从Netty的ChannelBuffer.read找到了奇怪的索引自动发现错误?

在我的netty项目中有以下简单代码,它期望从上游读取一个整数。管道中没有编码器。

public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
        ChannelBuffer m = (ChannelBuffer) e.getMessage();

        m.readInt() 
    }

java.lang.IndexOutOfBoundsException
    at org.jboss.netty.buffer.AbstractChannelBuffer.checkReadableBytes(AbstractChannelBuffer.java:657)
    at org.jboss.netty.buffer.AbstractChannelBuffer.readInt(AbstractChannelBuffer.java:272)
    at PushServer.Netty.PushClientHandler.messageReceived(PushClientHandler.java:33)
    at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:274)
    at org.jboss.netty.channel.Channels.fireMessageReceived(Channels.java:261)
    at org.jboss.netty.channel.socket.nio.NioWorker.read(NioWorker.java:349)
    at org.jboss.netty.channel.socket.nio.NioWorker.processSelectedKeys(NioWorker.java:281)
    at org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:201)
    at org.jboss.netty.util.internal.IoWorkerRunnable.run(IoWorkerRunnable.java:46)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:637)

有什么想法吗?