THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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| PlantUML |
|---|
@startuml
interface AutoCloseable {
void close()
}
interface ByteBufferSharing extends AutoCloseable {
ByteBuffer getBuffer()
ByteBuffer expandWriteBufferIfNeeded(int newCapacity)
ByteBuffer expandReadBufferIfNeeded(int newCapacity)
}
class ByteBufferVendor {
ByteBufferVendor(ByteBuffer bufferArg, BufferType bufferType, BufferPool bufferPool)
ByteBufferSharing open()
ByteBufferSharing open(long time, TimeUnit unit)
void destruct()
}
interface ByteBufferVendor.ByteBufferSharingInternal extends ByteBufferSharing {
void releaseBuffer()
}
class ByteBufferVendor.ByteBufferSharingInternalImpl implements ByteBufferVendor.ByteBufferSharingInternal {}
ByteBufferVendor "sharing" *-- ByteBufferVendor.ByteBufferSharingInternal
ByteBufferVendor "lock" *-- ReentrantLock
ByteBufferVendor "isDestructed" *-- AtomicBoolean
ByteBufferVendor "counter" *-- AtomicInteger
ByteBufferVendor.ByteBufferSharingInternalImpl "buffer\n0..1" --> "1" ByteBuffer
ByteBufferVendor.ByteBufferSharingInternalImpl "bufferPool\n*" --> "1" BufferPool
ByteBufferVendor.ByteBufferSharingInternalImpl "bufferType\n*" --> "1" BufferType
ByteBufferVendor .. ByteBuffer : derived\nassociation
@enduml |
ByteBuffers are not meant to be accessed concurrently. But our NioFilter classes, particularly, NioSslEngine manipulate ByteBuffers, and are themselves subject to concurrent access. As a result it's often necessary to protect ByteBuffers from concurrent access.
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In the class diagram at the top of this page you'll see a dotted association between ByteBufferVendor and ByteBuffer labeled "derived association". That's meant to convey the fact that kind of the whole point of the vendor is that it mediates access to a ByteBuffer. In UML terms, there is a derived association between the two, even though you won't see an explicit (direct) object reference in the code.
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| Code Block | ||||||
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ByteBufferSharing WRONG() throws IOException {
try (final ByteBufferSharing sharing = vendor.open()) {
// +1 net reference count
// access ByteBuffer through sharing reference here
// NEVER DO THIS: you risk the reference count dropping to zero
// before the caller can bind the reference value in its own
// try-with-resources block
return sharing
}
// +0 net reference count--buffer is potentially eligible
// for return to pool before caller can access it!
} |
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