《研磨设计模式》chap20 享元模式 Flyweight (4)总结

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1. 不共享的外部状态

输入数据为：
张三,人员列表,查看,1
李四,人员列表,查看,1
李四,操作薪资数据,2

" 操作薪资数据"包括"薪资数据,查看",“薪资数据,修改” 在这里插入图片描述

public class UnsharedConcreteFlyweight implements Flyweight{//记录每个组合对象所包含的子组件 private List<Flyweight> list = new ArrayList<Flyweight>(); public void add(Flyweight f) {list.add(f);} public boolean match(String securityEntity, String permit) {for(Flyweight f : list){//递归调用if(f.match(securityEntity, permit)){return true;}}return false;}
}public class AuthorizationFlyweight implements Flyweight{... public void add(Flyweight f) {throw new UnsupportedOperationException("对象不支持这个功能");}
}public class SecurityMgr {...//从数据库中获取某人所拥有的权限 private Collection<Flyweight> queryByUser(String user){Collection<Flyweight> col = new ArrayList<Flyweight>(); for(String s : TestDB.colDB){String ss[] = s.split(",");if(ss[0].equals(user)){Flyweight fm = null;if(ss[3].equals("2")){//表示是组合fm = new UnsharedConcreteFlyweight();//获取需要组合的数据String tempSs[] = TestDB.mapDB.get(ss[1]);for(String tempS : tempSs){Flyweight tempFm = FlyweightFactory.getInstance().getFlyweight(tempS);//把这个对象加入到组合对象中fm.add(tempFm);}}else{fm = FlyweightFactory.getInstance().getFlyweight(ss[1]+","+ss[2]);}col.add(fm);}}return col;}	
}public class TestDB { ...static{//通过静态块来填充模拟的数据，增加一个标识来表明是否组合授权数据colDB.add("张三,人员列表,查看,1");colDB.add("李四,人员列表,查看,1");colDB.add("李四,操作薪资数据,,2"); mapDB.put("操作薪资数据",new String[]{"薪资数据,查看","薪资数据,修改"});//增加更多的授权数据for(int i=0;i<3;i++){colDB.add("张三"+i+",人员列表,查看,1");}}	
}

2. 对享元对象的管理：引用计数、时间有效


public class CacheConfModel{//缓存开始计时的开始时间  private long beginTime;//缓存对象存放的持续时间，其实是最长不被使用的时间 private double durableTime;//缓存对象需要被永久存储，也就是不需要从缓存中删除 private boolean forever;  
}public class FlyweightFactory { private FlyweightFactory(){//启动清除缓存值的线程Thread t = new ClearCache();t.start();} //缓存多个flyweight对象 private Map<String,Flyweight> fsMap = new HashMap<String,Flyweight>();//用来缓存被共享对象的缓存配置，key值和上面map的一样 private  Map<String,CacheConfModel> cacheConfMap = new HashMap<String,CacheConfModel>();//用来记录缓存对象被引用的次数，key值和上面map的一样 private  Map<String,Integer> countMap = new HashMap<String,Integer>();//默认保存6秒钟  private final  long DURABLE_TIME = 6*1000L; //获取某个享元被使用的次数 public synchronized int getUseTimes(String key){Integer count = countMap.get(key);if(count==null){count = 0;}return count;}//获取key对应的享元对象 public synchronized Flyweight getFlyweight(String key) {Flyweight f = fsMap.get(key);//换一个更简单点的写法if(f==null){f = new AuthorizationFlyweight(key);fsMap.put(key,f);//同时设置引用计数countMap.put(key, 1);//同时设置缓存配置数据CacheConfModel cm = new CacheConfModel();cm.setBeginTime(System.currentTimeMillis());cm.setForever(false);cm.setDurableTime(DURABLE_TIME);cacheConfMap.put(key, cm);}else{//表示还在使用，那么应该重新设置缓存配置CacheConfModel cm = cacheConfMap.get(key);cm.setBeginTime(System.currentTimeMillis());//设置回去this.cacheConfMap.put(key, cm);//同时计数加1Integer count = countMap.get(key);count++;countMap.put(key, count);}return f;}//删除key对应的享元对象 private synchronized void removeFlyweight(String key){this.fsMap.remove(key);this.cacheConfMap.remove(key);this.countMap.remove(key);}//维护清除缓存的线程，内部使用 private  class ClearCache extends Thread{public void run(){while(true){Set<String> tempSet = new HashSet<String>();Set<String> set = cacheConfMap.keySet();for(String key : set){CacheConfModel ccm = cacheConfMap.get(key);//比较是否需要清除if((System.currentTimeMillis()-ccm.getBeginTime())>= ccm.getDurableTime()){//可以清除，先记录下来tempSet.add(key);}}//真正清除for(String key : tempSet){FlyweightFactory.getInstance().removeFlyweight(key);					}System.out.println("now thread="+fsMap.size()+",fsMap=="+fsMap.keySet());//休息1秒再重新判断try {Thread.sleep(1000L);} catch (InterruptedException e) {e.printStackTrace();}}}}
}