java 实现用户部门的上级树结构

假设您有以下表结构：

- 用户表 user(id, name, department_id)
- 部门表 department(id, name, parent_id)

其中，`department` 表的 `parent_id` 字段表示父级部门的 id，如果该字段为 `NULL`，则表示该部门为顶级部门。

现在，假设您已经获取了当前用户的 `id`，您可以使用以下 Java 代码查询该用户所在的部门树结构：

import java.sql.*;
import java.util.*;

public class UserDepartmentTree {
    private static final String URL = "jdbc:mysql://localhost:3306/test";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "123456";

    public static void main(String[] args) {
        try (Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
             PreparedStatement stmt = conn.prepareStatement(
                "WITH RECURSIVE department_tree(id, name, parent_id, depth) AS (" +
                "  SELECT id, name, parent_id, 0" +
                "  FROM department" +
                "  WHERE id = (SELECT department_id FROM user WHERE id = ?)" +
                "  UNION ALL" +
                "  SELECT d.id, d.name, d.parent_id, dt.depth + 1" +
                "  FROM department d" +
                "  JOIN department_tree dt ON d.id = dt.parent_id" +
                ")" +
                "SELECT id, name, parent_id, depth" +
                " FROM department_tree" +
                " ORDER BY depth")) {
            stmt.setInt(1, 1); // 假设当前用户的 id 为 1
            ResultSet rs = stmt.executeQuery();

            // 构建部门树结构
            Map<Integer, Department> map = new HashMap<>();
            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                int parentId = rs.getInt("parent_id");
                int depth = rs.getInt("depth");
                Department department = new Department(id, name, parentId, depth);
                map.put(id, department);
                if (parentId != 0) {
                    map.get(parentId).addChild(department);
                }
            }

            // 打印部门树结构
            Department root = map.get(1); // 假设当前用户所在的部门为顶级部门
            printDepartmentTree(root, 0);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private static void printDepartmentTree(Department root, int level) {
        for (int i = 0; i < level; i++) {
            System.out.print("  ");
        }
        System.out.println(root.getName());
        for (Department child : root.getChildren()) {
            printDepartmentTree(child, level + 1);
        }
    }

    private static class Department {
        private int id;
        private String name;
        private int parentId;
        private int depth;
        private List<Department> children = new ArrayList<>();

        public Department(int id, String name, int parentId, int depth) {
            this.id = id;
            this.name = name;
            this.parentId = parentId;
            this.depth = depth;
        }

        public int getId() {
            return id;
        }

        public String getName() {
            return name;
        }

        public int getParentId() {
            return parentId;
        }

        public int getDepth() {
            return depth;
        }

        public List<Department> getChildren() {
            return children;
        }

        public void addChild(Department child) {
            children.add(child);
        }
    }
}

这里使用了递归查询语句（`WITH RECURSIVE`）查询部门树结构，并将查询结果转换为一个部门树结构，最终按照深度打印出部门树结构。

需要注意的是，上述代码中的 `1` 需要替换为当前用户的实际 `id` 值。同时，您需要根据您使用的数据库类型和 JDBC 驱动程序来执行 SQL 查询，并将查询结果转换为您所需的数据结构。