java Netty如何发送对象

Question

如何使用netty发送对象。当我尝试发送字符串对象时，一切都正常

channel.writeAndFlush(new String("df"));

但当我试图发送一个简单的对象服务器时，会出现错误

public class Message implements Serializable {

    private static final long serialVersionUID = 1L;
}
channel.writeAndFlush(new Message()); 

---

io.netty.channel.DefaultChannelPipeline$TailHandler exceptionCaught
WARNING: An exceptionCaught() event was fired, and it reached at the tail of the pipeline. It usually means the last handler in the pipeline did not handle the exception.
io.netty.handler.codec.DecoderException: java.lang.NullPointerException
    at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:259)
    at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:141)
    at io.netty.channel.DefaultChannelHandlerContext.invokeChannelRead(DefaultChannelHandlerContext.java:340)
    at io.netty.channel.DefaultChannelHandlerContext.fireChannelRead(DefaultChannelHandlerContext.java:326)
    at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:785)
    at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:116)
    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:494)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:461)
    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:378)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:350)
    at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:101)
    at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.NullPointerException
    at io.netty.handler.codec.serialization.CompactObjectInputStream.readClassDescriptor(CompactObjectInputStream.java:55)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1601)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1517)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1771)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1350)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:370)
    at io.netty.handler.codec.serialization.ObjectDecoder.decode(ObjectDecoder.java:73)
    at io.netty.handler.codec.LengthFieldBasedFrameDecoder.decode(LengthFieldBasedFrameDecoder.java:343)
    at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:228)
    ... 11 more

---

class ChatServerInitializer extends ChannelInitializer<SocketChannel> {

    @Override
    protected void initChannel(SocketChannel arg0) throws Exception
    {
        ChannelPipeline pipeline = arg0.pipeline();
        pipeline.addLast("decoder", (new ObjectDecoder(null)));  
        pipeline.addLast("encoder", new ObjectEncoder());  
        pipeline.addLast("handler", new ChatServerHandler());
    }
}

Answer 1

在构造ObjectDecoder时指定了null，这导致了这里的NullPointerException。相反，您必须指定类似ClassResolvers.weakCachingResolver(MyMessage.class.getClassLoader())的内容