Question

我是Java新手。我写了一个带有gui的applet，它将结果（int w和int p）发送到服务器，我得到“411 Length Required”错误。我究竟做错了什么？你如何设置内容长度？

这是与服务器通信的方法：

public void sendPoints1(int w, int p){

    try {
        String url = "http://somename.com:309/api/Results";
        String charset = "UTF-8";
        String query = String.format("?key=%s&value=%s",
            URLEncoder.encode(String.valueOf(w), charset),
            URLEncoder.encode(String.valueOf(p), charset));
        String length = String.valueOf((url + query).getBytes("UTF-8").length);

        HttpURLConnection connection = (HttpURLConnection) new URL(url + query).openConnection();
        connection.setRequestMethod("POST");
        connection.setRequestProperty("Content-Length", length);
        connection.connect();
        System.out.println("Responce Code:    " + connection.getResponseCode());
        System.out.println("Responce Message: " + connection.getResponseMessage());
    } catch (Exception e) {
        System.err.println(e.getMessage());
    }

}

Answer 1

我不是100％肯定你为什么会收到411错误代码，但这可能与你没有发送任何内容的事实有关。 content-length头应该是请求主体的字节长度。您将其设置为网址的长度！

将请求更改为GET或将查询放入请求正文而不是URL本身。如果您执行后者，请将content-length设置为正文的长度。

public void sendPoints1(int w, int p){

    try {
        String url = "http://somename.com:309/api/Results";
        String charset = "UTF-8";
        String query = String.format("key=%s&value=%s",
            URLEncoder.encode(String.valueOf(w), charset),
            URLEncoder.encode(String.valueOf(p), charset));
        byte[] queryBytes = query.getBytes("UTF-8");
        String length = String.valueOf((url + query).getBytes("UTF-8").length);

        HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
        connection.setRequestMethod("POST");
        connection.setRequestProperty("Content-Length", length);
        OutputStream os = connection.getOutputStream();
        os.write(queryBytes);
        os.flush();
        connection.connect();
        System.out.println("Responce Code:    " + connection.getResponseCode());
        System.out.println("Responce Message: " + connection.getResponseMessage());
    } catch (Exception e) {
        System.err.println(e.getMessage());
    }

}

Answer 2

请求uri包含查询，可以使用GET方法。

connection.setRequestMethod("POST"); // modify to GET
connection.setRequestProperty("Content-Length", length); //remove the line

如果使用POST方法，包含'content-length'标题，必须发送数据。

例如：

public void sendPoints1(int w, int p){

    try {
        String url = "http://somename.com:309/api/Results";
        //value type is int ,don't need URLEncoder.
        byte[] data = ("key="+w+"&value="+p).getBytes("UTF-8");

        HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
        connection.setRequestMethod("POST");
        connection.setRequestProperty("Content-Length", data.length);
 connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); //URLencode...
        OuptputStream out = connection.getOutputStream();
        out.write(data);
        out.flush();
        InputStream in = connnection.getInputStream();
        //read .....
        System.out.println("Responce Code:    " + connection.getResponseCode());
        System.out.println("Responce Message: " + connection.getResponseMessage());
    } catch (Exception e) {
        System.err.println(e.getMessage());
    }

}

Answer 3

由于所有信息都作为URL的一部分作为查询字符串传递，因此您需要不 setRequestMethod 作为 POST 。但是如果您仍然希望将其设置为POST作为逻辑的一部分，则 setRequestProperty（“Content-Length”，“0”），因为Http Server期望在调用POST方法时读取Length。在你的情况下，没有任何内容被写为POST信息，所以最好将其设置为ZERO，甚至认为默认值为ZERO有时服务器可能会给出响应errorCode为411，响应消息：所需长度

Java Applet 411内容长度

3 个答案: