有些情况为了偷懒，往往会使用注解来动态处理一些功能，比如Excel的导入以及导出等。但是一些情况下我们需要动态的修改注解的属性值，来完成一些特定场景的业务需求。

java动态修改注解的属性代码

    public void updateFieldAnnotationVal(String fieldName, String annoName, Class className, Object value ,Class annotation) throws Exception{
        Field field =  className.getDeclaredField(fieldName);
        //获取属性上面的注解
        Annotation annotation1 = field.getAnnotation(annotation);
        //获取动态代理对象
        InvocationHandler invocationHandler = Proxy.getInvocationHandler(annotation1);
        //获取 AnnotationInvocationHandler 的 memberValues 字段
        Field memberValues = invocationHandler.getClass().getDeclaredField("memberValues");
        //由于属性私有,必须打开权限
        memberValues.setAccessible(true);
        //修改属性值
        Map map = (Map) memberValues.get(invocationHandler);
        map.put(annoName, value);
    }

调用代码

    @GetMapping("/studentMajor/getStudentMajorExcelTemplate")
    public void getStudentMajorExcelTemplate(StudentMajorVo param, PageRequestVo pageRequestVo) throws Exception {
        HashMap<String, String[]> boxMap = new HashMap<>();
        Integer userType = param.getUserType();
        if (UserType.SCHOOL == userType) {
            this.updateFieldAnnotationVal("majorId", "importField", StudentMajorExcel.class, false, Excel.class);
            this.updateFieldAnnotationVal("schoolName", "importField", StudentMajorExcel.class, false, Excel.class);
        }
        if (UserType.DEPARTMENT == userType) {
            this.updateFieldAnnotationVal("majorId", "importField", StudentMajorExcel.class, true, Excel.class);
            this.updateFieldAnnotationVal("schoolName", "importField", StudentMajorExcel.class, true, Excel.class);
        }
        ExcelsUtil.exportCommonTemplate(StudentMajorExcel.class, boxMap);
    }