等待超时模式在数据库连接池中的使用

在常用的数据库连接池中就应用了等待超时模式，在代码示例中模拟从连接池中获取连接，使用和释放连接的过程。而客户端获取连接的过程被设定为等待超时的模式，

也就是在超时时间内如果无法获取到可用连接，将会返回一个null、设定连接池的数量为10个，然后通过条件客户端的线程数来模拟无法获取连接的场景。

public class ConnectionPool {
    private LinkedList<Connection> pool = new LinkedList<Connection>();
    private int initialSize = 10;

    /**
     * 初始化连接池
     * @param initialSize
     */
    public ConnectionPool(int initialSize) {
        if(initialSize > 0) {
            this.initialSize = initialSize;
        }
        for(int i=0;i<initialSize;i++){
            pool.addLast(ConnectionDriver.createConnection());
        }
    }

    /**
     * 释放连接池中的连接
     * @param connection
     */
    public void releaseConnection(Connection connection){
        if(connection != null){
            synchronized (pool){
                //连接放回连接池
                pool.addLast(connection);
                //连接放回连接池后，需要通知其他线程连接池中已经归还了一个连接，可以获取连接了
                pool.notifyAll();
            }
        }
    }
    public Connection borrowConnection(long mills) throws InterruptedException{
        synchronized (pool){
            if(mills <= 0){
                while (pool.isEmpty()){
                    pool.wait();
                }
                return pool.removeFirst();
            }else{
                long future = System.currentTimeMillis() + mills;
                long remaining = mills;
                while (pool.isEmpty() && remaining > 0){
                    pool.wait(remaining);
                    remaining = future - System.currentTimeMillis();
                }
                Connection result = null;
                if(!pool.isEmpty()){
                    result = pool.removeFirst();
                }
                return result;
            }
        }
    }
}

public class ConnectionDriver {
    /**
     * 创建一个Connection的代理，在commit时休眠100毫秒
     * @return
     */
    public static final Connection createConnection() {
        return (Connection) Proxy.newProxyInstance(ConnectionDriver.class.getClassLoader(), new Class<?>[]{Connection.class}, new ConnectionHndler());
    }

    static class ConnectionHndler implements InvocationHandler {
        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            if (method.getName().equals("commit")) {
                TimeUnit.MICROSECONDS.sleep(100);
            }
            return null;
        }
    }

}

public class ConnectionPoolTest {
    static ConnectionPool pool = new ConnectionPool(10);
    //保证所有的ConnectionThread线程能够同时开始
    static CountDownLatch start = new CountDownLatch(1);
    static CountDownLatch end;

    public static void main(String[] args) throws Exception{
        int threadCount = 1000;
        end = new CountDownLatch(threadCount);
        int count = 20;
        AtomicInteger got = new AtomicInteger();
        AtomicInteger notGot = new AtomicInteger();
        for(int i=0;i<threadCount;i++){
            Thread thread = new Thread(new ConnectionThread(count,got,notGot),"ConnectionThread");
            thread.start();
        }
        start.countDown();
        end.await();
        System.out.println("total invoke:"+(threadCount*count));
        System.out.println("got coonection:"+got);
        System.out.println("not got connection:"+notGot);
    }


    static class ConnectionThread implements Runnable{
        int count;
        AtomicInteger got;
        AtomicInteger notGot;

        public ConnectionThread(int count, AtomicInteger got, AtomicInteger notGot) {
            this.count = count;
            this.got = got;
            this.notGot = notGot;
        }

        @Override
        public void run() {
            try {
                start.await();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            while (count > 0){
                try {
                    Connection connection = pool.borrowConnection(1000);
                    if(connection != null){
                        try {
                            connection.createStatement();
                            connection.commit();
                        }finally {
                            pool.releaseConnection(connection);
                            got.incrementAndGet();
                        }
                    }else{
                        notGot.incrementAndGet();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }finally {
                    count--;
                }
            }
            end.countDown();
        }
    }
}

来源：CSDN

作者：one-fly

链接：https://blog.csdn.net/f529352479/article/details/51786281