1.buffer包结构：
2.核心类：IoBuffer
A byte buffer used by MINA applications.
This is a replacement for ByteBuffer. Please refer to ByteBuffer documentation for preliminary usage. MINA does not use NIO ByteBuffer directly for two reasons:
It doesn't provide useful getters and putters such as fill, get/putString, and get/putAsciiInt() enough.
It is difficult to write variable-length data due to its fixed capacity
(1)IoBuffer基于以下两个原因，取代Nio标准包中的ByteBuffer，在mina中缓存字节
（a）提供 get/putString、get/putAsciiInt()等方法来填充数据
（b）可供扩展长度数据使用
(2)基本操作
Allocation：IoBuffer buf = IoBuffer.allocate(1024, false); //false,true代表是否useDirectBuffer
AutoExpand： buf.setAutoExpand(true);
AutoShrink：自动设置buf.setAutoShrink(true)，手工设置shrink（）
(3)抽象类AbstractIoBuffer及代理方法IoBufferWrapper继承于IoBuffer
(4)IoBuffer分配方式：IoBufferAllocator
默认为：private static IoBufferAllocator allocator = new SimpleBufferAllocator();
可通过 ：public static void setAllocator(IoBufferAllocator newAllocator)来改变这个分配方式
其中有继承于IoBufferAllocator的类有：SimpleBufferAllocator、CachedBufferAllocator