设计模式入门--发布订阅模式

本文主要是介绍设计模式入门--发布订阅模式，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

概念

首先说明一下，发布-订阅模式并不等同于观察者模式，这两者是有区别的。举例说明，用户直接向出版社订阅杂志，出版社直接把杂志发送给订阅杂志的用户，这种场景就是观察者模式。而发布-订阅模式则不同，出版社和用户并不直接接触，用户是向邮局订阅杂志，出版社向邮局发布杂志后，邮局再向用户派送杂志。也就是说，发布-订阅模式是有一个中转调度中心的。如下图：

上图发布订阅模式进行抽象如下图，借图一用：

发布订阅模式角色

发布者：消息或者说主题的生产者。
订阅者：订阅消息或主题的消费者。
调度中心/消息管理器：生产者发布消息与消费者订阅消息的中转站，调度作用。
主题：也称消息，生产者生产与消费者使用的内容。

代码实现

案例场景：拓展《设计模式入门–观察者模式》案例二场景(资讯网站每天给注册用户推送新闻)为：很多自媒体作者向资讯网站投内容，文章被采用后，适时给注册用户推送文章。作者是消息发布者，注册用户是订阅者，调度中心是网站平台，主题则为内容（文章、广告、活动）。
思路：其实就是实现上述四个角色，这里以最简单的方式实现。
发布者：能够向平台提交内容
订阅者：能够从平台获取推送的内容、然后读内容
内容：文章、广告、活动，就是一个封装的实体类
调度中心：能够存储发布者提交的内容，能够添加、删除订阅者，能够推送消息给订阅者

发布者->

抽象发布者基类

package learn.publishsubscribe.example;/*** 抽象发布者* Created by chao.du on 2018/2/1.*/
public interface BaseAuthor<T> {/*** 发布消息（作者向网站提交文章）* @param contentHelper  消息管理器，订阅器*/void pushlishContent(ContentHelper contentHelper,T content);}

具体发布者

package learn.publishsubscribe.example;/*** 具体发布者1，作者1* Created by chao.du on 2018/2/1.*/
public class AuthorA<T extends BaseContent> implements BaseAuthor<T> {private String name;public void pushlishContent(ContentHelper contentHelper,T content) {contentHelper.publishContentToQueue(content);}public AuthorA(String name) {this.name = name;}public String getName() {return name;}public void setName(String name) {this.name = name;}
}
/*** 具体发布者2，作者2* Created by chao.du on 2018/2/1.*/
public class AuthorB<T extends BaseContent> implements BaseAuthor<T> {private String name;public AuthorB(String name) {this.name = name;}public String getName() {return name;}public void setName(String name) {this.name = name;}public void pushlishContent(ContentHelper contentHelper,T content) {contentHelper.publishContentToQueue(content);}}

订阅者->

抽象订阅者基类

package learn.publishsubscribe.example;/*** 抽象订阅者* Created by chao.du on 2018/2/1.*/
public abstract class BaseReader {/*** 消息*/protected BaseContent content;/*** 读者名字*/protected String name;public BaseReader(String name) {this.name = name;}/*** 订阅消息（注册用户向网站订阅文章）* @param contentHelper  消息管理器，订阅器*/void subscribeContent(ContentHelper contentHelper){contentHelper.addReader(this);}/*** 收到内容处理器推送的消息（注册用户接手某作者的创作内容）* @param content 文章*/void receiveContent(BaseContent content){this.content=content;String title=null;if(content instanceof Article){title=((Article) content).getTitle();}else if(content instanceof Advertisement){title=((Advertisement) content).getTitle();}else{title=((Activity) content).getTitle();}System.out.println(this.name+"：收到来自【"+this.content.getWriteBy()+"】的"+this.content.getContentType()+"【"+title+"】");this.readContent(this.content);}/*** 收到消息，进行后续逻辑（读消息）* @param content*/abstract void  readContent(BaseContent content);
}

具体订阅者

package learn.publishsubscribe.example;/*** 具体订阅者，注册者1* Created by chao.du on 2018/2/1.*/
public class Reader1 extends BaseReader {public Reader1(String name) {super(name);}public void readContent(BaseContent content) {System.out.println(this.name+"----这篇文章我读了1111");}
}package learn.publishsubscribe.example;/*** 具体订阅者，注册者2* Created by chao.du on 2018/2/1.*/
public class Reader2 extends BaseReader {public Reader2(String name) {super(name);}public void readContent(BaseContent content) {System.out.println(this.name+"----这篇文章我读了2222");}
}package learn.publishsubscribe.example;/*** 具体订阅者，注册者3* Created by chao.du on 2018/2/1.*/
public class Reader3 extends BaseReader {public Reader3(String name) {super(name);}public void readContent(BaseContent content) {System.out.println(this.name+"----这篇文章我读了3333");}
}

消息->

消息基类

package learn.publishsubscribe.example;import java.util.Date;/*** 消息类，主题，内容类型：文章、广告、活动等* Created by chao.du on 2018/2/1.*/
public abstract class BaseContent {protected String contentType;protected Date createTime;protected String writeBy;public BaseContent() {this.createTime=new Date();}public BaseContent(String contentType) {this.contentType=contentType;this.createTime=new Date();}public BaseContent(String contentType, String writeBy) {this.contentType=contentType;this.writeBy=writeBy;this.createTime=new Date();}public String getContentType() {return contentType;}public Date getCreateTime() {return createTime;}public String getWriteBy() {return writeBy;}public void setWriteBy(String writeBy) {this.writeBy = writeBy;}
}

具体消息类

package learn.publishsubscribe.example;/*** 内容--文章类* Created by chao.du on 2018/2/1.*/
public class Article extends BaseContent {/*** 标题*/private String title;/*** 标签*/private String tag;/*** 简介*/private String descrition;/*** 正文*/private String content;public Article() {super("文章");}public Article(String writeBy, String title, String tag, String descrition, String content) {super("文章",writeBy);this.title = title;this.tag = tag;this.descrition = descrition;this.content = content;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getTag() {return tag;}public void setTag(String tag) {this.tag = tag;}public String getDescrition() {return descrition;}public void setDescrition(String descrition) {this.descrition = descrition;}public String getContent() {return content;}public void setContent(String content) {this.content = content;}}package learn.publishsubscribe.example;/*** 内容--广告类* Created by chao.du on 2018/2/1.*/
public class Advertisement extends BaseContent {/*** 广告标题*/private String title;/*** 广告banner地址*/private String banner;/*** 广告描述*/private String descrtion;public Advertisement() {super("广告");}public Advertisement(String writeBy, String title, String banner, String descrtion) {super("广告",writeBy);this.title = title;this.banner = banner;this.descrtion = descrtion;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getBanner() {return banner;}public void setBanner(String banner) {this.banner = banner;}public String getDescrtion() {return descrtion;}public void setDescrtion(String descrtion) {this.descrtion = descrtion;}
}package learn.publishsubscribe.example;import java.util.Date;/*** 内容--活动类* Created by chao.du on 2018/2/1.*/
public class Activity extends BaseContent {/*** 活动标题*/private String title;/*** 活动介绍*/private String content;/*** 活动时间*/private Date date;public Activity() {super("活动");}public Activity(String title, String content, Date date) {super("活动");this.title = title;this.content = content;this.date = date;}public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getContent() {return content;}public void setContent(String content) {this.content = content;}public Date getDate() {return date;}public void setDate(Date date) {this.date = date;}
}

调度中心->

package learn.publishsubscribe.example;import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;/*** 消息管理器，主题调度中心，网站文章处理器* Created by chao.du on 2018/2/1.*/
public class ContentHelper{/*** 内容调度器注册订阅内容的读者（网站注册者）容器*/private List<BaseReader> readerList=new ArrayList<BaseReader>();/*** 发布者发布消息的消息存储队列*/private Queue<BaseContent> queue = new LinkedList();public ContentHelper() {}public ContentHelper(List<BaseReader> readerList) {this.readerList = readerList;}/*** 向消息队列添加消息（供发布者发布信息调用使用）* @param content*/public void publishContentToQueue(BaseContent content){this.queue.offer(content);for(BaseReader reader:readerList){reader.receiveContent(content);}}/*** 向订阅者推送消息（供订阅者获取内容处理器推送的消息，订阅者调用）* @return*/public void pushContentFromQueue(){for (BaseReader reader:readerList){reader.receiveContent(this.queue.poll());}}/*** 添加订阅者*/public void addReader(BaseReader reader){this.readerList.add(reader);}/*** 删除订阅者*/public void removeReader(BaseReader reader){this.removeReader(reader);}
}

客户端->

package learn.publishsubscribe.example;/*** 场景：很多作者向资讯平台提交消息内容（文章、广告、活动），资讯平台向平台注册用户推送消息内容* Created by chao.du on 2018/2/2.*/
public class Client {public static void main(String[] args) {//内容处理器ContentHelper contentHelper=new ContentHelper();//订阅人，订阅消息new Reader1("小明").subscribeContent(contentHelper);new Reader2("小张").subscribeContent(contentHelper);new Reader3("小花").subscribeContent(contentHelper);//发布人，发布消息new AuthorA("美食博主").pushlishContent(contentHelper,new Article("美食博主","红烧肉绝佳菜谱","红烧肉","很好的红烧肉菜谱","步骤一、二、三"));new AuthorB("广告人").pushlishContent(contentHelper,new Advertisement("广告人","营销黄金法则","http://www.baidu.com/1.jpg","学会营销。。。。。"));}
}