private PooledConnection popConnection(String username, String password)
throws SQLException { // 获取一个连接
boolean countedWait = false;
PooledConnection conn = null;
long t = System.currentTimeMillis();
int localBadConnectionCount = 0;
while (conn == null) {
synchronized (state) {
if (!state.idleConnections.isEmpty()) { // pool里还有空闲连接
// Pool has available connection
conn = state.idleConnections.remove(0); // 从空闲list移出一个conn，用做新连接
if (log.isDebugEnabled()) {
log.debug("Checked out connection " + conn.getRealHashCode() + " from pool.");
}
} else { // pool里没有空闲连接了
// Pool does not have available connection
if (state.activeConnections.size() < poolMaximumActiveConnections) { // 活动list没有满
// Can create new connection
conn = new PooledConnection(dataSource.getConnection(), this); // 新建一个PooledConnection
if (log.isDebugEnabled()) {
log.debug("Created connection " + conn.getRealHashCode() + ".");
}
} else { // 活动list已经满了，无法创建新连接
// Cannot create new connection
PooledConnection oldestActiveConnection = state.activeConnections.get(0); // 获取最早开始活动的连接
long longestCheckoutTime =
oldestActiveConnection.getCheckoutTime(); // 获得最老的活动连接的checkout时间
if (longestCheckoutTime > poolMaximumCheckoutTime) { // 如果checkout时间大于最大值
// Can claim overdue connection
state.claimedOverdueConnectionCount++; // 过期连接计数++
state.accumulatedCheckoutTimeOfOverdueConnections +=
longestCheckoutTime; // 累加过期连接的checkout时间
state.accumulatedCheckoutTime += longestCheckoutTime; // 累加checkout时间
state.activeConnections.remove(oldestActiveConnection); // 从活动list移出最老的活动连接，留出空位来啦
if (!oldestActiveConnection.getRealConnection().getAutoCommit()) {
oldestActiveConnection.getRealConnection().rollback(); // 回滚
}
conn =
new PooledConnection(
oldestActiveConnection.getRealConnection(), this); // 新建连接，用最老连接的真连接
oldestActiveConnection.invalidate(); // 最老连接标记无效
if (log.isDebugEnabled()) {
log.debug("Claimed overdue connection " + conn.getRealHashCode() + ".");
}
} else { // 如果checkout时间并没有超过最大值，必须等待
// Must wait
try {
if (!countedWait) { // countedWait原来是false
state.hadToWaitCount++; // 必须等待的计数++
countedWait = true; // countedWait变为true
}
if (log.isDebugEnabled()) {
log.debug(
"Waiting as long as " + poolTimeToWait + " milliseconds for connection.");
}
long wt = System.currentTimeMillis();
state.wait(
poolTimeToWait); // 等poolTimeToWait微秒，pushConnection移出一个连接时会notifyAll来唤醒wait的线程
state.accumulatedWaitTime += System.currentTimeMillis() - wt;
} catch (InterruptedException e) {
break;
}
}
}
}
if (conn != null) { // conn非空，确实建出来了
if (conn.isValid()) { // conn有效
if (!conn.getRealConnection().getAutoCommit()) {
conn.getRealConnection().rollback(); // 这里回滚是干啥？ hama
}
conn.setConnectionTypeCode(
assembleConnectionTypeCode(dataSource.getUrl(), username, password));
conn.setCheckoutTimestamp(System.currentTimeMillis());
conn.setLastUsedTimestamp(System.currentTimeMillis());
state.activeConnections.add(conn); // 加入活动list
state.requestCount++;
state.accumulatedRequestTime += System.currentTimeMillis() - t;
} else { // conn无效
if (log.isDebugEnabled()) {
log.debug(
"A bad connection ("
+ conn.getRealHashCode()
+ ") was returned from the pool, getting another connection.");
}
state.badConnectionCount++;
localBadConnectionCount++;
conn = null;
if (localBadConnectionCount > (poolMaximumIdleConnections + 3)) {
if (log.isDebugEnabled()) {
log.debug("PooledDataSource: Could not get a good connection to the database.");
}
throw new SQLException(
"PooledDataSource: Could not get a good connection to the database.");
}
}
}
}
} // 到这里while结束
if (conn == null) { // 出现了奇葩的Unknown错吧
if (log.isDebugEnabled()) {
log.debug(
