观察者模式
2020-10-25 本文已影响0人
乙腾
case
image.png
非设计模式code
SimpleWeatherData
package com.pl.designMode.observer.simple;
/**
* <p>
*
* @Description: TODO
* </p>
* @ClassName SimpleWeatherData
* @Author pl
* @Date 2020/10/25
* @Version V1.0.0
*/
public class SimpleWeatherData {
private float temperatrue;
private float pressure;
private float humidity;
//第三方
private SimpleBaidu simpleBaidu;
public void setData(float temperatrue, float pressure, float humidity) {
this.temperatrue = temperatrue;
this.pressure = pressure;
this.humidity = humidity;
dataChange();
}
public void dataChange(){
simpleBaidu.update(getTemperatrue(),getPressure(),getHumidity());
}
public float getTemperatrue() {
return temperatrue;
}
public void setTemperatrue(float temperatrue) {
this.temperatrue = temperatrue;
}
public float getPressure() {
return pressure;
}
public void setPressure(float pressure) {
this.pressure = pressure;
}
public float getHumidity() {
return humidity;
}
public void setHumidity(float humidity) {
this.humidity = humidity;
}
public SimpleBaidu getSimpleBaidu() {
return simpleBaidu;
}
public void setSimpleBaidu(SimpleBaidu simpleBaidu) {
this.simpleBaidu = simpleBaidu;
}
}
SimpleBaidu
package com.pl.designMode.observer.simple;
/**
* <p>
*
* @Description: TODO
* </p>
* @ClassName SimpleBaidu
* @Author pl
* @Date 2020/10/25
* @Version V1.0.0
*/
public class SimpleBaidu {
// 温度，气压，湿度
private float temperature;
private float pressure;
private float humidity;
//更新 天气情况，是由 WeatherData 来调用，我使用推送模式
public void update(float temperature, float pressure, float humidity) {
this.temperature = temperature;
this.pressure = pressure;
this.humidity = humidity;
display();
}
//显示
public void display() {
System.out.println("***Today mTemperature: " + temperature + "***");
System.out.println("***Today mPressure: " + pressure + "***");
System.out.println("***Today mHumidity: " + humidity + "***");
}
}
SimpleClient
package com.pl.designMode.observer.simple;
/**
* <p>
*
* @Description: TODO
* </p>
* @ClassName SimpleClient
* @Author pl
* @Date 2020/10/25
* @Version V1.0.0
*/
public class SimpleClient {
public static void main(String[] args) {
SimpleWeatherData simpleWeatherData = new SimpleWeatherData();
SimpleBaidu simpleBaidu = new SimpleBaidu();
simpleWeatherData.setSimpleBaidu(simpleBaidu);
simpleWeatherData.setData(22,21,11);
}
}
优缺点
优点：
线性思维，通过每次setData通知第三方
缺点：
违反ocp原则，即对扩展开放，对修改关闭。当新加入第三方时候，SimpleWeatherData需要跟着改，没有扩展性。
Observer code
Observer
package com.pl.designMode.observer.oberserverDesign;
/**
* <p>
*
* @Description: TODO
* </p>
* @ClassName Observer
* @Author pl
* @Date 2020/10/25
* @Version V1.0.0
*/
public interface Observer {
void update(float temperature, float pressure, float humidity);
}
Subject
package com.pl.designMode.observer.oberserverDesign;
/**
* @Auther: pl
* @Date: 2020/10/25 11:00
* @Description:
*/
public interface Subject {
void registerObserver(Observer o);
void removeObserver(Observer o);
void notifyObservers();
}
WeatherData
package com.pl.designMode.observer.oberserverDesign;
import java.util.ArrayList;
import java.util.List;
/**
* <p>
*
* @Description: TODO
* </p>
* @ClassName WeatherData
* @Author pl
* @Date 2020/10/25
* @Version V1.0.0
*/
public class WeatherData implements Subject {
private float temperatrue;
private float pressure;
private float humidity;
//第三方
private List<Observer> observerList;
/**
* 空参构造 为成员observerList变量赋值
*
* @param
* @return
* @exception
* @author silenter
* @date 2020/10/25 11:17
*/
public WeatherData() {
observerList = new ArrayList<>();
