Question

我正在尝试在Java EE 7中创建一个Websocket端点，它接收文件名作为输入并返回图像的二进制数据。这是Websocket的Java端：

@ServerEndpoint(value = "/hellobinary")

public class HelloWorldBinaryEndpoint {

@OnMessage   
public void hello(String img, Session session) {

    File fi = new File("C:\\Users\\\images\\"+img);
    byte[] fileContent=null;
    try {
        fileContent = Files.readAllBytes(fi.toPath());
        ByteBuffer buf = ByteBuffer.wrap(fileContent);

        session.getBasicRemote().sendBinary(buf);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}

这是它的Javascript方面：

        var wsUri = "ws://localhost:8080/websocket/hellobinary";

        function init() {
            output = document.getElementById("output");
        }
        function send_message() {
            websocket = new WebSocket(wsUri);
            websocket.onopen = function(evt) {
                onOpen(evt)
            };
            websocket.onmessage = function(evt) {
                onMessage(evt)
            };
            websocket.onerror = function(evt) {
                onError(evt)
            };
        }
        function onOpen(evt) {
            writeToScreen("Connected to Endpoint!");
            doSend(textID.value);
        }
        function onMessage(evt) {

            drawImageBinary(evt.data);
        }
        function onError(evt) {
            writeToScreen('<span style="color: red;">ERROR:</span> ' + evt.data);
        }
        function doSend(message) {
            writeToScreen("Message Sent: " + message);
            websocket.send(message);

        }
        function writeToScreen(message) {
            var pre = document.createElement("p");
            pre.style.wordWrap = "break-word";
            pre.innerHTML = message;

            output.appendChild(pre);
        }
        function drawImageBinary(blob) {
            var bytes = new Uint8Array(blob);
            alert('received '+ bytes.length);
            var imageData = context.createImageData(canvas.width, canvas.height);

            for (var i=8; i<imageData.data.length; i++) {
                imageData.data[i] = bytes[i];
            }
            context.putImageData(imageData, 0, 0);

            var img = document.createElement('img');
            img.height = canvas.height;
            img.width = canvas.width;
            img.src = canvas.toDataURL();
        }
        window.addEventListener("load", init, false);

由于从Java端正确读取了图像（至少读取的字节数是正确的），我认为问题出在JavaScript端。
我添加了一个警报来记录drawImageBinary中读取的字节数，但是打印“0”并且屏幕上没有任何内容呈现。有人能找到罪魁祸首吗？谢谢！

Answer 1

客户端缺少：

websocket.binaryType =“arraybuffer”;

使用Websockets从Java端点发送映像

1 个答案: