一、介面繼承圖

二、介面類功能概述和實現

DataBuffer是對java NIO中的ByteBuffer 和Netty的ByteBuf 的統一包裝，包含對位元組緩衝區操作的各種方法，如下：

      DefaultDataBuffer是DataBuffer的預設實現，基於java NIO的ByteBuffer實現， 相關ByteBuffer的操作參考：

      PooledDataBuffer繼承DataBuffer介面，增加了引用計數的方法，保留方法將引用計數增加1。 釋放方法將計數減1，並在計數達到0時釋放緩衝區的記憶體，增加的方法如下：

    NettyDataBuffer是PooledDataBuffer的唯一實現，基於Netty 的ByteBuf實現。

    DataBufferFactory介面提供了用於構造DataBuffer的方法，如下所示：

其中join方法用於將多個DataBuffer做合併處理。DefaultDataBufferFactory是DefaultDataBuffer的工廠類，NettyDataBufferFactory是NettyDataBuffer的工廠類。

DataBufferUtils是DataBuffer介面的工具類，它包含從InputStream或NIO通道讀取DataBuffer物件的Flux的方法，以及將資料緩衝區Flux寫入OutputStream或Channel的方法等。但是該工具類是基於反應式程式設計框架Reactor中的Flux元素寫的，Reactor參考如下：https://www.ibm.com/developerworks/cn/java/j-cn-with-reactor-response-encode/index.html?lnk=hmhm

參考測試用例如下：

@Test
	public void writeAndRead() throws Exception{
		DataBufferFactory dataBufferFactory=new DefaultDataBufferFactory();
		DataBuffer buffer = dataBufferFactory.allocateBuffer(2);
		buffer.write(new byte[]{'a', 'b', 'c'});
		System.out.println("capacity-->"+buffer.capacity());
		System.out.println("readPosition-->"+buffer.readPosition());
		System.out.println("writePosition-->"+buffer.writePosition());
		System.out.println("writableByteCount-->"+buffer.writableByteCount());
		System.out.println("readableByteCount-->"+buffer.readableByteCount());

		int index=buffer.indexOf(p -> p=='c', 1);
		System.out.println("index-->"+index);

		int ch = buffer.read();
		assertEquals('a', ch);

		buffer.readPosition(2);
		ch = buffer.read();
		assertEquals('c', ch);

		buffer.write((byte) 'd');
		buffer.write((byte) 'e');

		byte[] result = new byte[2];
		buffer.read(result);

		assertArrayEquals(new byte[]{'d', 'e'}, result);

		ByteBuffer buffer2=ByteBuffer.allocate(4);
		buffer2.put((byte) '1');
		buffer2.put((byte) '2');
		buffer2.put((byte) '3');
		buffer2.put((byte) '4');
		buffer2.position(2);
		System.out.println("write before writePosition-->"+buffer.writePosition());
		buffer.write(buffer2);
		System.out.println("write after writePosition-->"+buffer.writePosition());

		ByteBuffer buffer3=buffer.asByteBuffer(4, 5);
		ch = buffer3.get();
		assertEquals('e', ch);
		assertEquals(5,buffer3.limit());

		InputStream in=buffer.asInputStream();
		in.read(result);
		assertArrayEquals(new byte[]{'3', '4'}, result);

		DataBufferUtils.release(buffer);
	}

	@Test
	public void retainAndRelease() {
		NettyDataBufferFactory dataBufferFactory=new NettyDataBufferFactory(new PooledByteBufAllocator());
		PooledDataBuffer buffer = dataBufferFactory.allocateBuffer(4);
//		buffer.write((byte) 'a');

		buffer.retain();
		boolean result = buffer.release();
		assertFalse(result);
		result = buffer.release();
		assertTrue(result);
	}
 

   三、ResourcePatternResolver和PropertySourceFactory介面