java - 为什么我的 BufferedInputStream.read() 不能接收 -1？

Question

伙计们，我一直在尝试编写一个使用 TCP 传输 JSON 字符串的程序。问题是，当我调用 BufferedInputStream.read() 时，我无法收到任何 -1 来指示 JSON 字符串的结尾。

我的服务器代码是:

public void listen() {
    try {
        if (getClient() != null) {
            String jst = null;
            Message msg = null;
            InputStream in = getClient().getInputStream();
            BufferedInputStream inBuf = new BufferedInputStream(in);
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            while (getClient() != null) {
                System.out.println("Receiving Data...");
                try {
                    int i;  
                    while ((i = inBuf.read()) != -1) {  
                        baos.write(i);  
                    }  
                    jst = baos.toString();
                } catch (IOException e) {
                    System.err.println("Bad Connection.");
                    stopStream();
                    break;
                }
                System.out.println(jst);
                msg = MessageFactory.fromJSON(jst);
                if (msg.getType().equals(StartMessage.defaultType)) {
                    startStream((StartMessage) msg);
                } else if (msg.getType().equals(StreamMessage.defaultType)) {
                    streaming((StreamMessage) msg);
                } else if (msg.getType().equals(
                        StopStreamMessage.defaultType)) {
                    stopStream();
                }
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
        System.err.println(e.getMessage());
    }
}

我的客户端代码是:

public void sendStart(OutputStream out) throws IOException {
    String jst = makeStart();
    out.write(jst.getBytes());
    System.out.println("data sent: " + jst);
}

当我调试它时，我看到 baos.write(i); 写入了 i 的数据。然而，数据中似乎没有 -1 所以我只能看到 jst = baos.toString(); 我终止客户端或等待时间出。

这是我得到的:

{"format":"raw","width":320,"type":"startstream","height":240}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635617","type":"image"}{"data":"[B@41635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Unexpected token LEFT BRACE({) at position 62.
    at org.json.simple.parser.JSONParser.parse(Unknown Source)
    at org.json.simple.parser.JSONParser.parse(Unknown Source)
    at org.json.simple.parser.JSONParser.parse(Unknown Source)
    at au.edu.benjamin.message.MessageFactory.fromJSON(MessageFactory.java:14)
    at au.edu.benjamin.transmission.TransListenerThread.listen(TransListenerThread.java:78)
    at au.edu.benjamin.transmission.TransListenerThread.run(TransListenerThread.java:53)
    at java.lang.Thread.run(Thread.java:745)
null
Exception in thread "Thread-2" java.lang.NullPointerException
    at au.edu.benjamin.transmission.TransListenerThread.listen(TransListenerThread.java:79)
    at au.edu.benjamin.transmission.TransListenerThread.run(TransListenerThread.java:53)
    at java.lang.Thread.run(Thread.java:745)

异常是因为意外的'{'，它应该与以前的JSON字符串分开但没有。

谁能告诉我问题出在哪里？非常感谢!

Answer 1

一旦消息结束，对 TCP 流的 ImputStream.read() 调用不会返回 -1，而是等待新字节(事实上，这样的流仅在关闭时返回 -1)。

为了实现您想要的功能，如果您不在消息的其他地方使用它，您可以在末尾使用字符串终止字符 (\0)，或者您可以在之前发送 JSON 消息的大小您自己发送并以该尺寸阅读。