"PooledDataSource: Unknown severe error condition. The connection pool returned a null connection.");
}
throw new SQLException(
"PooledDataSource: Unknown severe error condition. The connection pool returned a null connection.");
}
return conn;
}
private PooledConnection popConnection(String username, String password) throws SQLException {
boolean countedWait = false;
PooledConnection conn = null;
long t = System.currentTimeMillis();
int localBadConnectionCount = 0;
while (conn == null) {
synchronized (state) {
if (state.idleConnections.size() > 0) {
// Pool has available connection
conn = (PooledConnection) state.idleConnections.remove(0);
if (log.isDebugEnabled()) {
log.debug("Checked out connection " + conn.getRealHashCode() + " from pool.");
}
} else {
// Pool does not have available connection
if (state.activeConnections.size() < poolMaximumActiveConnections) {
// Can create new connection
conn = new PooledConnection(dataSource.getConnection(), this);
@SuppressWarnings("unused")
// used in logging, if enabled
Connection realConn = conn.getRealConnection();
if (log.isDebugEnabled()) {
log.debug("Created connection " + conn.getRealHashCode() + ".");
}
} else {
// Cannot create new connection
PooledConnection oldestActiveConnection =
(PooledConnection) state.activeConnections.get(0);
long longestCheckoutTime = oldestActiveConnection.getCheckoutTime();
if (longestCheckoutTime > poolMaximumCheckoutTime) {
// Can claim overdue connection
state.claimedOverdueConnectionCount++;
state.accumulatedCheckoutTimeOfOverdueConnections += longestCheckoutTime;
state.accumulatedCheckoutTime += longestCheckoutTime;
state.activeConnections.remove(oldestActiveConnection);
if (!oldestActiveConnection.getRealConnection().getAutoCommit()) {
oldestActiveConnection.getRealConnection().rollback();
}
conn = new PooledConnection(oldestActiveConnection.getRealConnection(), this);
oldestActiveConnection.invalidate();
if (log.isDebugEnabled()) {
log.debug("Claimed overdue connection " + conn.getRealHashCode() + ".");
}
} else {
// Must wait
try {
if (!countedWait) {
state.hadToWaitCount++;
countedWait = true;
}
if (log.isDebugEnabled()) {
log.debug(
"Waiting as long as " + poolTimeToWait + " milliseconds for connection.");
}
long wt = System.currentTimeMillis();
state.wait(poolTimeToWait);
state.accumulatedWaitTime += System.currentTimeMillis() - wt;
} catch (InterruptedException e) {
break;
}
}
}
}
if (conn != null) {
if (conn.isValid()) {
if (!conn.getRealConnection().getAutoCommit()) {
conn.getRealConnection().rollback();
}
conn.setConnectionTypeCode(
assembleConnectionTypeCode(dataSource.getUrl(), username, password));
conn.setCheckoutTimestamp(System.currentTimeMillis());
conn.setLastUsedTimestamp(System.currentTimeMillis());
state.activeConnections.add(conn);
state.requestCount++;
state.accumulatedRequestTime += System.currentTimeMillis() - t;
} else {
if (log.isDebugEnabled()) {
log.debug(
"A bad connection ("
+ conn.getRealHashCode()
+ ") was returned from the pool, getting another connection.");
}
state.badConnectionCount++;
localBadConnectionCount++;
conn = null;
if (localBadConnectionCount > (poolMaximumIdleConnections + 3)) {
if (log.isDebugEnabled()) {
log.debug("PooledDataSource: Could not get a good connection to the database.");
}
throw new SQLException(
"PooledDataSource: Could not get a good connection to the database.");
}
}
}
}
}
if (conn == null) {
if (log.isDebugEnabled()) {
log.debug(
"PooledDataSource: Unknown severe error condition. The connection pool returned a null connection.");
}
throw new SQLException(
"PooledDataSource: Unknown severe error condition. The connection pool returned a null connection.");
}
return conn;
}