Java设计模式（六）合成模式 享元模式

（十一）合成模式 Composite

合成模式是一组对象的组合，这些对象能够是容器对象，也能够是单对象。组对象同意包括单对象，也能够包括其它组对象，要为组合对象和单对象定义共同的行为。合成模式的意义是 保证client调用单对象与组合对象的一致性。

class TreeNode{
	private String name;
	private TreeNode parent;
	private Vector<TreeNode> children = new Vector<TreeNode>();
	public TreeNode(String name){
		this.name = name;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public TreeNode getParent() {
		return parent;
	}
	public void setParent(TreeNode parent) {
		this.parent = parent;
	}
	public void setChildren(Vector<TreeNode> children) {
		this.children = children;
	}
	//加入孩子节点
	public void add(TreeNode node){
		children.add(node);
	}
	//删除孩子节点
	public void remove(TreeNode node){
		children.remove(node);
	}
	//取得孩子节点
	public Enumeration<TreeNode> getChildren(){
		return children.elements();
	}
}
public class Composite {
	TreeNode root = null;
	public Composite(String name){
		root = new TreeNode(name);
	}
	public static void main(String[] args){
		Composite com = new Composite("A");
		TreeNode nodeb = new TreeNode("B");
		TreeNode nodec = new TreeNode("C");
		nodeb.add(nodec);
		com.root.add(nodeb);
	}
}

(十二) 享元模式 Flyweight

享元模式的主要目的是实现对象的共享，当系统中存在大量对象的时候降低内存开销。通常与工厂模式一同使用。

一个client请求时候。工厂检查当前对象池是否存在可用的对象，有就返回已经存在的对象。没有就创建一个新对象。数据库连接池就是最典型的运用享元模式的样例。

public class ConnectionPool implements IConnectionPool{
	private DBbean dbBean;	//连接池配置属性
	private boolean isActive = false;	//连接池活动状态
	private int contActive = 0;		//记录创建的总连接数
	private List<Connection> freeConnection = new Vector<Connection>();
	private List<Connection> activeConnection = new Vector<>();
	private static ThreadLocal<Connection> threadLocal = new ThreadLocal<>();
	public ConnectionPool(DBbean dbBean){
		super();
		this.dbBean = dbBean;
		init();
		cheackPool();
	}
	public void init(){
		try {
			Class.forName(dbBean.getDriverName());
			for(int i = 0;i < dbBean.getInitConnections();i++){
				Connection conn;
				conn = newConnection();
				if(conn != null){
					freeConnection.add(conn);
					contActive++;
				}
			}
			isActive = true;
		} catch (ClassNotFoundException | SQLException e) {
			e.printStackTrace();
		}
	}
	//获得当前连接数
	public Connection getCurrentConnection(){
		Connection conn = threadLocal.get();
		if(!isValid(conn)){
			conn = getConnection();
		}
		return conn;
	}
	// 获得连接
    public synchronized Connection getConnection() {
        Connection conn = null;
        try {
            // 推断是否超过最大连接数限制
            if(contActive < this.dbBean.getMaxActiveConnections()){
                if (freeConnection.size() > 0) {
                    conn = freeConnection.get(0);
                    if (conn != null) {
                        threadLocal.set(conn);
                    }
                    freeConnection.remove(0);
                } else {
                    conn = newConnection();
                }
            }else{
                // 继续获得连接,直到从新获得连接
                wait(this.dbBean.getConnTimeOut());
                conn = getConnection();
            }
            if (isValid(conn)) {
                activeConnection.add(conn);
                contActive ++;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return conn;
    }
    // 获得新连接
    private synchronized Connection newConnection()
            throws ClassNotFoundException, SQLException {
        Connection conn = null;
        if (dbBean != null) {
            Class.forName(dbBean.getDriverName());
            conn = DriverManager.getConnection(dbBean.getUrl(),
                    dbBean.getUserName(), dbBean.getPassword());
        }
        return conn;
    }
    // 释放连接
    public synchronized void releaseConn(Connection conn) throws SQLException {
        if (isValid(conn)&& !(freeConnection.size() > dbBean.getMaxConnections())) {
            freeConnection.add(conn);
            activeConnection.remove(conn);
            contActive --;
            threadLocal.remove();
            // 唤醒全部正待等待的线程，去抢连接
            notifyAll();
        }
    }
    // 推断连接是否可用
    private boolean isValid(Connection conn) {
    	try {
    		if (conn == null || conn.isClosed()) {
    			return false;
    		}
    	} catch (SQLException e) {
    		e.printStackTrace();
    	}
    	return true;
    }
    // 销毁连接池
    public synchronized void destroy() {
        for (Connection conn : freeConnection) {
            try {
                if (isValid(conn)) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        for (Connection conn : activeConnection) {
            try {
                if (isValid(conn)) {
                    conn.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        isActive = false;
        contActive = 0;
    }
    // 连接池状态
    @Override
    public boolean isActive() {
        return isActive;
    }
    // 定时检查连接池情况
    @Override
    public void cheackPool() {
        if(dbBean.isCheakPool()){
            new Timer().schedule(new TimerTask() {
            @Override
            public void run() {
            // 1.对线程里面的连接状态
            // 2.连接池最小 最大连接数
            // 3.其它状态进行检查。由于这里还须要写几个线程管理的类，临时就不加入了
            System.out.println("空线池连接数："+freeConnection.size());
            System.out.println("活动连接数：："+activeConnection.size());
            System.out.println("总的连接数："+contActive);
                }
            },dbBean.getLazyCheck(),dbBean.getPeriodCheck());
        }
    }
}