}
/**
* 数据变更
*
* @param temperatrue
* @param pressure
* @param humidity
* @return void
* @exception
* @author silenter
* @date 2020/10/25 11:18
*/
public void setData(float temperatrue, float pressure, float humidity) {
this.temperatrue = temperatrue;
this.pressure = pressure;
this.humidity = humidity;
notifyObservers();
}
/**
*Observer 注册
*
* @param o
* @return void
* @exception
* @author silenter
* @date 2020/10/25 11:13
*/
@Override
public void registerObserver(Observer o) {
observerList.add(o);
}
/**
* 移除观察者
*
* @param o
* @return void
* @exception
* @author silenter
* @date 2020/10/25 11:14
*/
@Override
public void removeObserver(Observer o) {
observerList.remove(o);
}
/**
* 通知观察者
*
* @param
* @return void
* @exception
* @author silenter
* @date 2020/10/25 11:14
*/
@Override
public void notifyObservers() {
observerList.forEach((data)->{
dataChange(data);
});
}
public void dataChange(Observer o){
o.update(getTemperatrue(),getPressure(),getHumidity());
}
public float getTemperatrue() {
return temperatrue;
}
public float getPressure() {
return pressure;
}
public float getHumidity() {
return humidity;
}
public List<Observer> getObserverList() {
return observerList;
}
}
CurrentConditions
package com.pl.designMode.observer.oberserverDesign;
public class CurrentConditions implements Observer {
// 温度，气压，湿度
private float temperature;
private float pressure;
private float humidity;
// 更新 天气情况，是由 WeatherData 来调用，我使用推送模式
@Override
public void update(float temperature, float pressure, float humidity) {
this.temperature = temperature;
this.pressure = pressure;
this.humidity = humidity;
display();
}
// 显示
public void display() {
System.out.println("***Today mTemperature: " + temperature + "***");
System.out.println("***Today mPressure: " + pressure + "***");
System.out.println("***Today mHumidity: " + humidity + "***");
}
}
BaiduSite
package com.pl.designMode.observer.oberserverDesign;
public class BaiduSite implements Observer {
// 温度，气压，湿度
private float temperature;
private float pressure;
private float humidity;
// 更新 天气情况，是由 WeatherData 来调用，我使用推送模式
@Override
public void update(float temperature, float pressure, float humidity) {
this.temperature = temperature;
this.pressure = pressure;
this.humidity = humidity;
display();
}
// 显示
public void display() {
System.out.println("===百度网站====");
System.out.println("***百度网站 气温 : " + temperature + "***");
System.out.println("***百度网站 气压: " + pressure + "***");
System.out.println("***百度网站 湿度: " + humidity + "***");
}
}
Client
package com.pl.designMode.observer.oberserverDesign;
public class Client {
public static void main(String[] args) {
// TODO Auto-generated method stub
//创建一个WeatherData
WeatherData weatherData = new WeatherData();
//创建观察者
CurrentConditions currentConditions = new CurrentConditions();
BaiduSite baiduSite = new BaiduSite();
//注册到weatherData
weatherData.registerObserver(currentConditions);
weatherData.registerObserver(baiduSite);
//测试
System.out.println("通知各个注册的观察者, 看看信息");
weatherData.setData(10f, 100f, 30.3f);
weatherData.removeObserver(currentConditions);
//测试
System.out.println();
System.out.println("通知各个注册的观察者, 看看信息");
weatherData.setData(10f, 100f, 30.3f);
}
}
观察者模式介绍
对象之间多对一依赖的一种设计方案，被依赖的对象为 Subject，依赖的对象为 Observer，Subject通知 Observer 变化,比如这里的奶站是 Subject，是 1 的一方。用户时 Observer，是多的一方。
使用场景
适用于通知的场景，一个数据变更，需要通知多个监听者。
代码实现
观察者模式首先通过代码声明了subject,obersever，都是借口，在管理观察者的类中，通过指定obersever类型的接口来管理oberserver集合，这样只要第三方实现了oberserver接口，就可以放到观察者集合中管理，其实核心依旧是面向接口开发，类的多态。
类图
image.png
23种设计模式
设计模式是jdk提供的一些应对不同业务场景的策略。
