说明：通过已知的属性名称，从对象里获取数据的方式

1 通过将Object转为Map

public static Object getPropertyValue(Object t,String objProperty){
        Map<String, String> objMap = null;
        try {
            objMap = BeanUtils.describe(t);
            return objMap.get(objProperty);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

2 通过invoke方式

public static Object getFieldValueByName(Object o,String fieldName) {
        try {
            String firstLetter = fieldName.substring(0, 1).toUpperCase();
            String getter = "get" + firstLetter + fieldName.substring(1);
            Method method = o.getClass().getMethod(getter, new Class[] {});
            Object value = method.invoke(o, new Object[] {});
            return value;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

测试

public static void main(String[] args) {
        Exam exam = new Exam();
        exam.setTag("AAAAAA");
        System.out.println(getFieldValueByName(exam,"tag"));
        System.out.println(getPropertyValue(exam,"tag"));

    }

结果

AAAAAA
AAAAAA