socket http request to tomcat, but response 302

Question

when I use Postman to get result using url : "localhost:8080/examples", and I can get the correct result :

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<!DOCTYPE HTML>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Apache Tomcat Examples</title>
    </head>
    <body>
        <p>
            <h3>Apache Tomcat Examples
            </H3>
            <p></p>
            <ul>
                <li>
                    <a href="servlets">Servlets examples</a>
                </li>
                <li>
                    <a href="jsp">JSP Examples</a>
                </li>
                <li>
                    <a href="websocket/index.xhtml">WebSocket Examples</a>
                </li>
            </ul>
        </body>
    </html>

tomcat version : 8.5.32

but when I use socket to get result from tomcat server, then the result confuse me. Code is here :


public void httpTest(){

        Socket socket = new Socket("localhost", 8080);
        data = "GET /examples HTTP/1.1\n" +
                "Host: localhost:8080\n" +
                "Cache-Control: no-cache\n" +
                "Postman-Token: 60236fcd-995c-49d9-896c-f88a1bdfbfd3\n\n".getBytes();

        log.debug("receive http request :\r\n{}", new String(data));


        try {

            //向服务器端发送数据
            DataOutputStream out = new DataOutputStream(socket.getOutputStream());
            out.write(data);
            out.flush();

            //读取服务器端数据
            DataInputStream input = new DataInputStream(socket.getInputStream());
            byte[] result = readStream(input);

            log.debug("receive response :\r\n{}", new String(result));
            input.close();
            out.close();

            return result;
        } catch (Exception e) {
            log.error("请求本地服务数据异常, ", e);
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e2) {
                    socket = null;
                    log.error("客户端关闭socket异常, " ,e);
                }
            }
            socket = null;
            return _404();
        }
}

the code result log is here :

[DEBUG] 2019-09-01 16:50:08,304 method:com.jasey.reverse.client.core.local.LocalHostSender.send(LocalHostSender.java:18)
receive http request :
GET /examples HTTP/1.1
Host: localhost:8080
Cache-Control: no-cache
Postman-Token: 60236fcd-995c-49d9-896c-f88a1bdfbfd3


[DEBUG] 2019-09-01 16:50:28,364 method:com.jasey.reverse.client.core.local.LocalHostSender.send(LocalHostSender.java:37)
receive response :
HTTP/1.1 302 
Location: /examples/
Transfer-Encoding: chunked
Date: Sun, 01 Sep 2019 08:50:08 GMT

0


HTTP/1.1 302 
Location: /examples/
Transfer-Encoding: chunked
Date: Sun, 01 Sep 2019 08:50:08 GMT

0

I don't known why, please help me

302 indicates a redirect response. Just follow the redirect. — Henry, Sep 01 '19 at 09:07
Most probably because Postman automatically follows the redirect and makes a second request to /examples/ without you noticing it. If you want to do the same thing as Postman, follow the redirect too, i.e. read the Location header in the response, and send a second GET request to that location. Or use an actual HTTP client library that will do that for you. — JB Nizet, Sep 01 '19 at 09:07

score 1 · Answer 1 · answered Sep 01 '19 at 09:35

1

Response code 302 means Redirect. Postman probably follows it, giving you the result.

The simplest thing in these cases, in my opinion, is to make the request using a simple library like Apache HttpClient.

Here is a useful tutorial for learn HttpClient library: https://www.tutorialspoint.com/apache_httpclient/index.htm

Here how to automatically follow the redirects: Handling HttpClient Redirects

answered Sep 01 '19 at 09:35

lorenzo

627
8
12

1

Everybody loves the Apache httpd-client library for some reason, but I find it to be much more complicated than just using the built-in `java.net.HttpURLConnection`. But either way, you are better off using a component that understands HTTP instead of using a bare socket for communications. – Christopher Schultz Sep 04 '19 at 13:28

socket http request to tomcat, but response 302

1 Answers1