简介
中介者模式（Mediator Pattern）是一种行为型模式。它限制对象之间的直接交互，它用一个中介对象来封装一系列的动作，以让对象之间进行交流。中介者使各个对象不需要显式地相互引用，从而使其耦合松散，而且可以独立地改变它们之间的交互。
当一些对象和其他对象紧密耦合以致难以对其进行修改时，或当组件因过于依赖其他组件而无法在不同应用中复用时，可使用中介者模式。
作用
- 用来降低多个对象和类之间的通信复杂性。
- 对象之间不再显式地相互引用，但可以独立地改变它们之间的交互，从而保持松耦合。
实现步骤
- 定义一个工具接口，供不同工具类来实现。建立多个具体工具类实现基础工具接口。
- 定义一个基础抽象类，里面聚合了工具接口，相当于桥接。
- 再重新定义一个新抽象类，继承自基础抽象类，并补充一些方法。
- 建立具体对象类继承新抽象类，调用桥接接口里的方法来实现功能。
UML
mediator-pattern.png
Java代码
中介者抽象接口
// RoomMediator.java 定义中介者接口或抽象类
public interface RoomMediator {
public void register(AbstractUser user);
public void sendTo(AbstractUser from, AbstractUser to, String message);
public void send(AbstractUser from, String message);
}
通用中介者
// GeneralRoom.java 中介者的具体实现类
public class GeneralRoom implements RoomMediator {
public List<AbstractUser> users = new ArrayList<AbstractUser>();
@Override
public void register(AbstractUser user) {
// 用户注册登记，追加用户列表
user.setRoomMediator(this);
users.add(user);
}
// 作为中介者通知给某个用户
@Override
public void sendTo(AbstractUser from, AbstractUser to, String message) {
System.out.println(
"GeneralRoom:sendTo() [from: " + from.getName() + " message: " + message + " to: " + to.getName() + " ]");
// 根据用户名称定向发送
to.recieve(from, message);
}
// 作为中介者通知给全体用户
@Override
public void send(AbstractUser from, String message) {
System.out.println("GeneralRoom:send() [from: " + from.getName() + " message: " + message + "]");
for (AbstractUser user : users) {
user.recieve(from, message);
}
}
}
抽象用户类
// AbstractUser.java 定义抽象用户类，聚合中介者
public abstract class AbstractUser {
private String name;
public RoomMediator roomMediator;
public AbstractUser(String name) {
this.name = name;
}
public void setRoomMediator(RoomMediator roomMediator) {
this.roomMediator = roomMediator;
}
public abstract void send(String message);
public abstract void sendTo(AbstractUser to, String message);
public abstract void recieve(AbstractUser from, String message);
public String getName() {
return this.name;
}
}
具体用户对象
// CommonUser.java 普通用户继承了抽象用户，实现了具体功能
public class CommonUser extends AbstractUser {
public CommonUser(String name) {
super(name);
}
@Override
public void send(String message) {
System.out.println("CommonUser:send() [user: " + this.getName() + " message:" + message + "]");
// 通过中介者来中转消息
this.roomMediator.send(this, message);
}
@Override
public void sendTo(AbstractUser to, String message) {
System.out.println("CommonUser:sendTo() [user: " + this.getName() + " message:" + message + " to: " + to.getName() + "]");
// 通过中介者来中转消息
this.roomMediator.sendTo(this, to, message);
}
@Override
public void recieve(AbstractUser from, String message) {
System.out.println("CommonUser:recieve() [user: " + this.getName() + " message: " + message + " from:" + from.getName() + "]");
}
}
// MemberUser.java 会员用户继承了抽象用户，实现了具体功能
public class MemberUser extends AbstractUser {
public MemberUser(String name) {
super(name);
}
@Override
public void send(String message) {
System.out.println("MemberUser:send() [user: " + this.getName() + " message:" + message + "]");
// 通过中介者来中转消息
this.roomMediator.send(this, message);
}
@Override
public void sendTo(AbstractUser to, String message) {
System.out
.println("MemberUser:sendTo() [user: " + this.getName() + " message:" + message + " to: " + to.getName() + "]");
// 通过中介者来中转消息
this.roomMediator.sendTo(this, to, message);
}
@Override
public void recieve(AbstractUser from, String message) {
System.out.println("MemberUser:recieve() [user: " + this.getName() + " message: " + message
+ " from user:" + from.getName() + "]");
}
}
测试调用
public class Test {
public static void start() {
/**
* 中介者模式用一个中介对象来封装一系列动作，让对象之间利用中介者来交流。
* 这里聊天室就是一个中介者，用户和用户之间的消息传递，全部依靠聊天室来完成。
* 先给聊天室注册用户，也给用户绑定上中介者，双方彼此持有关系。
* 中介者的成员之间的消息传递通过中介者来代理传达。
*/
// 声明一个聊天室
GeneralRoom generalRoom = new GeneralRoom();
// 给聊天室添加点不同的人
AbstractUser user1 = new CommonUser("user1");
generalRoom.register(user1);
