设计模式-组合模式

Deschen2025-10-17 13:50

文章目录

研究了很久，我发现组合模式，跟装饰者模式有异曲同工之处。就是在原来的功能基础上，装饰了保存子节点的集合

一、详解

  • 概念：抽象类组件 与一个包含子组件 的子组件类 ，构建树形结构
  • 主要用途：
    • 在不改变现有对象结构的情况下，动态地给一个对象增加新的功能
    • 需要添加一些附加的功能，但是使用继承会导致类的数量增加，且继承层次复杂，而装饰者可以聚合新功能的类，添加新功能
  • 代码：原有的类/接口（抽象类组件）、包含子组件的子组件类（装饰了保存子节点功能）
  • PS: 为什么我不直接把子组件类抽象出来？是因为组合模式本来就是用于组合树结构，没有其他意思，就不要抽象出来

二、代码

  • 源码：https://gitee.com/deschen/designPattern-study

  • 以部门树为例

  • 部门类

    java 复制代码 
    public class Dept implements IDept {

    private Long id;

    private String name;

    private Integer level;

    private Long parentId;

    public Dept() {
    }

    public Dept(Long id, String name, Integer level, Long parentId) {
        this.id = id;
        this.name = name;
        this.level = level;
        this.parentId = parentId;
    }

    @Override
    public Long getId() {
        return id;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public Integer getLevel() {
        return level;
    }

    @Override
    public Long getParentId() {
        return parentId;
    }

    @Override
    public Boolean isRoot() {
        return parentId == -1;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setLevel(Integer level) {
        this.level = level;
    }

    public void setParentId(Long parentId) {
        this.parentId = parentId;
    }

    @Override
    public String toString() {
        return "Dept{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", level='" + level + '\'' +
                ", parentId=" + parentId +
                '}';
    }
}

  • 部门的抽象类 - 提取部门需要展示的属性，同时方便以后部门类整改不受影响，保证可维护性

    java 复制代码 
    public interface IDept {

    Long getId();

    String getName();

    Integer getLevel();

    Long getParentId();

    Boolean isRoot();
}

  • 包含部门的部门树

    java 复制代码 
    public class DeptNode implements IDept {

    private IDept dept;

    private List<DeptNode> children;

    public DeptNode(IDept dept) {
        this.dept = dept;
        this.children = new ArrayList<>();
    }

    @Override
    public Long getId() {
        return dept.getId();
    }

    @Override
    public String getName() {
        return dept.getName();
    }

    @Override
    public Integer getLevel() {
        return dept.getLevel();
    }

    @Override
    public Long getParentId() {
        return dept.getParentId();
    }

    @Override
    public Boolean isRoot() {
        return dept.isRoot();
    }

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

    public void setChildren(List<DeptNode> children) {
        this.children = children;
    }

    public void addNode(DeptNode node) {
        this.children.add(node);
    }

    public String deptInfo() {
        return "Dept{" +
                "id=" + getId() +
                ", name='" + getName() + '\'' +
                ", level='" + getLevel() + '\'' +
                ", parentId=" + getParentId() +
                '}';
    }
}

  • 部门树生成器

    java 复制代码 
    public class DeptNodeBuilder {

    public Map<Long, DeptNode> nodeMap = new HashMap<>();

    /**
     * 通过增加内存空间来构建树 - 遍历
     * @param depts 部门集合
     * @return
     */
    public DeptNode buildByIncrMem(List<Dept> depts) {
        for (Dept dept : depts) {
            nodeMap.put(dept.getId(), new DeptNode(dept));
        }

        DeptNode root = null;

        for (DeptNode node : nodeMap.values()) {
            if (!node.isRoot()) {
                DeptNode parent = nodeMap.get(node.getParentId());
                parent.addNode(node);
            }else {
                root = node;
            }
        }

        return root;
    }

    /**
     * 通过增加栈来构建树 - 递归
     *
     * @param depts 部门集合
   * @return
     */
    public DeptNode buildByIncrStack(List<Dept> depts) {
        List<DeptNode> nodes = new ArrayList<>();
        DeptNode root = null;
        for (Dept dept : depts) {
            DeptNode node = new DeptNode(dept);
            if (dept.isRoot()) {
                root = node;
            }
            nodes.add(node);
        }

        root.setChildren(children(nodes, root));

        return root;
    }

    private List<DeptNode> children(List<DeptNode> nodes, DeptNode parent) {
        List<DeptNode> children = nodes.stream()
                .filter(node -> node.getParentId().equals(parent.getId()))
                .peek(node -> {
                    node.setChildren(children(nodes, node));
                }).collect(Collectors.toList());
        return children;
    }


