一、概述
組合模式,又叫部分整體模式,屬於結構型模式,它創建了對象組的屬性結構,將對象組合成樹狀結構以表示“整體-部分”的層次關係。組合模式可以不提供父對象的管理方法,但是組合模式必須在合適的地方提供子對象的管理方法,例如:add(),remove()以及getChild()等。組合模式的實現根據所實現接口的區別分爲安全式和透明式。
二、角色
抽象構件(Component):定義參加組合對象的共有方法和屬性,可以定義一些默認的行爲或屬性
樹枝構件(Composite):樹枝對象,用於存儲子部件,在Component接口中實現子部件的相關操作,比如增加,刪除
葉子構件(Leaf):葉子對象,其下再也沒有其他的分支,也就是遍歷的最小單位
三、組合模式
1.安全式組合模式
安全模式的組合模式要求管理聚集的方法只出現在樹枝構件類中,而不出現樹葉構件類中
1) 抽象構件
public interface OrganizationComponent {
void print();
}
2) 樹枝構件
// University就是Composite
public class University implements OrganizationComponent {
private String name;
// 存放的是College
private List<OrganizationComponent> organizationComponents = new ArrayList<>();
public University(String name) {
this.name = name;
}
public void addChild(OrganizationComponent organizationComponent) {
organizationComponents.add(organizationComponent);
}
public void removeChild(OrganizationComponent organizationComponent) {
organizationComponents.remove(organizationComponent);
}
// 輸入University所包含的College
@Override
public void print() {
System.out.println("- - - -" + name + "- - - -");
// 遍歷organizationComponents
for (OrganizationComponent organizationComponent : organizationComponents) {
organizationComponent.print();
}
}
}
public class College implements OrganizationComponent {
private String name;
// 存放的是Department
private List<OrganizationComponent> organizationComponents = new ArrayList<>();
public College(String name) {
this.name = name;
}
public void addChild(OrganizationComponent organizationComponent) {
organizationComponents.add(organizationComponent);
}
public void removeChild(OrganizationComponent organizationComponent) {
organizationComponents.remove(organizationComponent);
}
// 輸入College所包含的Department
@Override
public void print() {
System.out.println("- - - -" + name + "- - - -");
// 遍歷organizationComponents
for (OrganizationComponent organizationComponent : organizationComponents) {
organizationComponent.print();
}
}
}
3) 葉子構件
public class Department implements OrganizationComponent {
private String name;
public Department(String name) {
this.name = name;
}
public void print() {
System.out.println(name);
}
}
4) 使用
@Test
public void testSafeComposite() {
// 創建學校
University university = new University("清華大學");
// 創建學院
College computerCollege = new College("計算機學院");
College infoEngineerCollege = new College("信息工程學院");
// 創建系
computerCollege.addChild(new Department("軟件工程"));
computerCollege.addChild(new Department("網絡工程"));
computerCollege.addChild(new Department("計算機科學與技術"));
infoEngineerCollege.addChild(new Department("通信工程"));
infoEngineerCollege.addChild(new Department("信息工程"));
university.addChild(computerCollege);
university.addChild(infoEngineerCollege);
university.print();
}
2.透明式組合模式
透明式的組合模式要求所有的具體構件類,不論數構件還是樹葉構件,均符合一個固定接口
1) 抽象構件
public abstract class OrganizationComponent {
private String name;
public OrganizationComponent(String name) {
this.name = name;
}
protected void removeChild(OrganizationComponent organizationComponent) {
// 默認實現
throw new UnsupportedOperationException();
}
protected void addChild(OrganizationComponent organizationComponent) {
// 默認實現
throw new UnsupportedOperationException();
}
protected abstract void print();
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
2) 樹枝構件
public class University extends OrganizationComponent {
// 存放的是College
private List<OrganizationComponent> organizationComponents = new ArrayList<>();
// 構造器
public University(String name) {
super(name);
}
@Override
protected void addChild(OrganizationComponent organizationComponent) {
organizationComponents.add(organizationComponent);
}
@Override
protected void removeChild(OrganizationComponent organizationComponent) {
organizationComponents.remove(organizationComponent);
}
// 輸入University所包含的College
@Override
protected void print() {
System.out.println("- - - -" + getName() + "- - - -");
// 遍歷organizationComponents
for (OrganizationComponent organizationComponent : organizationComponents) {
organizationComponent.print();
}
}
}
public class College extends OrganizationComponent {
// 存放的是Department
private List<OrganizationComponent> organizationComponents = new ArrayList<>();
// 構造器
public College(String name) {
super(name);
}
@Override
protected void addChild(OrganizationComponent organizationComponent) {
organizationComponents.add(organizationComponent);
}
@Override
protected void removeChild(OrganizationComponent organizationComponent) {
organizationComponents.remove(organizationComponent);
}
// 輸入College所包含的Department
@Override
protected void print() {
System.out.println("- - - -" + getName() + "- - - -");
// 遍歷organizationComponents
for (OrganizationComponent organizationComponent : organizationComponents) {
organizationComponent.print();
}
}
}
3) 葉子構件
public class Department extends OrganizationComponent {
public Department(String name) {
super(name);
}
// add,remove就不用寫了,因爲它是葉子節點
@Override
protected void print() {
System.out.println(getName());
}
}
4) 使用
@Test
public void testComposite() {
// 創建學校
OrganizationComponent university = new University("清華大學");
// 創建學院
OrganizationComponent computerCollege = new College("計算機學院");
OrganizationComponent infoEngineerCollege = new College("信息工程學院");
// 創建系
computerCollege.addChild(new Department("軟件工程"));
computerCollege.addChild(new Department("網絡工程"));
computerCollege.addChild(new Department("計算機科學與技術"));
infoEngineerCollege.addChild(new Department("通信工程"));
infoEngineerCollege.addChild(new Department("信息工程"));
university.addChild(computerCollege);
university.addChild(infoEngineerCollege);
university.print();
}
四、安全式與透明式
安全式組合模式:從客戶端使用組合模式上看是否安全,如果是安全的,那麼就不會發生誤操作的可能,能訪問的方法都是支持的
透明式組合模式:從客戶端使用組合模式上,是否需要區分到底是“樹枝對象”還是“樹葉對象”。如果是透明的,那就不用區分,對於客戶而言,都是Component對象,具體的類型對於客戶端而言是透明的
對於組合模式而言,在安全性和透明性上,會更看重透明性,畢竟組合模式的目的是:讓客戶端不再區分操作的是樹枝對象還是樹葉對象,而是以一個統一的方式來操作
在使用組合模式的時候,建議多采用透明式的實現方式