//init方法是线程池创建方法

public void init() throws SQLException {

...

this.createAndLogThread();

this.createAndStartCreatorThread();

//调用创建销毁线程方法

this.createAndStartDestroyThread();

this.initedLatch.await();

...

}

//创建销毁线程

protected void createAndStartDestroyThread() {

this.destroyTask = new DruidDataSource.DestroyTask();

if(this.destroyScheduler != null) {

long period = this.timeBetweenEvictionRunsMillis;

if(period <= 0L) {

period = 1000L;

}

//启动销毁线程

this.destroySchedulerFuture = this.destroyScheduler.scheduleAtFixedRate(this.destroyTask, period, period, TimeUnit.MILLISECONDS);

this.initedLatch.countDown();

} else {

String threadName = "Druid-ConnectionPool-Destroy-" + System.identityHashCode(this);

this.destroyConnectionThread = new DruidDataSource.DestroyConnectionThread(threadName);

this.destroyConnectionThread.start();

}

}

//销毁线程

public class DestroyTask implements Runnable {

public DestroyTask() {

}

public void run() {

//checkTime 为true

DruidDataSource.this.shrink(true, DruidDataSource.this.keepAlive);

if(DruidDataSource.this.isRemoveAbandoned()) {

DruidDataSource.this.removeAbandoned();

}

}

}

//具体方法

public void shrink(boolean checkTime, boolean keepAlive) {

try {

this.lock.lockInterruptibly();

} catch (InterruptedException var49) {

return;

}

boolean needFill = false;

int evictCount = 0;

int keepAliveCount = 0;

int fatalErrorIncrement = this.fatalErrorCount - this.fatalErrorCountLastShrink;

this.fatalErrorCountLastShrink = this.fatalErrorCount;

int checkCount;

label956: {

try {

if(this.inited) {

//可能被销毁数量 = 线程池当前线程数量 - 配置的最小空闲数

checkCount = this.poolingCount - this.minIdle;

long currentTimeMillis = System.currentTimeMillis();

int i;

for(i = 0; i < this.poolingCount; ++i) {

DruidConnectionHolder connection = this.connections[i];

if((this.onFatalError || fatalErrorIncrement > 0) && this.lastFatalErrorTimeMillis > connection.connectTimeMillis) {

this.keepAliveConnections[keepAliveCount++] = connection;

} else if(checkTime) {

long idleMillis;

if(this.phyTimeoutMillis > 0L) {

idleMillis = currentTimeMillis - connection.connectTimeMillis;

if(idleMillis > this.phyTimeoutMillis) {

this.evictConnections[evictCount++] = connection;

continue;

}

}

//当前for循环处理的线程空闲时间 = 当前时间 - 连接最后活跃时间

idleMillis = currentTimeMillis - connection.lastActiveTimeMillis;

if(idleMillis < this.minEvictableIdleTimeMillis && idleMillis < this.keepAliveBetweenTimeMillis) {

break;

}

//连接空闲时间 >= 配置的最小空闲被回收时间 : minEvictableIdleTimeMillis

if(idleMillis >= this.minEvictableIdleTimeMillis) {

/*

checkTime 为方法入参 = true,

i:当前for循环下标(连接取得时候是取得数组最大坐标,新创建的连接也是放在数组最大坐标上,所以0号坐标一定是最久未使用的那个)

可能被销毁数量 = 线程池当前线程数量 - 配置的最小空闲数(checkCount = this.poolingCount - this.minIdle; )

重点 : 也就是minEvictableIdleTimeMillis配置只会回收超过minIdle的那部分空闲连接

*/

if(checkTime && i < checkCount) {

this.evictConnections[evictCount++] = connection;

continue;

}

//连接空闲时间 > 配置的最大空闲时间maxEvictableIdleTimeMillis

//重点 : maxEvictableIdleTimeMillis参数会忽略配置的minIdle

if(idleMillis > this.maxEvictableIdleTimeMillis) {

this.evictConnections[evictCount++] = connection;

continue;

}

}

if(keepAlive && idleMillis >= this.keepAliveBetweenTimeMillis) {

this.keepAliveConnections[keepAliveCount++] = connection;

}

} else {

if(i >= checkCount) {

break;

}

this.evictConnections[evictCount++] = connection;

}

}

i = evictCount + keepAliveCount;

if(i > 0) { //复制有效连接到连接池数组

System.arraycopy(this.connections, i, this.connections, 0, this.poolingCount - i);

Arrays.fill(this.connections, this.poolingCount - i, this.poolingCount, (Object)null);

this.poolingCount -= i;

}

this.keepAliveCheckCount += keepAliveCount;

if(keepAlive && this.poolingCount + this.activeCount < this.minIdle) {

needFill = true;

}

break label956;

}

} finally {

this.lock.unlock();

}

return;

}

Connection connection;

DruidConnectionHolder holer;

if(evictCount > 0) { //销毁刚刚放在数组里的连接

for(checkCount = 0; checkCount < evictCount; ++checkCount) {

holer = this.evictConnections[checkCount];

connection = holer.getConnection();

JdbcUtils.close(connection);

destroyCountUpdater.incrementAndGet(this);

}

Arrays.fill(this.evictConnections, (Object)null);

}

...

}