ObjectPool抽象化父類別
複製代碼代碼如下:
import java.util.Iterator;
import java.util.Vector;
public abstract class ObjectPool<T> {
private Vector<T> locked, unlocked; // locked是已佔用的物件集合，unlocked是可用物件集合
public ObjectPool() {
locked = new Vector<T>();
unlocked = new Vector<T>();
}
// 建立物件
protected abstract T create();
// 驗證物件有效性
public abstract boolean validate(T o);
// 使物件失效
public abstract void expire(T o);
// 檢出：從物件池取得對象
public synchronized T checkOut() {
T t;
if (unlocked.size() > 0) {
Iterator<T> iter = unlocked.iterator();
while(iter.hasNext()) {
t = iter.next();
if(validate(t)) { // 物件有效
unlocked.remove(t);
locked.add(t);
return t;
}
else { // 物件已經失效
unlocked.remove(t);
expire(t);
}
}
}
// 物件池塘沒有可用對象，建立新對象
t = create();
locked.add(t);
return (t);
}
// 檢入：釋放物件回物件池
public synchronized void checkIn(T t) {
locked.remove(t);
if(validate(t)) { // 若物件仍有效則放回可用物件集合中
unlocked.add(t);
}
else { // 否則使物件失效
expire(t);
}
}
}
JDBCConnectionPool子類
複製代碼代碼如下:
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class JDBCConnectionPool extends ObjectPool<Connection> {
private String url, usr, pwd;
public JDBCConnectionPool(String driver, String url, String usr, String pwd) {
super();
// 載入對應的資料庫驅動
try {
Class.forName(driver).newInstance();
}
catch(Exception e) {
e.printStackTrace();
}
this.url = url;
this.usr = usr;
this.pwd = pwd;
}
@Override
protected Connection create() {
try {
return DriverManager.getConnection(url, usr, pwd);
}
catch(SQLException e) {
e.printStackTrace();
}
return null;
}
@Override
public boolean validate(Connection o) {
try {
return o.isClosed();
}
catch(SQLException e) {
e.printStackTrace();
}
return false;
}
@Override
public void expire(Connection o) {
try {
o.close();
}
catch(SQLException e) {
e.printStackTrace();
}
finally {
o = null;
}
}
public static void main(String[] args) {
JDBCConnectionPool dbConnPool = new JDBCConnectionPool("com.mysql.jdbc.Driver", "jdbc:mysql://127.0.0.1:3306/test", "root", "123");
// 取得資料庫連線對象
Connection conn = dbConnPool.checkOut();
// 使用資料庫連接對象
// ...
// 釋放資料庫連線對象
dbConnPool.checkIn(conn);
}
}
複製代碼代碼如下:
class Pool {
private static final MAX_AVAILABLE = 100;
private final Semaphore available = new Semaphore(MAX_AVAILABLE, true);
public Object getItem() throws InterruptedException {
available.acquire();
return getNextAvailableItem();
}
public void putItem(Object x) {
if (markAsUnused(x))
available.release();
}
// Not a particularly efficient data structure; just for demo
protected Object[] items = ... whatever kinds of items being managed
protected boolean[] used = new boolean[MAX_AVAILABLE];
protected synchronized Object getNextAvailableItem() {
for (int i = 0; i < MAX_AVAILABLE; ++i) {
if (!used[i]) {
used[i] = true;
return items[i];
}
}
return null; // not reached
}
protected synchronized boolean markAsUnused(Object item) {
for (int i = 0; i < MAX_AVAILABLE; ++i) {
if (item == items[i]) {
if (used[i]) {
used[i] = false;
return true;
} else
return false;
}
}
return false;
}
}