java 中使用ajax调用后台方法注意事项

java 中使用ajax调用后台方法注意事项，后台方法一定要加@ResponseBody

    jQuery.validator.addMethod("checkRuleName",function(value, element) {
        var rst = false;
            //校验规则组合名称是否重复
            $.ajax({
                    type : "post",
                    cache : false,
                    async: false,//
                    url: '${ctx}/ProductPackageRule/Contro/checkRuleName',
                    //?groupName='+value
                    data:{'ruleName':value},
                    success : function(result) {
                        
                          
                         if(result=="0")
                            {
                                rst = true;
                            }                                            
                    }
                });    
        
        return rst;            
    },"规则名称重复!");    

后台代码：

@RequiresPermissions("/ProductPackageRule/Contro:view")
    @RequestMapping(value ="checkRuleName", method = { RequestMethod.GET, RequestMethod.POST })
    @ResponseBody    //一定要记得加上
    public int checkRuleName(String ruleName)
    {
        int k=1;
        ProductPackageRuleModel model = new ProductPackageRuleModel();
        model.setRuleName(ruleName);
        List<ProductPackageRuleModel> list = productPackageRuleDao.checkRuleName(model);
        if (list.isEmpty()) {
        k=0;
        }
        return k;
    }