the method level [..] . For this usage the method signature can contain the same types as documented above for the @RequestMapping annotation.

I found SPR-6299 which faces this problem. In the comments you can find a workaround by providing only one @ModelAttribute annotated method which sets the attributes into the model:

@ModelAttribute
public void populateModel(Model model) { 
  model.addAttribute("attrOne", getAttrOne());
  model.addAttribute("attrTwo", getAttrTwo());
}

Answer 2

根据SPR-6299 ，这将在Spring 4.1 RC1或更高版本中实现。