Question

我基本上实现了一个向servlet发送HTTP请求的java控制台程序。此代码运行但不提供任何输出。我这里有两个问题 -

在url.openConnection（）之后，我看到了＆＃39; connected＆＃39; httpConn对象中的字段，它表示false。但如果我删除此评论

    //int responsecode = httpConn.getResponseCode();

返回状态代码200（成功）。这是什么意思？连接是否已建立？当我telnet - o localhost 8080它说＆＃39;按任意键继续＆＃39;当我这样做时，它说＆＃39;与主机失去联系＆＃39;此外，当执行上面的代码时，控制台显示此

null
null
Servlet Reached

我得到以下异常（在整个程序以调试模式运行之后）

java.net.ProtocolException: Cannot write output after reading input.

当我完成下一行代码（调试模式）时

StringBuffer requestParams = new StringBuffer();

控制台不再显示输出。究竟发生了什么？

另一个问题 - 现在我在HTTP POST消息中发送字符串作为参数但是如何发送整个对象？我必须使用序列化吗？任何帮助将非常感激。

package tutorial;

import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.net.*;
import java.util.Iterator;

class HttpUtility{

    private static HttpURLConnection httpConn;

    public static HttpURLConnection sendPostRequest(String requestURL,
            ArrayList list) throws IOException {

        URL url = new URL(requestURL);
        httpConn = (HttpURLConnection) url.openConnection();

        //int responsecode = httpConn.getResponseCode();       
        //httpConn.setDoInput(true); // true indicates the server returns response

        StringBuffer requestParams = new StringBuffer();

        if (list != null && list.size() > 0) {

            httpConn.setDoOutput(true); // true indicates POST request
            // creates the list string, encode them using URLEncoder
            Iterator iter = list.iterator();
            int index=0;

            while (iter.hasNext()) {
                String lValue = (String) iter.next();
                requestParams.append(URLEncoder.encode("params"+ index++, "UTF-8"));
                requestParams.append("=").append(
                        URLEncoder.encode(lValue, "UTF-8"));
                requestParams.append("&");
            }

            System.out.println(requestParams.toString());
            String requestParam = requestParams.toString();

            DataOutputStream wr = new DataOutputStream(httpConn.getOutputStream());
            wr.writeBytes(requestParam);
            wr.flush();
            wr.close();

            /*
            OutputStream ops = httpConn.getOutputStream();
            OutputStreamWriter writer = new OutputStreamWriter(ops);           
            writer.write(requestParams.toString());
            writer.flush();
            */

            /*
            OutputStream os = httpConn.getOutputStream();
            os.write(requestParam.getBytes());
            os.flush();
            os.close();
            */
        }

        return httpConn;
    }

    public static void disconnect() {
        if (httpConn != null) {
            httpConn.disconnect();
        }
    }
}


class ConsoleHttpRequest {

    public static String requestURL;

    public static void main(String[] args) {    

        ArrayList list = new ArrayList();

        requestURL = "http://localhost:8080/ServletTutorial/ConsoleToServlet"; // No Exception but no connection
        //requestURL = "https://localhost:8080/ServletTutorial/ConsoleToServlet"; //javax.net.ssl.SSLHandshakeException: Remote host closed connection during handshake
        //requestURL = "http://localhost"; // java.net.ConnectException: Connection refused: connect
        //requestURL="https://10.167.7.178"; // java.net.ConnectException: Connection refused: connect
        //requestURL="http://www.google.com"; // No Exception but no connection as well     

        list.add("Welcome");
        list.add("to");
        list.add("the");
        list.add("World");
        list.add("of");
        list.add("Java");
        list.add("Programming");

        try {
            HttpUtility.sendPostRequest(requestURL, list);
        } catch (IOException ex) {
            ex.printStackTrace();
        }
        HttpUtility.disconnect();
    }
}

这是从控制台程序接收请求并在控制台中打印的servlet。

package tutorial;

    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;

    /**
     * Servlet implementation class ConsoleToServlet
     */
    public class ConsoleToServlet extends HttpServlet {
        private static final long serialVersionUID = 1L;

        /**
         * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
         */
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

            String s=request.getParameter("params1");
            System.out.println(s);
            System.out.println("Servlet Reached");
        }

        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

            String s=request.getParameter("params1");
            System.out.println(s);
            doPost(request,response);
        }

    }

Answer 1

为什么在“url.openConnection（...）”之后得到'false'值

用debugtool和tcpdump **（sudo tcpdump -s 0 -A port 80）**检查后，我发现在调用openConnection时没有发送http请求头，刚开始读取输入流后，将发送来自客户端的http请求。

关于ProtocolException

如果你调用“httpConn.getResponseCode（）”，则表示http响应头被发送到客户端，因此你不能发送http请求（除非你使用http协议的“管道”功能，但它必须是服务器端也支持）

发送整个对象
试试吧：

    HttpURLConnection httpConn =(HttpURLConnection) url.openConnection();       
    httpConn.setDoOutput(true);
    ObjectOutputStream objOts=new ObjectOutputStream(httpConn.getOutputStream());
    objOts.writeObject(new Object());
    objOts.close();

想要与Servlet交互的Java Console程序

1 个答案: