Internet气象站项目:
提供温度、气压和湿度的接口
测量数据更新时需时时通知给第三方 需要设计开放型API,便于其他第三方公司也能接入气象站获取数据
WeatherData类
一个通常的设计方案
代码演示:
WeatherData类
package com.java.hexter.internetweather;
public class WeatherData {
private float mTemperatrue;
private float mPressure;
private float mHumidity;
private CurrentConditions mCurrentConditions;
public WeatherData(CurrentConditions mCurrentConditions)
{
this. mCurrentConditions= mCurrentConditions;
}
public float getTemperature()
{
return mTemperatrue;
}
public float getPressure()
{
return mPressure;
}
public float getHumidity()
{
return mHumidity;
}
public void dataChange()
{
mCurrentConditions.update(getTemperature(), getPressure(), getHumidity());
}
public void setData(float mTemperature,float mPressure,float mHumidity)
{
this.mTemperatrue=mTemperature;
this.mPressure=mPressure;
this.mHumidity=mHumidity;
dataChange();
}
}
代表第三方的类
package com.java.hexter.internetweather;
public class CurrentConditions {
private float mTemperature;
private float mPressure;
private float mHumidity;
public void update(float mTemperature,float mPressure,float mHumidity)
{
this.mTemperature=mTemperature;
this.mPressure=mPressure;
this.mHumidity=mHumidity;
display();
}
public void display()
{
System.out.println("***Today mTemperature: "+mTemperature+"***");
System.out.println("***Today mPressure: "+mPressure+"***");
System.out.println("***Today mHumidity: "+mHumidity+"***");
}
}
有些问题
1)其他第三方公司接入气象站获取数据的问题
2)无法在运行时动态的添加第三方
观察者模式就像定牛奶业务
1)奶站,Subject
2)用户,Observer
Subject:登记注册、移除和通知
Observer:接收输入
观察者模式: 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
用观察者模式设计重新设计的方案
代码演示:
package com.java.hexter.internetweather.observer;
public interface Subject {
public void registerObserver(Observer o);
public void removeObserver(Observer o);
public void notifyObservers();
}
package com.java.hexter.internetweather.observer;
public interface Observer {
public void update(float mTemperatrue,float mPressure,float mHumidity);
}
package com.java.hexter.internetweather.mode;
import java.util.ArrayList;
import com.java.hexter.internetweather.observer.Observer;
import com.java.hexter.internetweather.observer.Subject;
public class WeatherDataSt implements Subject{
private float mTemperatrue;
private float mPressure;
private float mHumidity;
private ArrayList<Observer> mObservers;
public WeatherDataSt()
{
mObservers=new ArrayList<Observer>();
}
public float getTemperature()
{
return mTemperatrue;
}
public float getPressure()
{
return mPressure;
}
public float getHumidity()
{
return mHumidity;
}
public void dataChange()
{
notifyObservers();
}
public void setData(float mTemperatrue,float mPressure,float mHumidity)
{
this.mTemperatrue=mTemperatrue;
this.mPressure=mPressure;
this.mHumidity=mHumidity;
dataChange();
}
@Override
public void registerObserver(Observer o) {
// TODO Auto-generated method stub
mObservers.add(o);
}
@Override
public void removeObserver(Observer o) {
// TODO Auto-generated method stub
if(mObservers.contains(o))
{mObservers.remove(o);}
}
@Override
public void notifyObservers() {
// TODO Auto-generated method stub
for(int i=0,len=mObservers.size();i<len;i++)
{
mObservers.get(i).update(getTemperature(), getPressure(), getHumidity());
}
}
}
package com.java.hexter.internetweather.mode;
import com.java.hexter.internetweather.observer.Observer;
public class CurrentConditions implements Observer {//可以有多个子类代表多个第三方
private float mTemperatrue;
private float mPressure;
private float mHumidity;
@Override
public void update(float mTemperatrue, float mPressure, float mHumidity) {
// TODO Auto-generated method stub
this.mHumidity = mHumidity;
this.mPressure = mPressure;
this.mTemperatrue = mTemperatrue;
display();
}
public void display() {
System.out.println("***Today mTemperatrue:" + mTemperatrue + "***");
System.out.println("***Today mPressure:" + mPressure + "***");
System.out.println("***Today mHumidity:" + mHumidity + "***");
}
}
Java内置的观察者 Observable Observer
用Java内置观察者重新设计该项目
内置观察者的注意点 Observable是类而不是接口
代码如下:
package com.java.hexter.internetweather.jv;
import java.util.Observable;
public class WeatherData extends Observable{
private float mTemperatrue;
private float mPressure;
private float mHumidity;
public float getTemperature()
{
return mTemperatrue;
}
public float getPressure()
{
return mPressure;
}
public float getHumidity()
{
return mHumidity;
}
public void dataChange()
{
this.setChanged();
this.notifyObservers(new Data(getTemperature(),getPressure(),getHumidity()));
}
public void setData(float mTemperatrue,float mPressure,float mHumidity)
{
this.mTemperatrue=mTemperatrue;
this.mPressure=mPressure;
this.mHumidity=mHumidity;
dataChange();
}
public class Data
{
public float mTemperatrue;
public float mPressure;
public float mHumidity;
public Data(float mTemperatrue,float mPressure,float mHumidity)
{
this.mTemperatrue=mTemperatrue;
this.mPressure=mPressure;
this.mHumidity=mHumidity;
}
}
}
package com.java.hexter.internetweather.jv;
import java.util.Observable;
import java.util.Observer;
import com.java.hexter.internetweather.jv.WeatherData.Data;
public class CurrentConditions implements Observer {
private float mTemperatrue;
private float mPressure;
private float mHumidity;
@Override
public void update(Observable arg0, Object arg1) {
// TODO Auto-generated method stub
this.mTemperatrue=((Data)(arg1)).mTemperatrue;
this.mPressure=((Data)(arg1)).mPressure;
this.mHumidity=((Data)(arg1)).mHumidity;
display();
}
public void display()
{
System.out.println("***Today mTemperatrue:" +mTemperatrue+"***");
System.out.println("***Today mPressure:" +mPressure+"***");
System.out.println("***Today mHumidity:" +mHumidity+"***");
}
}