Java 实现数据树形结构代码

// 准备使用到的实体类
@Getter
@Setter
@ToString
public class DeptLevelDto extends SysDept {

    private List<DeptLevelDto> deptList = Lists.newArrayList();

    public static DeptLevelDto adapt(SysDept dept) {
        DeptLevelDto dto = new DeptLevelDto();
        BeanUtils.copyProperties(dept, dto);
        return dto;
    }
}

// 级别 工具类

public class LevelUtil {

    public final static String SEPARATOR = ".";

    public final static String ROOT = "0";

    // 0
    // 0.1
    // 0.1.2
    // 0.1.3
    // 0.4
    public static String calculateLevel(String parentLevel, int parentId) {
        if (StringUtils.isBlank(parentLevel)) {
            return ROOT;
        } else {
            return StringUtils.join(parentLevel, SEPARATOR, parentId);
        }
    }
}

// 开始代码 
public List<DeptLevelDto> deptTree() {
    List<SysDept> deptList = sysDeptMapper.getAllDept();

    List<DeptLevelDto> dtoList = Lists.newArrayList();
    for (SysDept dept : deptList) {
        DeptLevelDto dto = DeptLevelDto.adapt(dept);
        dtoList.add(dto);
    }
    return deptListToTree(dtoList);
}

public List<DeptLevelDto> deptListToTree(List<DeptLevelDto> deptLevelList) {
    if (CollectionUtils.isEmpty(deptLevelList)) {
        return Lists.newArrayList();
    }
    // level -> [dept1, dept2, ...] Map<String, List<Object>>
    Multimap<String, DeptLevelDto> levelDeptMap = ArrayListMultimap.create();
    List<DeptLevelDto> rootList = Lists.newArrayList();

    for (DeptLevelDto dto : deptLevelList) {
        levelDeptMap.put(dto.getLevel(), dto);
        if (LevelUtil.ROOT.equals(dto.getLevel())) {
            rootList.add(dto);
        }
    }
    // 按照seq从小到大排序
    Collections.sort(rootList, new Comparator<DeptLevelDto>() {
        public int compare(DeptLevelDto o1, DeptLevelDto o2) {
            return o1.getSeq() - o2.getSeq();
        }
    });
    // 递归生成树
    transformDeptTree(rootList, LevelUtil.ROOT, levelDeptMap);
    return rootList;
}

// level:0, 0, all 0->0.1,0.2
// level:0.1
// level:0.2
public void transformDeptTree(List<DeptLevelDto> deptLevelList, String level, Multimap<String, DeptLevelDto> levelDeptMap) {
    for (int i = 0; i < deptLevelList.size(); i++) {
        // 遍历该层的每个元素
        DeptLevelDto deptLevelDto = deptLevelList.get(i);
        // 处理当前层级的数据
        String nextLevel = LevelUtil.calculateLevel(level, deptLevelDto.getId());
        // 处理下一层
        List<DeptLevelDto> tempDeptList = (List<DeptLevelDto>) levelDeptMap.get(nextLevel);
        if (CollectionUtils.isNotEmpty(tempDeptList)) {
            // 排序
            Collections.sort(tempDeptList, deptSeqComparator);
            // 设置下一层部门
            deptLevelDto.setDeptList(tempDeptList);
            // 进入到下一层处理
            transformDeptTree(tempDeptList, nextLevel, levelDeptMap);
        }
    }
}

public Comparator<DeptLevelDto> deptSeqComparator = new Comparator<DeptLevelDto>() {
    public int compare(DeptLevelDto o1, DeptLevelDto o2) {
        return o1.getSeq() - o2.getSeq();
    }
};

public Comparator<AclModuleLevelDto> aclModuleSeqComparator = new Comparator<AclModuleLevelDto>() {
    public int compare(AclModuleLevelDto o1, AclModuleLevelDto o2) {
        return o1.getSeq() - o2.getSeq();
    }
};

public Comparator<AclDto> aclSeqComparator = new Comparator<AclDto>() {
    public int compare(AclDto o1, AclDto o2) {
        return o1.getSeq() - o2.getSeq();
    }
};

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