举个在Maven项目中实现菜单管理的父子级表格展现的例子，即前后端代码

这是一个简单的Maven项目中实现菜单管理的父子级表格展现的示例，包括前后端代码。

1. 后端代码（使用Spring Boot框架）

Menu实体类

@Entity
@Table(name = "menu")
public class Menu {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String name;

    private String url;

    @Column(name = "parent_id")
    private Long parentId;

    @OneToMany(mappedBy = "parentMenu", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Menu> subMenus = new ArrayList<>();

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "parent_id", insertable = false, updatable = false)
    private Menu parentMenu;

    // getter and setter
}

MenuRepository接口

public interface MenuRepository extends JpaRepository<Menu, Long> {

    List<Menu> findByParentId(Long parentId);
}

MenuService实现类

@Service
public class MenuServiceImpl implements MenuService {

    private final MenuRepository menuRepository;

    public MenuServiceImpl(MenuRepository menuRepository) {
        this.menuRepository = menuRepository;
    }

    @Override
    public List<Menu> getAllMenus() {
        List<Menu> rootMenus = menuRepository.findByParentId(null);
        setSubMenus(rootMenus);
        return rootMenus;
    }

    private void setSubMenus(List<Menu> menus) {
        for (Menu menu : menus) {
            menu.setSubMenus(menuRepository.findByParentId(menu.getId()));
            setSubMenus(menu.getSubMenus());
        }
    }
}

MenuController类

@RestController
@RequestMapping("/menu")
public class MenuController {

    private final MenuService menuService;

    public MenuController(MenuService menuService) {
        this.menuService = menuService;
    }

    @GetMapping("/all")
    public List<Menu> getAllMenus() {
        return menuService.getAllMenus();
    }
}

2. 前端代码（使用Vue.js框架）

Menu组件

<template>
  <div>
    <el-table :data="menus" style="width: 100%">
      <el-table-column prop="name" label="名称"></el-table-column>
      <el-table-column prop="url" label="URL"></el-table-column>
      <el-table-column label="操作">
        <template slot-scope="scope">
          <el-button type="primary" size="small" @click="handleEdit(scope.row)">编辑</el-button>
          <el-button type="danger" size="small" @click="handleDelete(scope.row)">删除</el-button>
        </template>
      </el-table-column>
    </el-table>
    <el-dialog :visible.sync="dialogVisible">
      <el-form :model="form" label-width="100px">
        <el-form-item label="名称">
          <el-input v-model="form.name"></el-input>
        </el-form-item>
        <el-form-item label="URL">
          <el-input v-model="form.url"></el-input>
        </el-form-item>
      </el-form>
      <div slot="footer" class="dialog-footer">
        <el-button @click="dialogVisible = false">取 消</el-button>
        <el-button type="primary" @click="handleSubmit">确 定</el-button>
      </div>
    </el-dialog>
  </div>
</template>

<script>
  export default {
    data() {
      return {
        menus: [],
        form: {
          id: '',
          name: '',
          url: '',
          parentId: ''
        },
        dialogVisible: false
      }
    },
    created() {
      this.getMenus();
    },
    methods: {
      getMenus() {
        this.$http.get('/menu/all').then(response => {
          this.menus = response.data;
        });
      },
      handleEdit(menu) {
        this.form = Object.assign({}, menu);
        this.dialogVisible = true;
      },
      handleDelete(menu) {
        this.$confirm('确认删除该菜单?', '提示', {
          confirmButtonText: '确定',
          cancelButtonText: '取消',
          type: 'warning'
        }).then(() => {
          this.$http.delete('/menu/' + menu.id).then(() => {
            this.getMenus();
          });
        });
      },
      handleSubmit() {
        let method = this.form.id ? 'put' : 'post';
        this.$http[method]('/menu', this.form).then(() => {
          this.dialogVisible = false;
          this.getMenus();
        });
      }
    }
  }
</script>

以上代码只是一个简单的示例，实际项目中需要根据具体需求进行调整和完善。