}

  • 测试用例

    java 复制代码 
    public class Demo {

    public static ObjectMapper objectMapper = new ObjectMapper();

    public static void main(String[] args) throws JsonProcessingException {
        List<Dept> depts = new ArrayList<>();
        Dept root = new Dept(0L, "0", 0, -1L);
        depts.add(root);
        Long id = 0L;
        for (Long i = 0L; i <= 3L; i++) {
            for (Long j = 0L; j < 3L; j++) {
                id++;
                Dept child = new Dept(id, id.toString(), j.intValue(), i);
                depts.add(child);
            }
        }

        DeptNodeBuilder builder = new DeptNodeBuilder();
        DeptNode rootNode = builder.buildByIncrMem(depts);

        System.out.println(objectMapper.writeValueAsString(rootNode));

        DeptNode rootNode1 = builder.buildByIncrStack(depts);
        System.out.println(objectMapper.writeValueAsString(rootNode1));

    }
}

// 输出结果
{"children":[{"children":[{"children":[],"name":"4","id":4,"root":false,"level":0,"parentId":1},{"children":[],"name":"5","id":5,"root":false,"level":1,"parentId":1},{"children":[],"name":"6","id":6,"root":false,"level":2,"parentId":1}],"name":"1","id":1,"root":false,"level":0,"parentId":0},{"children":[{"children":[],"name":"7","id":7,"root":false,"level":0,"parentId":2},{"children":[],"name":"8","id":8,"root":false,"level":1,"parentId":2},{"children":[],"name":"9","id":9,"root":false,"level":2,"parentId":2}],"name":"2","id":2,"root":false,"level":1,"parentId":0},{"children":[{"children":[],"name":"10","id":10,"root":false,"level":0,"parentId":3},{"children":[],"name":"11","id":11,"root":false,"level":1,"parentId":3},{"children":[],"name":"12","id":12,"root":false,"level":2,"parentId":3}],"name":"3","id":3,"root":false,"level":2,"parentId":0}],"name":"0","id":0,"root":true,"level":0,"parentId":-1}
{"children":[{"children":[{"children":[],"name":"4","id":4,"root":false,"level":0,"parentId":1},{"children":[],"name":"5","id":5,"root":false,"level":1,"parentId":1},{"children":[],"name":"6","id":6,"root":false,"level":2,"parentId":1}],"name":"1","id":1,"root":false,"level":0,"parentId":0},{"children":[{"children":[],"name":"7","id":7,"root":false,"level":0,"parentId":2},{"children":[],"name":"8","id":8,"root":false,"level":1,"parentId":2},{"children":[],"name":"9","id":9,"root":false,"level":2,"parentId":2}],"name":"2","id":2,"root":false,"level":1,"parentId":0},{"children":[{"children":[],"name":"10","id":10,"root":false,"level":0,"parentId":3},{"children":[],"name":"11","id":11,"root":false,"level":1,"parentId":3},{"children":[],"name":"12","id":12,"root":false,"level":2,"parentId":3}],"name":"3","id":3,"root":false,"level":2,"parentId":0}],"name":"0","id":0,"root":true,"level":0,"parentId":-1}

三、优化

上面的是针对业务（部门）抽象，组合形成部门树。但是菜单、文件等这些层级属性的实体，难道要重新copy一份在写吗？

能不能把他们的共性抽取出来呢？

部门、菜单、文件共性：标识、父标识、名称等节点属性

部门树、菜单树、文件树共性：包含自身，即节点集合

  • 组合模式概念：抽象类组件和包含子组件的子组件类

    • 第一版：抽象类组件（部门）、子组件（部门树）
    • 第二版：抽象类组件（节点属性）、抽象子组件（节点树）、部门类（抽象类的子类）、部门树（抽象子组件的子类）

  • 代码

    • 抽象类组件（节点属性）

      java 复制代码 
      public interface NodeEntity {

    /**
     * 节点ID，节点唯一标识
     * @return
     */
    Long getId();

    /**
     * 节点名称
     * @return
     */
    String getName();

    /**
     * 父节点ID，体现出层级关系
     * @return
     */
    Long getParentId();

