HttpURLConnection getInputStream读取页面,然后发出POST请求

Question

我试图获取页面(HTML),从中读取特殊令牌(每次都不同),然后发送POST请求,但这给了我 java.lang.IllegalStateException: connect in progress

    final URL url = new URL("<...>");
    String token = null;
    final HttpURLConnection con = (HttpURLConnection) url.openConnection();
    try (final InputStreamReader isr = new InputStreamReader(con.getInputStream())) {
        try (final BufferedReader in = new BufferedReader(isr)) {
            String str;
            while ((str = in.readLine()) != null) {
                if (str.contains("__token")) {
                    token = str.replace("<...>", "").replace("<...>", "");
                    System.out.println(token);
                    break;
                }
            }
            in.close();
        }
        isr.close();
    }
    con.setRequestMethod("POST");
    con.setRequestProperty("User-Agent", USER_AGENT);
    con.setDoOutput(true);
    try (final DataOutputStream wr = new DataOutputStream(con.getOutputStream())) {
        final String params = getParams("par1", "par2", token);
        wr.writeBytes(params);
        wr.flush(); wr.close();
        final int responseCode = con.getResponseCode();
        System.out.println("\nSending 'POST' request to URL : " + url);
        System.out.println("Post parameters : " + params);
        System.out.println("Response Code : " + responseCode);
        try (final BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()))) {
            String inputLine;
            final StringBuilder response = new StringBuilder();
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();
            System.out.println(response.toString());
        }
    }

如果我尝试从cookie中获取此令牌,那么同样如此:

final String token=con.getHeaderField("Set-Cookie").replace("__Token=", "").replace("; path=/; HttpOnly", "");

怎么做得好？

Answer 1

该文件HttpURLConnection说:

每个HttpURLConnection实例用于发出单个请求,但是与HTTP服务器的基础网络连接可以由其他实例透明地共享.

这意味着您无法在同一HttpURLConnection对象上创建新的(POST)请求.事实上,你得到了一个IllegalStateException.

因此,您应该final从定义中删除修饰符con,然后在完成对原始(GET)请求的输出的处理之后,创建另一个连接:

con = (HttpURLConnection) url.openConnection();

只有这样,您才能继续构建POST请求.

一点注意事项:您使用try-with-resources,因此您无需显式关闭流.此外,您不需要两个try块.实际上,您不需要保持对引用的引用InputStreamReader,因为BufferedReader.close()也会关闭底层Reader,这也会关闭底层InputStream.