httpurlconnection 非法状态异常：已连接

Question

我正在尝试 post 参数并从输入流中读取重定向页面，但我对这个异常一无所知

Exception in thread "main" java.lang.IllegalStateException: Already connected
    at java.net.URLConnection.setDoOutput(URLConnection.java:900)
    at sun.net.www.protocol.https.HttpsURLConnectionImpl.setDoOutput(HttpsURLConnectionImpl.java:455)
    at com.company.Main.main(Main.java:58)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

代码：

try {

        CookieHandler cookieHandler = null;
        CookieManager.setDefault(cookieHandler);


        HttpURLConnection urlConnection = (HttpURLConnection) new URL("site").openConnection();
        InputStream i = new BufferedInputStream(urlConnection.getInputStream());
        StringBuilder stringBuilder =new StringBuilder();


        int c;
        while ((c=i.read())!=-1){
            stringBuilder.append((char)c);
        }

         // for getting the post paramters that is user name and password field
        Pattern p = Pattern.compile("<input name=\"\w{22}\" type=\"text\" id=\"\w{22}\" />");
        Matcher matcher = p.matcher(stringBuilder.toString());

        String user_name = null;
        while (matcher.find()){

            user_name = matcher.group().split("\"")[1];

        }

        String password = null;
        p= Pattern.compile("<input name=\"\w{22}\" type=\"password\" id=\"\w{22}\" />");
        matcher= p.matcher(stringBuilder.toString());
        while (matcher.find()){

            password = matcher.group().split("\"")[1];

        }
        System.out.print(user_name + "  "  + password);



        String urlParameters  = user_name+"=xyz&"+password+"=xyz";
        byte[] postData       = urlParameters.getBytes( StandardCharsets.UTF_8 );
        int    postDataLength = postData.length;

        urlConnection.setDoOutput(true);
        urlConnection.setDoInput(true);
        urlConnection.setRequestMethod("POST");
        urlConnection.setRequestMethod(Integer.toString(postDataLength));


        Writer writer = new BufferedWriter(new OutputStreamWriter(urlConnection.getOutputStream()));
        writer.write(urlParameters);
        writer.flush();

        urlConnection.setDoInput(true);
        urlConnection.getContent();

        while ((c=i.read())!=-1){
            System.out.print((char)c);

        }


    } catch (IOException e) {
        e.printStackTrace();
    }

Answer 1

您需要调用 urlConnection.setDoInput(true)、urlConnection.setDoOutput(true)、urlConnection.setRequestMethod("POST")、urlConnection.setRequestMethod(Integer.toString(postDataLength)) 以及任何其他在调用 urlConnection.getInputStream() 和 urlConnection.getOutputStream() 因为这些方法实际上会启动请求，所以一旦调用修改请求就太晚了，这就是你得到这个 Exception.

的原因

响应更新

您实际面临的主要问题是您想要重用 HttpURLConnection 而它并不意味着要重用，这就是为什么您会收到此异常，您需要创建每个 HTTP 请求一个新的 HttpURLConnection。

httpurlconnection 非法状态异常：已连接

httpurlconnection illegal state exception : already connected

java

httpurlconnection