    /**
     * 节点顺序，可以实所有节点的顺序，也可以是同级下的节点顺序。如果为空，默认不排序
     * @return
     */
    Integer getSort();

    /**
     * 是否是根节点
     * @return
     */
    Boolean isRoot();
}

    • 抽象子组件类（节点树）

      java 复制代码 
      public abstract class Node<E extends NodeEntity, N extends Node> implements NodeEntity {

    protected E entity;

    protected List<N> children;

    public Node() {
    }

    public Node(E entity) {
        this.entity = entity;
        this.children = new ArrayList<>();
    }

    @Override
    public Long getId() {
        return entity.getId();
    }

    @Override
    public String getName() {
        return entity.getName();
    }

    @Override
    public Long getParentId() {
        return entity.getParentId();
    }

    @Override
    public Integer getSort() {
        return null == entity.getSort()? 0: entity.getSort();
    }

    @Override
    public Boolean isRoot() {
        return entity.isRoot();
    }

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

    public void setChildren(List<N> children) {
        this.children = children;
    }

    public void addNode(N node) {
        this.children.add(node);
    }
}

    • 部门类（节点的子类，添加业务属性）

      java 复制代码 
      public class Dept implements NodeEntity {

    private Long id;

    private String name;

    private Long parentId;

    private Integer sort;

    /**
     * 新增属性：层级
     */
    private Integer level;

    public Dept(Long id, String name, Long parentId, Integer sort, Integer level) {
        this.id = id;
        this.name = name;
        this.parentId = parentId;
        this.sort = sort;
        this.level = level;
    }

    @Override
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    @Override
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public Long getParentId() {
        return parentId;
    }

    public void setParentId(Long parentId) {
        this.parentId = parentId;
    }

    @Override
    public Integer getSort() {
        return sort;
    }

    @Override
    public Boolean isRoot() {
        return parentId == -1;
    }

    public void setSort(Integer sort) {
        this.sort = sort;
    }

    public Integer getLevel() {
        return level;
    }

    public void setLevel(Integer level) {
        this.level = level;
    }
}

    • 部门树（节点树的子类，添加业务属性）

      java 复制代码 
      public class DeptNode extends Node<Dept, DeptNode> {

    public DeptNode(Dept dept) {
        super(dept);
    }

    /**
     * 新增属性：层级
     * @return
     */
    public Integer getLevel() {
        return entity.getLevel();
    }
}

    • 节点树生成器

      java 复制代码 
      public abstract class TreeNodeBuilder<E extends NodeEntity, N extends Node> {

    protected NodeSortComparator comparator = new NodeSortComparator();

    /**
     * 通过增加内存空间来构建树 - 遍历
     *
     * @param entities 节点实体集合
     * @return
     */
    public N buildByIncrMem(List<E> entities) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
        Map<Long, N> nodeMap = new HashMap<>();

        // 排序
        Collections.sort(entities, comparator);

        List<N> nodes = new ArrayList<>();
        N root = null;

        for (E entity : entities) {
            N node = createNode(entity);
            nodes.add(node);
            nodeMap.put(node.getId(), node);
            if (entity.isRoot()) {
                root = node;
            }
        }

        for (N node : nodeMap.values()) {
            if (!node.isRoot()) {
                N parent = nodeMap.get(node.getParentId());
                parent.addNode(node);
            } else {
                root = node;
            }
        }

        return root;
    }

    protected abstract N createNode(E entity);

    /**
     * 通过增加栈来构建树 - 递归
     *
     * @param entities 节点实体集合
     * @return
     */
    public N buildByIncrStack(List<E> entities) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
        List<N> nodes = new ArrayList<>();
        N root = null;

        for (E entity : entities) {
            N node = createNode(entity);
            nodes.add(node);
            if (entity.isRoot()) {
                root = node;
            }
        }

        root.setChildren(children(nodes, root));

        return (N) root;
    }

    private List<N> children(List<N> nodes, N parent) {
        List<N> children = nodes.stream()
                .filter(node -> node.getParentId().equals(parent.getId()))
                .peek(node -> {
                    node.setChildren(children(nodes, node));
                })
                .sorted(comparator)
                .collect(Collectors.toList());
        return children;
    }


