Question

看看这些代码：

public static String get(String url, Properties parameters) throws MalformedURLException, IOException{
        url = buldGetUrl(url, parameters);
        if(DEBUG) System.out.println("[HTTP GET REQUEST]");
        if(DEBUG) System.out.println(" URL: " + url);
        HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection();
        conn.setRequestProperty("Cookie","JSESSIONID=" + J_SESSION_ID);
        conn.connect();

        if(DEBUG) System.out.println("\n[HTTP GET RESPONSE]");
        if(DEBUG) System.out.println("==== Response Headers =====");
        String serverCookies = conn.getHeaderField("Set-Cookie");
        if(serverCookies != null){
            String[] cookies = serverCookies.split(";");
            for(String s : cookies){
                s = s.trim();
                if(s.split("=")[0].equals("JSESSIONID")){
                    J_SESSION_ID = s.split("=")[1];
                    if(DEBUG) System.out.println(" Session ID Found: " + J_SESSION_ID);
                    break;
                }
            }
        }
        if(DEBUG){
            for(String s : conn.getHeaderFields().keySet()){
                if(s == null)
                    System.out.println(" " + conn.getHeaderField(s));
                else
                    System.out.println(" " + s + "=" + conn.getHeaderField(s));
            }
        }

        if(DEBUG) System.out.println("==== Response Content =====");
        BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        String str = null;
        StringBuilder sb = new StringBuilder();
        while ((str = br.readLine()) != null) {
            sb.append(str + System.getProperty("line.separator"));
            if(DEBUG) System.out.println(str);

        }
        br.close();
        return sb.toString();
    }

请注意以下三行：

HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection();    
conn.setRequestProperty("Cookie","JSESSIONID=" + J_SESSION_ID);
conn.connect();

网址#openConnection 和网址#connect ，哪种方法将请求发送给服务器？如果答案是 openConnection 方法，如何在请求已经发送后设置cookie？如果答案是连接方法，你猜怎么着？这些代码也可以，我可以从服务器获得响应：

url = buldGetUrl(url, parameters);
        if(DEBUG) System.out.println("[HTTP GET REQUEST]");
        if(DEBUG) System.out.println(" URL: " + url);
        HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection();

        if(DEBUG) System.out.println("\n[HTTP GET RESPONSE]");
        if(DEBUG) System.out.println("==== Response Headers =====");
        String serverCookies = conn.getHeaderField("Set-Cookie");
        if(serverCookies != null){
            String[] cookies = serverCookies.split(";");
            for(String s : cookies){
                s = s.trim();
                if(s.split("=")[0].equals("JSESSIONID")){
                    J_SESSION_ID = s.split("=")[1];
                    if(DEBUG) System.out.println(" Session ID Found: " + J_SESSION_ID);
                    break;
                }
            }
        }
        if(DEBUG){
            for(String s : conn.getHeaderFields().keySet()){
                if(s == null)
                    System.out.println(" " + conn.getHeaderField(s));
                else
                    System.out.println(" " + s + "=" + conn.getHeaderField(s));
            }
        }

        if(DEBUG) System.out.println("==== Response Content =====");
        BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        String str = null;
        StringBuilder sb = new StringBuilder();
        while ((str = br.readLine()) != null) {
            sb.append(str + System.getProperty("line.separator"));
            if(DEBUG) System.out.println(str);

        }
        br.close();
        return sb.toString();

Answer 1

方法connect（）将打开与此URL引用的资源的通信链接（如果尚未建立此连接）。 getInputStream（），getResponseCode（）或getResponseMessage（）方法将创建与服务器的通信链接

Answer 2

一般来说，＃connect（）实际上是多余的，只要这个HttpURLConnection类的方法，即检索响应信息（例如#getInputStream（）/ getResponseCode（）/ getHeaderFields（）/ etc）。，被调用，实际上将完成隐式连接。我是对的吗？

我的理解基于以下讨论： Using java.net.URLConnection to fire and handle HTTP requests

用Java在HttpURLConnection中设置cookie的时间是什么时候？

2 个答案: