public T borrowObject(long borrowMaxWaitMillis) throws Exception {
assertOpen();
//是否在获取对象的时候检查对象，开启的话则检查【主要是检查过期】
AbandonedConfig ac = this.abandonedConfig;
if (ac != null && ac.getRemoveAbandonedOnBorrow() &&
(getNumIdle() < 2) &&
(getNumActive() > getMaxTotal() - 3) ) {
removeAbandoned(ac);
}
PooledObject<T> p = null;
// Get local copy of current config so it is consistent for entire
// method execution
//当池耗尽的时候是否block，如果block的话则会idleObjects.pollFirst(borrowMaxWaitMillis,TimeUnit.MILLISECONDS);否则直接throw new NoSuchElementException("Pool exhausted");
boolean blockWhenExhausted = getBlockWhenExhausted();
boolean create;
long waitTime = 0;
while (p == null) {
create = false;
if (blockWhenExhausted) {
p = idleObjects.pollFirst();
if (p == null) {
create = true;
p = create();
}
if (p == null) {
if (borrowMaxWaitMillis < 0) {
p = idleObjects.takeFirst();
} else {
waitTime = System.currentTimeMillis();
p = idleObjects.pollFirst(borrowMaxWaitMillis,
TimeUnit.MILLISECONDS);
waitTime = System.currentTimeMillis() - waitTime;
}
}
if (p == null) {
throw new NoSuchElementException(
"Timeout waiting for idle object");
}
if (!p.allocate()) {
p = null;
}
} else {
p = idleObjects.pollFirst();
if (p == null) {
create = true;
p = create();
}
if (p == null) {
throw new NoSuchElementException("Pool exhausted");
}
if (!p.allocate()) {
p = null;
}
}
if (p != null) {
try {
//激活对象
factory.activateObject(p);
} catch (Exception e) {
try {
destroy(p);
} catch (Exception e1) {
// Ignore - activation failure is more important
}
p = null;
if (create) {
NoSuchElementException nsee = new NoSuchElementException(
"Unable to activate object");
nsee.initCause(e);
throw nsee;
}
}
//如果获取对象是检查则validateObject
if (p != null && getTestOnBorrow()) {
boolean validate = false;
Throwable validationThrowable = null;
try {
validate = factory.validateObject(p);
} catch (Throwable t) {
PoolUtils.checkRethrow(t);
validationThrowable = t;
}
//检查不通过则destroy
if (!validate) {
try {
destroy(p);
destroyedByBorrowValidationCount.incrementAndGet();
} catch (Exception e) {
// Ignore - validation failure is more important
}
p = null;
if (create) {
NoSuchElementException nsee = new NoSuchElementException(
"Unable to validate object");
nsee.initCause(validationThrowable);
throw nsee;
}
}
}
}
}
updateStatsBorrow(p, waitTime);
return p.getObject();
}
