attribute value must be a constant.

Question

package spittr.web;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import spittr.data.SpittleRepository;

import static org.springframework.web.bind.annotation.RequestMethod.GET;

@Controller
@RequestMapping ( "/spittles" )
public class SpittleController {

    private SpittleRepository spittleRepository;
    private static final String MAX_LONG_AS_STRING = Long.toString(Long.MAX_VALUE) + "";

    @Autowired
    public SpittleController(SpittleRepository spittleRepository) {
        this.spittleRepository = spittleRepository;
    }

    @RequestMapping ( method = GET )
    public String spittles(
            Model model,
            @RequestParam ( value = "max", defaultValue = SpittleController.MAX_LONG_AS_STRING) long max,
            @RequestParam ( value = "count", defaultValue = "20" ) int count) {
        model.addAttribute(
                "spittleList",
                spittleRepository.findSpittles(max, count)
        );
        return "spittles";
    }
}

@RequestParam 里的defaultvalue传MAX_LONG_AS_STRING的时候提示错误attribute value must be a constant.可是我已经在上面设置MAX_LONG_AS_STRING为静态的了，为什么还会这样提醒。相反，如果我把上方设置成

private static final String MAX_LONG_AS_STRING = "50";

就不会报错.

求解这是为什么？如果涉及到编译和运行期间的原理，希望大佬详细解答。

Answer 1

恩，我找到了答案。。https://www.jianshu.com/p/f24...