Add reference counting for UndertowDataBuffer

This commit adds proper reference counting to the UndertowDataBuffer.

Author: poutsma

spring-web/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpRequest.java

@@ -24,6 +24,7 @@
 import java.net.URISyntaxException;
 import java.nio.ByteBuffer;
 import java.nio.charset.Charset;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.IntPredicate;
 import javax.net.ssl.SSLSession;
 
@@ -211,31 +212,45 @@ private static class UndertowDataBuffer implements PooledDataBuffer {
 
 		private final PooledByteBuffer pooledByteBuffer;
 
+		private final AtomicInteger refCount;
+
 		public UndertowDataBuffer(DataBuffer dataBuffer, PooledByteBuffer pooledByteBuffer) {
 			this.dataBuffer = dataBuffer;
 			this.pooledByteBuffer = pooledByteBuffer;
+			this.refCount = new AtomicInteger(1);
+		}
+
+		private UndertowDataBuffer(DataBuffer dataBuffer, PooledByteBuffer pooledByteBuffer,
+				AtomicInteger refCount) {
+			this.refCount = refCount;
+			this.dataBuffer = dataBuffer;
+			this.pooledByteBuffer = pooledByteBuffer;
 		}
 
 		@Override
 		public boolean isAllocated() {
-			return this.pooledByteBuffer.isOpen();
+			return this.refCount.get() > 0;
 		}
 
 		@Override
 		public PooledDataBuffer retain() {
+			this.refCount.incrementAndGet();
+			DataBufferUtils.retain(this.dataBuffer);
 			return this;
 		}
 
 		@Override
 		public boolean release() {
-			boolean result;
-			try {
-				result = DataBufferUtils.release(this.dataBuffer);
-			}
-			finally {
-				this.pooledByteBuffer.close();
+			int refCount = this.refCount.decrementAndGet();
+			if (refCount == 0) {
+				try {
+					return DataBufferUtils.release(this.dataBuffer);
+				}
+				finally {
+					this.pooledByteBuffer.close();
+				}
 			}
-			return result && this.pooledByteBuffer.isOpen();
+			return false;
 		}
 
 		@Override
@@ -280,7 +295,8 @@ public int writePosition() {
 
 		@Override
 		public DataBuffer writePosition(int writePosition) {
-			return this.dataBuffer.writePosition(writePosition);
+			this.dataBuffer.writePosition(writePosition);
+			return this;
 		}
 
 		@Override
@@ -290,12 +306,14 @@ public int capacity() {
 
 		@Override
 		public DataBuffer capacity(int newCapacity) {
-			return this.dataBuffer.capacity(newCapacity);
+			this.dataBuffer.capacity(newCapacity);
+			return this;
 		}
 
 		@Override
 		public DataBuffer ensureCapacity(int capacity) {
-			return this.dataBuffer.ensureCapacity(capacity);
+			this.dataBuffer.ensureCapacity(capacity);
+			return this;
 		}
 
 		@Override
@@ -310,47 +328,56 @@ public byte read() {
 
 		@Override
 		public DataBuffer read(byte[] destination) {
-			return this.dataBuffer.read(destination);
+			this.dataBuffer.read(destination);
+			return this;
 		}
 
 		@Override
 		public DataBuffer read(byte[] destination, int offset, int length) {
-			return this.dataBuffer.read(destination, offset, length);
+			this.dataBuffer.read(destination, offset, length);
+			return this;
 		}
 
 		@Override
 		public DataBuffer write(byte b) {
-			return this.dataBuffer.write(b);
+			this.dataBuffer.write(b);
+			return this;
 		}
 
 		@Override
 		public DataBuffer write(byte[] source) {
-			return this.dataBuffer.write(source);
+			this.dataBuffer.write(source);
+			return this;
 		}
 
 		@Override
 		public DataBuffer write(byte[] source, int offset, int length) {
-			return this.dataBuffer.write(source, offset, length);
+			this.dataBuffer.write(source, offset, length);
+			return this;
 		}
 
 		@Override
 		public DataBuffer write(DataBuffer... buffers) {
-			return this.dataBuffer.write(buffers);
+			this.dataBuffer.write(buffers);
+			return this;
 		}
 
 		@Override
 		public DataBuffer write(ByteBuffer... byteBuffers) {
-			return this.dataBuffer.write(byteBuffers);
+			this.dataBuffer.write(byteBuffers);
+			return this;
 		}
 
 		@Override
 		public DataBuffer write(CharSequence charSequence, Charset charset) {
-			return this.dataBuffer.write(charSequence, charset);
+			this.dataBuffer.write(charSequence, charset);
+			return this;
 		}
 
 		@Override
 		public DataBuffer slice(int index, int length) {
-			return this.dataBuffer.slice(index, length);
+			DataBuffer slice = this.dataBuffer.slice(index, length);
+			return new UndertowDataBuffer(slice, this.pooledByteBuffer, this.refCount);
 		}
 
 		@Override