Netty内存泄漏解决ERROR io.netty.util.ResourceLeakDetector - LEAK: ByteBuf.release() was not called before it's garbage-collected

最近用Netty框架开发网络应用时，出现几个异常报错，仔细一看是内存泄漏了，提示ByteBuf对象在回收之前没有调用ByteBuf.release()

ERROR io.netty.util.ResourceLeakDetector - LEAK: ByteBuf.release() was not called before it's garbage-collected

出现这个问题是因为程序中生成了池化的ByteBuf（PooledByteBuf)。PooledByteBuf的内存空间是从内存池中分配的，并且内部维持了一个计数器，用来记录引用次数。PooledByteBuf在使用完之后要手动调用release()函数，该函数会减小引用次数，减小到0时就会将内存归还在内存池中。如果不调用release()函数，JVM不知道引用计数的存在，释放该对象时，可能还有其他引用在使用该内存空间，该内存空间也无法归还到内存池中，从而导致内存泄漏。

关于ByteBuf内存泄漏更详细的资料请移步Netty中ByteBuf内存泄露及释放解析 

解决方法就是找到报错的位置，找到生成的ByteBuf对象，在使用完之后调用对象的relesse()函数或者加上一句ReferenceCountUtil.release(msg)。如下面我出现的报错

2020-06-12 17:04:41.242 [nioEventLoopGroup-2-1] ERROR io.netty.util.ResourceLeakDetector - LEAK: ByteBuf.release() was not called before it's garbage-collected. See https://netty.io/wiki/reference-counted-objects.html for more information.
Recent access records: 
Created at:
    io.netty.buffer.PooledByteBufAllocator.newDirectBuffer(PooledByteBufAllocator.java:363)
    io.netty.buffer.AbstractByteBufAllocator.directBuffer(AbstractByteBufAllocator.java:187)
    io.netty.buffer.AbstractByteBufAllocator.buffer(AbstractByteBufAllocator.java:123)
    io.netty.buffer.AbstractByteBuf.readBytes(AbstractByteBuf.java:872)
    com.spring.netty.twg.service.TwgMessageDecoder.formatDecoder(TwgMessageDecoder.java:176)
    com.spring.netty.twg.service.TwgMessageDecoder.getMessageBody(TwgMessageDecoder.java:90)
    com.spring.netty.twg.service.TwgMessageDecoder.decode(TwgMessageDecoder.java:76)
    io.netty.handler.codec.LengthFieldBasedFrameDecoder.decode(LengthFieldBasedFrameDecoder.java:332)
    io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:501)

在formatDecoder函数中，我调用readBytes()函数生成新ByteBuf对象byteBufChar。

在使用结束时，调用byteBufChar的release()函数  byteBufChar.release();

2020-06-12 17:04:45.460 [nioEventLoopGroup-2-1] ERROR io.netty.util.ResourceLeakDetector - LEAK: ByteBuf.release() was not called before it's garbage-collected. See https://netty.io/wiki/reference-counted-objects.html for more information.
Recent access records: 
Created at:
    io.netty.buffer.SimpleLeakAwareByteBuf.unwrappedDerived(SimpleLeakAwareByteBuf.java:143)
    io.netty.buffer.SimpleLeakAwareByteBuf.retainedSlice(SimpleLeakAwareByteBuf.java:57)
    io.netty.handler.codec.LengthFieldBasedFrameDecoder.extractFrame(LengthFieldBasedFrameDecoder.java:498)
    io.netty.handler.codec.LengthFieldBasedFrameDecoder.decode(LengthFieldBasedFrameDecoder.java:437)
    com.spring.netty.twg.service.TwgMessageDecoder.decode(TwgMessageDecoder.java:31)
    io.netty.handler.codec.LengthFieldBasedFrameDecoder.decode(LengthFieldBasedFrameDecoder.java:332)

在decode函数中，我调用了父类的decode()函数，生成新BytyBuf对象in，

在使用结束时，调用工具类，帮助回收in对象  ReferenceCountUtil.release(in)或者直接调用release()