CommonUser user2 = new CommonUser("user2");
generalRoom.register(user2);
MemberUser user3 = new MemberUser("user3");
generalRoom.register(user3);
// user1 发送给全体
user1.send("hi, I'm " + user1.getName() + ".");
// user2 发送给 user3
user2.sendTo(user3, "haha.");
}
public static void main(String[] args) {
System.out.println("test start:");
start();
}
}
Go代码
中介者抽象接口
// RoomMediator.go 定义中介者接口或抽象类
type RoomMediator interface {
Register(user AbstractUser)
SendTo(from AbstractUser, to AbstractUser, message string)
Send(from AbstractUser, message string)
}
通用中介者
// GeneralRoom.go 中介者的具体实现类
type GeneralRoom struct {
users []AbstractUser
}
func (g *GeneralRoom) Register(user AbstractUser) {
// 用户注册登记，追加用户列表
user.SetRoomMediator(g)
g.users = append(g.users, user)
}
// 作为中介者通知给某个用户
func (g *GeneralRoom) SendTo(from AbstractUser, to AbstractUser, message string) {
fmt.Println("GeneralRoom::SendTo() [from: " + from.GetName() + " message: " + message + " to: " + to.GetName() + "]")
// 定向发送给某个用户，名称唯一
to.Recieve(from, message)
}
// 作为中介者通知给全体用户
func (g *GeneralRoom) Send(from AbstractUser, message string) {
fmt.Println("GeneralRoom::Send() [from: " + from.GetName() + " message: " + message + "] ")
for _, user := range g.users {
user.Recieve(from, message)
}
}
抽象用户类
// AbstractUser.go 定义抽象用户类，聚合中介者
type AbstractUser interface {
SetRoomMediator(roomMediator RoomMediator)
Send(message string)
SendTo(to AbstractUser, message string)
Recieve(from AbstractUser, message string)
GetName() string
}
具体用户对象
// CommonUser.go 普通用户继承了抽象用户，实现了具体功能
type CommonUser struct {
Name string
roomMediator RoomMediator
}
func (c *CommonUser) SetRoomMediator(roomMediator RoomMediator) {
c.roomMediator = roomMediator
}
func (c *CommonUser) Send(message string) {
fmt.Println("CommonUser:Send() [user: " + c.GetName() + " message: " + message + "]")
// 通过中介者来中转消息
c.roomMediator.Send(c, message)
}
func (c *CommonUser) SendTo(to AbstractUser, message string) {
fmt.Println("CommonUser:SendTo() [user: " + c.GetName() + " message: " + message + "]")
// 通过中介者来中转消息
c.roomMediator.SendTo(c, to, message)
}
func (c *CommonUser) Recieve(from AbstractUser, message string) {
fmt.Println("CommonUser:Recieve() [user: " + c.GetName() + " message: " + message + " from: " + from.GetName() + "]")
}
func (c *CommonUser) SetName(name string) {
c.Name = name
}
func (c *CommonUser) GetName() string {
return c.Name
}
// MemberUser.go 会员用户继承了抽象用户，实现了具体功能
type MemberUser struct {
// Name首字母大写以便跨模块访问
Name string
roomMediator RoomMediator
}
func (c *MemberUser) SetRoomMediator(roomMediator RoomMediator) {
c.roomMediator = roomMediator
}
func (c *MemberUser) Send(message string) {
fmt.Println("MemberUser:Send() [user: " + c.GetName() + " message: " + message + "]")
// 通过中介者来中转消息
c.roomMediator.Send(c, message)
}
func (c *MemberUser) SendTo(to AbstractUser, message string) {
fmt.Println("MemberUser:SendTo() [user: " + c.GetName() + " message: " + message + "]")
// 通过中介者来中转消息
c.roomMediator.SendTo(c, to, message)
}
func (c *MemberUser) Recieve(from AbstractUser, message string) {
fmt.Println("MemberUser:Recieve() [user: " + c.GetName() + " message: " + message + " from: " + from.GetName() + "]")
}
func (c *MemberUser) SetName(name string) {
c.Name = name
}
func (c *MemberUser) GetName() string {
return c.Name
}
测试调用
func main() {
fmt.Println("test start:")
/**
* 中介者模式用一个中介对象来封装一系列动作，让对象之间利用中介者来交流。
* 这里聊天室就是一个中介者，用户和用户之间的消息传递，全部依靠聊天室来完成。
* 先给聊天室注册用户，也给用户绑定上中介者，双方彼此持有关系。
* 中介者的成员之间的消息传递通过中介者来代理传达。
*/
// 声明一个聊天室
var generalRoom = new(src.GeneralRoom)
// 给聊天室添加点不同的人
var user1 = &src.CommonUser{
Name: "user1",
}
generalRoom.Register(user1)
var user2 = &src.CommonUser{
Name: "user2",
}
generalRoom.Register(user2)
var user3 = &src.MemberUser{
Name: "user3",
}
generalRoom.Register(user3)
// user1 发送给全体
user1.Send("hi, I'm " + user1.GetName() + ".")
