Java集合List转树结构工具类

骑猪看日落 2022-11-18 13:55 188阅读 0赞

此版本太累赘,请转到函数版:[https://blog.csdn.net/wenxingchen/article/details/115749782?spm=1001.2014.3001.5501][https_blog.csdn.net_wenxingchen_article_details_115749782_spm_1001.2014.3001.5501]

业务场景:菜单树、组织架构树.....前端要求数据结构为树结构,而后端查出来的是一条一条的数据集,每次都要各种递归遍历很麻烦,特此写了一个工具类来解决.

*  三个注解:

import java.lang.annotation.ElementType;
    import java.lang.annotation.Retention;
    import java.lang.annotation.RetentionPolicy;
    import java.lang.annotation.Target;
    
    /**
     * @author sunziwen
     * @since 2021-4-13 16:19:05
     */
    @Target({ElementType.FIELD})
    @Retention(RetentionPolicy.RUNTIME)
    public @interface TreeId {
    }

一个工具类:

import cn.hutool.core.util.StrUtil;
    import lombok.SneakyThrows;
    
    import java.lang.reflect.Field;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    import java.util.Arrays;
    import java.util.List;
    import java.util.stream.Collectors;
    
    /**
     * 树形工具类
     *
     * @author sunziwen
     * @since 2021-4-13 16:19:05
     */
    
    public class TreeUtil {
        /**
         * 找出顶层节点
         *
         * @return data
         */
        @SneakyThrows
        private <T> List<T> treeOut(List<T> list) {
            //数据不能为空
            if (list == null || list.size() <= 0) {
                return list;
            }
            //获取泛型T的class
            Class<?> aClass = list.get(0).getClass();
    
            Field[] declaredFields = aClass.getDeclaredFields();
            //获取主键属性
            List<Field> idPropertyField = Arrays.stream(declaredFields).filter(x -> {
                TreeId annotation = x.getAnnotation(TreeId.class);
                return annotation != null;
            }).collect(Collectors.toList());
            if (idPropertyField.size() <= 0) {
                throw new RuntimeException("缺失@TreeId注解");
            }
            if (idPropertyField.size() > 1) {
                throw new RuntimeException("@TreeId注解只能存在一个");
            }
            //获取父节点属性
            List<Field> parentIdPropertyField = Arrays.stream(declaredFields).filter(x -> {
                TreeParentId annotation = x.getAnnotation(TreeParentId.class);
                return annotation != null;
            }).collect(Collectors.toList());
            if (parentIdPropertyField.size() <= 0) {
                throw new RuntimeException("缺失@ParentId注解");
            }
            if (parentIdPropertyField.size() > 1) {
                throw new RuntimeException("@ParentId注解只能存在一个");
            }
    
            /*主键的属性名*/
            String idPropertyName = idPropertyField.get(0).getName();
            /*主键的get方法*/
            Method getId = aClass.getMethod("get" + StrUtil.upperFirst(idPropertyName));
    
            /*父节点的属性名*/
            String parentIdPropertyName = parentIdPropertyField.get(0).getName();
            /*父节点的get方法*/
            Method getParentId = aClass.getMethod("get" + StrUtil.upperFirst(parentIdPropertyName));
    
            /*所有元素的Id*/
            List<Object> ids = list.stream().map(x -> {
                try {
                    return getId.invoke(x);
                } catch (IllegalAccessException | InvocationTargetException e) {
                    e.printStackTrace();
                }
                return null;
            }).collect(Collectors.toList());
            /*查出所有顶级节点*/
            List<T> topLevel = list.stream().filter(x -> {
                try {
                    return !ids.contains(getParentId.invoke(x));
                } catch (IllegalAccessException | InvocationTargetException e) {
                    e.printStackTrace();
                }
                return false;
            }).collect(Collectors.toList());
    
            return recursion(topLevel, list);
        }
    
    
        /**
         * 递归装载
         *
         * @param superLevel 上级节点
         * @param list       数据集
         * @return
         */
        @SneakyThrows
        private <T> List<T> recursion(List<T> superLevel, List<T> list) {
            //获取泛型T的class
            Class<?> aClass = list.get(0).getClass();
    