}

/**
 * 节点排序器
 */
class NodeSortComparator implements Comparator<NodeEntity> {

    @Override
    public int compare(NodeEntity o1, NodeEntity o2) {
        return o1.getSort().compareTo(o2.getSort());
    }
}

    • 部门树（节点树生成器，覆盖或者新增功能）

      java 复制代码 
      public class DeptNodeBuilder extends TreeNodeBuilder<Dept, DeptNode> {

    @Override
    protected DeptNode createNode(Dept dept) {
        return new DeptNode(dept);
    }
}

    • 测试用例

      java 复制代码 
      public class Demo {

    public static ObjectMapper objectMapper = new ObjectMapper();

    public static void main(String[] args) throws JsonProcessingException, InvocationTargetException, NoSuchMethodException, InstantiationException, IllegalAccessException {
        List<Dept> depts = new ArrayList<>();
        Dept root = new Dept(0L, "0", -1L, 0, 0);
        depts.add(root);
        Long id = 0L;
        for (Long i = 0L; i <= 3L; i++) {
            for (Long j = 0L; j < 3L; j++) {
                id++;
                Integer level = 1;
                if (i != 0L) {
                    level = 2;
                }
                Dept child = new Dept(id, id.toString(), i, j.intValue(), level);
                depts.add(child);
            }
        }

        DeptNodeBuilder builder = new DeptNodeBuilder();
        DeptNode rootNode = builder.buildByIncrMem(depts);

        System.out.println(objectMapper.writeValueAsString(rootNode));

        DeptNode rootNode1 = builder.buildByIncrStack(depts);
        System.out.println(objectMapper.writeValueAsString(rootNode1));

    }
}

// 输出结果
{"children":[{"children":[{"children":[],"level":2,"name":"4","id":4,"parentId":1,"sort":0,"root":false},{"children":[],"level":2,"name":"5","id":5,"parentId":1,"sort":1,"root":false},{"children":[],"level":2,"name":"6","id":6,"parentId":1,"sort":2,"root":false}],"level":1,"name":"1","id":1,"parentId":0,"sort":0,"root":false},{"children":[{"children":[],"level":2,"name":"7","id":7,"parentId":2,"sort":0,"root":false},{"children":[],"level":2,"name":"8","id":8,"parentId":2,"sort":1,"root":false},{"children":[],"level":2,"name":"9","id":9,"parentId":2,"sort":2,"root":false}],"level":1,"name":"2","id":2,"parentId":0,"sort":1,"root":false},{"children":[{"children":[],"level":2,"name":"10","id":10,"parentId":3,"sort":0,"root":false},{"children":[],"level":2,"name":"11","id":11,"parentId":3,"sort":1,"root":false},{"children":[],"level":2,"name":"12","id":12,"parentId":3,"sort":2,"root":false}],"level":1,"name":"3","id":3,"parentId":0,"sort":2,"root":false}],"level":0,"name":"0","id":0,"parentId":-1,"sort":0,"root":true}
{"children":[{"children":[{"children":[],"level":2,"name":"4","id":4,"parentId":1,"sort":0,"root":false},{"children":[],"level":2,"name":"5","id":5,"parentId":1,"sort":1,"root":false},{"children":[],"level":2,"name":"6","id":6,"parentId":1,"sort":2,"root":false}],"level":1,"name":"1","id":1,"parentId":0,"sort":0,"root":false},{"children":[{"children":[],"level":2,"name":"7","id":7,"parentId":2,"sort":0,"root":false},{"children":[],"level":2,"name":"8","id":8,"parentId":2,"sort":1,"root":false},{"children":[],"level":2,"name":"9","id":9,"parentId":2,"sort":2,"root":false}],"level":1,"name":"2","id":2,"parentId":0,"sort":1,"root":false},{"children":[{"children":[],"level":2,"name":"10","id":10,"parentId":3,"sort":0,"root":false},{"children":[],"level":2,"name":"11","id":11,"parentId":3,"sort":1,"root":false},{"children":[],"level":2,"name":"12","id":12,"parentId":3,"sort":2,"root":false}],"level":1,"name":"3","id":3,"parentId":0,"sort":2,"root":false}],"level":0,"name":"0","id":0,"parentId":-1,"sort":0,"root":true}

  • 可见，有新的业务要生成树形结构，先后要继承/实现节点属性（NodeEntity） 、节点树（Node）、**节点生成器（TreeNodeBuilder）**就可以了，如果要定制化，就直接在其基础上修改

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