使用场景:

这个场景是在Excel一对多,多对多模板导出场景下遇到的,常见的场景有财务报表,绩效报表等,存在嵌套循环的情况下,我们就需要获取对象的最大深度,以此实现循环插入,下面的行往下移动数据的最大宽度,直接贴代码

1.新建DO对象

2.标记为自定义java对象

我这里使用了ExcelDTO注解做标记,也可自定义实现接口的方式做标记

3.获取集合最大深度

4.测试

public class PerformanceService {

 /**
     * 标记是否是导出对象
     */
    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.TYPE)
    public @interface ExcelDTO {

    }

    @ExcelDTO
    public static class User implements Serializable {

        public User() {
        }

        public User(Integer age, String username) {
            this.age = age;
            this.username = username;
        }

        public User(List<User> userList, Integer age, String username) {
            this.userList = userList;
            this.age = age;
            this.username = username;
        }


        public User(User user, List<User> userList, Integer age, String username) {
            this.user = user;
            this.userList = userList;
            this.age = age;
            this.username = username;
        }

        private User user;

        public User getUser() {
            return user;
        }

        public void setUser(User user) {
            this.user = user;
        }

        private List<User> userList = Lists.newArrayList();

        public List<User> getUserList() {
            return userList;
        }

        public void setUserList(List<User> userList) {
            this.userList = userList;
        }

        private Integer age;

        private String username;

        public Integer getAge() {
            return age;
        }

        public void setAge(Integer age) {
            this.age = age;
        }

        public String getUsername() {
            return username;
        }

        public void setUsername(String username) {
            this.username = username;
        }
    }


   private static Integer getObjectMaxSize(Collection<?> datas) throws Exception {
        Integer maxSize = 0;
        for (Iterator iterator = datas.iterator(); iterator.hasNext(); ) {
            Object object = iterator.next();
            maxSize += getMaxSize(object.getClass().getDeclaredFields(), object,new AtomicInteger(0));
        }
        return maxSize;
    }


    private static boolean isJavaClass(Class<?> clz) {
        Annotation[] annotations = clz.getAnnotations();
        for (Annotation annotation : annotations) {
            if (annotation.annotationType().getSimpleName().equals("ExcelDTO")) return true;
        }
        return false;
    }

    private static String getMethodName(String fildeName) throws Exception {
        byte[] items = fildeName.getBytes();
        items[0] = (byte) ((char) items[0] - 'a' + 'A');
        return new String(items);
    }

    private static Integer getMaxSize(Field[] declaredFields, Object obj, AtomicInteger loopNum) throws Exception {
        Integer tempNum = 1;
        int current=loopNum.get();
        if(!loopNum.compareAndSet(current,current+1)||current>10){
            throw new RuntimeException("对象子集引用超过深度");
        }
        for (Field field : declaredFields) {
            if (!field.isAccessible()) field.setAccessible(true);
            if (field.getType() == List.class && isJavaClass((Class<?>) ((ParameterizedType) field.getGenericType()).getActualTypeArguments()[0])) {//list类型
                List listObject;
                Method getListMethod = obj.getClass().getDeclaredMethod("get" + getMethodName(field.getName()));
                listObject = (List) getListMethod.invoke(obj);
                if (null == listObject || listObject.isEmpty()) {
                    continue;
                }
                Integer size = listObject.size();
                tempNum = size;
                for (int i = 0; i < size; i++) {
                    Object listDeclaredObj = listObject.get(i);
                    if (null == listDeclaredObj) {
                        continue;
                    }
                    tempNum -= 1;
                    tempNum += getMaxSize(listDeclaredObj.getClass().getDeclaredFields(), listDeclaredObj,loopNum);
                }
            } else if (isJavaClass(field.getType())) {//普通java类型
                Object javaObj;
                Method getListMethod = obj.getClass().getMethod("get" + getMethodName(field.getName()));
                javaObj = getListMethod.invoke(obj);
                if (null == javaObj) {
                    continue;
                }
                tempNum-=1;
                tempNum += getMaxSize(field.getType().getDeclaredFields(), javaObj,loopNum);
                continue;
            }
        }

        return tempNum;
    }
}

 public static void main(String[] args) throws Exception {
        ArrayList<User> obj = Lists.newArrayList();
        User one = new User(1, "礼拜");
        User two=new User(2,"ABC");
        User three=new User(2,"dgf");
        User fourths=new User(2,"hec");
        User fourths2=new User(2,"hec");
        User fourths3=new User(2,"hec");
        User fourths4=new User(2,"hec");
//        one.getUserList().add(two);
//        one.getUserList().add(two);
        one.setUser(three);
        three.getUserList().add(fourths);
        three.getUserList().add(fourths2);
        three.getUserList().add(fourths3);
        three.getUserList().add(fourths4);
        obj.add(one);
        System.out.println(getObjectMaxSize(obj));
//        System.out.println(new AtomicInteger(1).compareAndSet(1, 2));

    }