详解Mybatis中的PooledDataSource

   class PooledConnection implements InvocationHandler {
    private static final Class<?>[] IFACES = new Class<?>[] { Connection.class };
    public PooledConnection(Connection connection, PooledDataSource dataSource) {
        this.hashCode = connection.hashCode();
        this.realConnection = connection;
        this.dataSource = dataSource;
        this.createdTimestamp = System.currentTimeMillis();
        this.lastUsedTimestamp = System.currentTimeMillis();
        this.valid = true;
        this.proxyConnection = (Connection) Proxy.newProxyInstance(Connection.class.getClassLoader(), IFACES, this);
    }
    
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        String methodName = method.getName();
        if (CLOSE.equals(methodName)) {
            dataSource.pushConnection(this);
            return null;
        }
        try {
            if (!Object.class.equals(method.getDeclaringClass())) {
                checkConnection();
            }
            return method.invoke(realConnection, args);
        } catch (Throwable t) {
            throw ExceptionUtil.unwrapThrowable(t);
        }
    }
}

protected void pushConnection(PooledConnection conn) throws SQLException {
        synchronized (state) {
            state.activeConnections.remove(conn);
            if (conn.isValid()) {
                if (state.idleConnections.size() < poolMaximumIdleConnections && conn.getConnectionTypeCode() == expectedConnectionTypeCode) {
                    state.accumulatedCheckoutTime += conn.getCheckoutTime();
                    if (!conn.getRealConnection().getAutoCommit()) {
                        conn.getRealConnection().rollback();
                    }
                    PooledConnection newConn = new PooledConnection(conn.getRealConnection(), this);
                    state.idleConnections.add(newConn);
                    newConn.setCreatedTimestamp(conn.getCreatedTimestamp());
                    newConn.setLastUsedTimestamp(conn.getLastUsedTimestamp());
                    conn.invalidate(); 
                    if (log.isDebugEnabled()) {
                        log.debug("Returned connection " + newConn.getRealHashCode() + " to pool.");
                    }
                    state.notifyAll();
                } else {

                    state.accumulatedCheckoutTime += conn.getCheckoutTime();
                    if (!conn.getRealConnection().getAutoCommit()) {
                        conn.getRealConnection().rollback();
                    }
                    conn.getRealConnection().close();
                    if (log.isDebugEnabled()) {
                        log.debug("Closed connection " + conn.getRealHashCode() + ".");
                    }
                    conn.invalidate();
                }
            } else {
                if (log.isDebugEnabled()) {
                    log.debug("A bad connection (" + conn.getRealHashCode() + ") attempted to return to the pool, discarding connection.");
                }
                state.badConnectionCount++;
            }
        }
    }