// user2 发送给 user3
user2.SendTo(user3, "haha.")
}
C语言简版
#include <stdio.h>
/**
* 中介者模式是一种行为型设计模式，它可以用来减少类之间的直接依赖关系，
* 将对象之间的通信封装到一个中介者对象中，从而使得各个对象之间的关系更加松散。
* 在中介者模式中，对象之间不再直接相互交互，而是通过中介者来中转消息。
*/
typedef struct Colleague Colleague;
typedef struct Mediator Mediator;
// 定义抽象交互对象类
struct Colleague
{
int id;
struct Mediator *mediator;
void (*send)(struct Colleague *sender, char *message);
void (*send_to)(struct Colleague *sender, Colleague *receiver, char *message);
void (*receive)(struct Colleague *receiver, Colleague *sender, char *message);
};
// 定义中介者类
struct Mediator
{
struct Colleague **colleagues;
int colleagues_length;
void (*send)(Colleague *sender, char *message);
void (*send_to)(Colleague *sender, Colleague *receiver, char *message);
};
// 交互对象发送消息
void colleague_send(Colleague *sender, char *message)
{
printf("\r\n colleague_send() [sender->id=%d message=%s]", sender->id, message);
Mediator *mediator = sender->mediator;
// 由中介者代为转发消息给全体接收者
mediator->send(sender, message);
}
// 交互对象发送消息
void colleague_send_to(Colleague *sender, Colleague *receiver, char *message)
{
printf("\r\n colleague_send_to() [sender->id=%d receiver->id=%d message=%s]", sender->id, receiver->id, message);
Mediator *mediator = sender->mediator;
// 由中介者代为转发消息给指定接收者
mediator->send_to(sender, receiver, message);
}
// 对象接收消息
void colleague_receive(Colleague *receiver, Colleague *sender, char *message)
{
printf("\r\n colleague_receive() [receiver->id=%d send->id=%d message=%s]", receiver->id, sender->id, message);
}
// 中介者发送消息
void mediator_send(Colleague *sender, char *message)
{
printf("\r\n mediator_send() [sender->id=%d message=%s]", sender->id, message);
Colleague *receiver;
for (int i = 0; i < sender->mediator->colleagues_length; i++)
{
// 中介者通知全体接收者
receiver = sender->mediator->colleagues[i];
receiver->receive(receiver, sender, message);
}
}
// 中介者发送消息
void mediator_send_to(Colleague *sender, Colleague *receiver, char *message)
{
// 中介者通知指定接收者
printf("\r\n mediator_send_to() [sender->id=%d receiver->id=%d message=%s]", sender->id, receiver->id, message);
receiver->receive(receiver, sender, message);
}
// 初始化交互对象类
void colleague_constructor(Colleague *self, int id)
{
self->id = id;
self->send = colleague_send;
self->send_to = colleague_send_to;
self->receive = colleague_receive;
}
// 初始化中介者类
void mediator_constructor(Mediator *self, Colleague **colleagues, int colleagues_length)
{
self->colleagues = colleagues;
self->colleagues_length = colleagues_length;
// 给每个对象绑定中介者
for (int i = 0; i < self->colleagues_length; i++)
{
self->colleagues[i]->mediator = self;
}
self->send = &mediator_send;
self->send_to = &mediator_send_to;
}
// test
int main()
{
// 初始化具体交互对象a，分别绑定相关函数
Colleague colleague_a;
colleague_constructor(&colleague_a, 1);
// 初始化具体交互对象b，分别绑定相关函数
Colleague colleague_b;
colleague_constructor(&colleague_b, 2);
// 定义交互对象数组
Colleague *colleagues[] = {&colleague_a, &colleague_b};
int colleagues_length = sizeof(colleagues) / sizeof(colleagues[0]);
printf("colleagues_length=%d", colleagues_length);
// 初始化中介者类，绑定交互对象
Mediator mediator;
mediator_constructor(&mediator, colleagues, colleagues_length);
// 交互类发送消息
colleague_a.send(&colleague_a, "Hi, all! I'm a.");
printf("\r\n ==== \r\n");
colleague_a.send_to(&colleague_a, &colleague_b, "Hello, colleague_b. I am a!");
printf("\r\n ==== \r\n");
colleague_b.send_to(&colleague_b, &colleague_a, "Hi, colleague_a! I'm b.");
return 0;
}
更多语言版本
不同语言实现设计模式：https://github.com/microwind/design-pattern
