设计模式笔记----观察者模式

一，问题引入

天气预报项目需求

1.气象站可以将每天测量到的温度，湿度，气压等以公告的形式发布出去

2.需要设计开放型api，便于其他第三方，也能接入气象站获取数据

3.提供温度，气压和湿度的接口

4.测量数据更新时，要能实时的传给第三方

二，普通方案

WeatherData：天气数据

package 设计模式.观察者模式.普通方案;
//包含一个website对象，一旦数据有更改，就主动调用website对象的update
public class WeatherData {
    private float temperature;
    private float pressure;
    private float humidity;
    private Website date;
    public WeatherData(Website date){
        this.date=date;
    }
    public float getTemperature() {
        return temperature;
    }
    public void setTemperature(float temperature) {
        this.temperature = temperature;
    }
    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 void dataChange(){
        date.update(getTemperature(),getPressure(),getHumidity());
    }
    public void setDate(float temperature,float pressure,float humidity){
        this.temperature=temperature;
        this.pressure=pressure;
        this.humidity=humidity;
        //推送最新的信息
        dataChange();
    }
}

Website：需要数据的第三方

package 设计模式.观察者模式.普通方案;
//显示当前天气情况
public class Website {
    private float temperature;
    private float pressure;
    private float humidity;
    //更新天气情况
    public void update(float temperature,float pressure,float humidity){
        this.temperature=temperature;
        this.pressure=pressure;
        this.humidity=humidity;
        display();
    }
    public void display(){
        System.out.println("温度是"+temperature);
        System.out.println("气压是"+pressure);
        System.out.println("湿度是"+humidity);
    }
}

Client：

package 设计模式.观察者模式.普通方案;

public class Client {
    public static void main(String []args){
        Website website=new Website();
        WeatherData weatherData=new WeatherData(website);
        weatherData.setDate(100,100,100);
        weatherData.setDate(40,40,40);
    }
}

四，使用观察者模式解决

Observer：观察者接口

package 设计模式.观察者模式.Improve;

public interface Observer {
    public void update(float temperature,float pressure,float humidity);
}

CurrentCondition：具体观察者

package 设计模式.观察者模式.Improve;

public class CurentConditons implements Observer{
    private float temperature;
    private float pressure;
    private float humidity;
    @Override
    public void update(float temperature, float pressure, float humidity) {
        this.temperature=temperature;
        this.pressure=pressure;
        this.humidity=humidity;
        display();
    }
    public void display(){
        System.out.println("温度:"+temperature);
        System.out.println("气压:"+pressure);
        System.out.println("湿度:"+humidity);
    }
}

Subject：数据接口

package 设计模式.观察者模式.Improve;

public interface Sunject {
    public void registObserver(Observer o);
    public void removeObserver(Observer o);
    public void notifyObservers();
}

WeatherData：天气数据，使用一个数据集合存储具体观察者

package 设计模式.观察者模式.Improve;

import java.util.ArrayList;
import java.util.List;

public class WeatherData implements  Sunject {
    private float temperature;
    private float pressure;
    private float humidity;
    List<Observer> list = new ArrayList<Observer>();
    public void setDate(float temperature,float pressure,float humidity){
        this.temperature=temperature;
        this.pressure=pressure;
        this.humidity=humidity;
        notifyObservers();
    }
    //添加一个观察者
    @Override
    public void registObserver(Observer o) {
        list.add(o);
    }

    //移除一个观察者
    @Override
    public void removeObserver(Observer o) {
        if (list.contains(o))
            list.remove(o);
    }

    //遍历所有观察者
    @Override
    public void notifyObservers(){
        for(Observer i:list){
            dateChange(i);
        }
    }
    public void dateChange(Observer o){
        o.update(temperature,pressure,humidity);
    }
}

Client：使用

package 设计模式.观察者模式.Improve;

public class Client{
    public static void main(String []args){
        WeatherData weatherData=new WeatherData();
        weatherData.registObserver(new CurentConditons());
        weatherData.registObserver(new CurentConditons());
        //
        weatherData.setDate(100,100,100);
    }
}