為什么即使 MethodHandle 沒問題，在 invokeExact 上也會得到 WrongMethodTypeException

Question

我正在嘗試調用一個 invoke 方法，但有一個我無法解釋的錯誤。 我聽說 Invoke Exact 方法必須返回，但即使那時它也不起作用。

public boolean exec(String id, ChannelHandlerContext ctx, ByteBuf byteBuf) {
        assert ctx != null;
        assert byteBuf != null;

        MethodHandle methodHandle = this.idMethods.get(id);
        if(methodHandle != null) {
            try {
                Object object = this.idObjects.get(id);

                Boolean b = (Boolean) methodHandle.invokeExact(object, ctx, byteBuf);

                return true;
            } catch (Throwable throwable) {
                throwable.printStackTrace();
            }
        }
        return false;
}

在此代碼上程序崩潰

Boolean b = (Boolean) methodHandle.invokeExact(object, ctx, byteBuf);

java.lang.invoke.WrongMethodTypeException: expected (,ChannelHandlerContext,ByteBuf)boolean but found (Object,ChannelHandlerContext,ByteBuf)Boolean
at java.lang.invoke.Invokers.newWrongMethodTypeException(Invokers.java:298)
at java.lang.invoke.Invokers.checkExactType(Invokers.java:309)
at de.moldiy.molnet.MessageExchangerManager.exec(MessageExchangerManager.java:54)
at de.moldiy.molnet.MessageHandler.channelRead0(MessageHandler.java:22)
at de.moldiy.molnet.MessageHandler.channelRead0(MessageHandler.java:7)
at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:99)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:324)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:296)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357)
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:714)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:650)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:576)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:493)
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989)
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.lang.Thread.run(Thread.java:836)

這是包含我要調用的方法的類

s.loadMessageExchanger(new ServerMessageExchanger() {
    @TrafficID(id = "cords")
    public Boolean setCords(ChannelHandlerContext ctx,ByteBuf byteBuf) {
       System.out.println("jaaa");
       return true;
    }
});

Answer 1

由於您正在調用ServerMessageExchanger實例上的ServerMessageExchanger ，因此需要將該實例作為第一個參數傳遞給MethodHandle.invokeExact 。

像這樣的東西：

ServerMessageExchanger sme;
....
MethodHandle methodHandle = this.methods.get(id);
Boolean b = (Boolean) methodHandle.invokeExact(sme, ctx, byteBuf);

Answer 2

我現在知道出了什么問題，使用 invokeExact 您不能定義匿名類，因為必須從一開始就知道類型，所以這是不可能的：

        Object object = this.idObjects.get(id);

        methodHandle.invokeExact(object, ctx, byteBuf);

但我只能使用調用：

        Object object = this.idObjects.get(id);

        methodHandle.invoke(object, ctx, byteBuf);