            Field[] declaredFields = aClass.getDeclaredFields();
            //获取主键属性
            List<Field> idPropertyField = Arrays.stream(declaredFields).filter(x -> {
                TreeId annotation = x.getAnnotation(TreeId.class);
                return annotation != null;
            }).collect(Collectors.toList());
            if (idPropertyField.size() <= 0) {
                throw new RuntimeException("缺失@TreeId注解");
            }
            if (idPropertyField.size() > 1) {
                throw new RuntimeException("@TreeId注解只能存在一个");
            }
            //获取父节点属性
            List<Field> parentIdPropertyField = Arrays.stream(declaredFields).filter(x -> {
                TreeParentId annotation = x.getAnnotation(TreeParentId.class);
                return annotation != null;
            }).collect(Collectors.toList());
            if (parentIdPropertyField.size() <= 0) {
                throw new RuntimeException("缺失@ParentId注解");
            }
            if (parentIdPropertyField.size() > 1) {
                throw new RuntimeException("@ParentId注解只能存在一个");
            }
    
            //获取父节点属性
            List<Field> childrenPropertyField = Arrays.stream(declaredFields).filter(x -> {
                TreeChildren annotation = x.getAnnotation(TreeChildren.class);
                return annotation != null;
            }).collect(Collectors.toList());
            if (childrenPropertyField.size() <= 0) {
                throw new RuntimeException("缺失@TreeChildren注解");
            }
            if (childrenPropertyField.size() > 1) {
                throw new RuntimeException("@TreeChildren注解只能存在一个");
            }
    
            /*主键的属性名*/
            String idPropertyName = idPropertyField.get(0).getName();
            /*主键的get方法*/
            Method getId = aClass.getMethod("get" + StrUtil.upperFirst(idPropertyName));
    
            /*父节点的属性名*/
            String parentIdPropertyName = parentIdPropertyField.get(0).getName();
            /*父节点的get方法*/
            Method getParentId = aClass.getMethod("get" + StrUtil.upperFirst(parentIdPropertyName));
    
            /*子节点的属性名*/
            String childrenPropertyName = childrenPropertyField.get(0).getName();
            /*字节点的set方法*/
            Method setChildren = aClass.getMethod("set" + StrUtil.upperFirst(childrenPropertyName));
    
    
            for (T t : superLevel) {
                List<T> children = list.stream().filter(x -> {
                    try {
                        return getParentId.invoke(x).equals(getId.invoke(t));
                    } catch (IllegalAccessException | InvocationTargetException e) {
                        e.printStackTrace();
                    }
                    return false;
                }).collect(Collectors.toList());
                if (children.size() <= 0) {
                    continue;
                }
                List<T> recursion = recursion(children, list);
                setChildren.invoke(t, recursion);
            }
            return superLevel;
        }
    }

*  使用示例:
 *      import lombok.Data;
        
        import java.util.List;
        
        @Data
        public class My {
            @TreeId//在实体类的主键上打上该注解
            private String id;
        
            @TreeParentId//在实体类的父节点id上打上该注解
            private String parentId;
        
            private String name;
        
            @TreeChildren //在子集上打上该注解
            //@TableField(exist = false)//如果你用的是mybatis-plus则需要让框架忽略该字段
            private List<My> children;
        
            public My(String id, String parentId, String name) {
                this.id = id;
                this.parentId = parentId;
                this.name = name;
            }
        }
    
        public static void main(String[] args) {
                ArrayList<My> mies = new ArrayList<>();
                mies.add(new My("1", "-1", "a"));
                mies.add(new My("2", "-1", "aa"));
                mies.add(new My("3", "1", "b"));
                mies.add(new My("4", "1", "c"));
                mies.add(new My("5", "3", "d"));
                mies.add(new My("6", "5", "e"));
                mies.add(new My("7", "6", "f"));
                mies.add(new My("8", "2", "g"));
                mies.add(new My("9", "8", "h"));
                mies.add(new My("10", "9", "i"));
                List<My> mies1 = TreeUtil.treeOut(mies);
                System.out.println(mies1);
            }
    
    大功告成了,如果有问题请加博主V：sunziwen3366

[https_blog.csdn.net_wenxingchen_article_details_115749782_spm_1001.2014.3001.5501]: https://blog.csdn.net/wenxingchen/article/details/115749782?spm=1001.2014.3001.5501