HttpURLConnection没有返回所有标头

时间:2016-10-03 18:30:30

标签: java httpurlconnection

我正在使用以下代码打印HTTP标头。

    URL url = new Url("htttp://example.com/example");
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();

    Map<String, List<String>> map = conn.getHeaderFields();
    for (Map.Entry<String, List<String>> entry : map.entrySet()) {
        System.out.println("Key : " + entry.getKey() +
                " ,Value : " + entry.getValue());
    }

这是输出:

Key : null ,Value : [HTTP/1.1 200 OK]
Key : Accept-Ranges ,Value : [bytes]
Key : Cache-Control ,Value : [max-age=604800, public]
Key : Connection ,Value : [Keep-Alive]
Key : Date ,Value : [Mon, 03 Oct 2016 18:01:06 GMT]
Key : ETag ,Value : ["159eb4-53dce1f957880-gzip"]
Key : Expires ,Value : [Mon, 10 Oct 2016 18:01:06 GMT]
Key : Keep-Alive ,Value : [timeout=5, max=100]
Key : Last-Modified ,Value : [Sat, 01 Oct 2016 13:59:46 GMT]
Key : Server ,Value : [Apache/2.4.12 (Unix) OpenSSL/1.0.1e-fips mod_bwlimited/1.4]
Key : Transfer-Encoding ,Value : [chunked]
Key : Vary ,Value : [Accept-Encoding,User-Agent]

现在我正在尝试通过curl:

$ curl -v -D - http://example.com/example -o /dev/null
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0*   Trying 111.111.111.111...
  0     0    0     0    0     0      0      0 --:--:--  0:00:01 --:--:--     0* Connected to example.com (111.111.111.111) port 80 (#0)
> GET example.com/example HTTP/1.1
> Host: example.com
> User-Agent: curl/7.47.0
> Accept: */*
> 
< HTTP/1.1 200 OK
HTTP/1.1 200 OK
< Date: Mon, 03 Oct 2016 18:25:11 GMT
Date: Mon, 03 Oct 2016 18:25:11 GMT
< Server: Apache/2.4.12 (Unix) OpenSSL/1.0.1e-fips mod_bwlimited/1.4
Server: Apache/2.4.12 (Unix) OpenSSL/1.0.1e-fips mod_bwlimited/1.4
< Last-Modified: Sat, 01 Oct 2016 13:59:46 GMT
Last-Modified: Sat, 01 Oct 2016 13:59:46 GMT
< ETag: "159eb4-53dce1f957880"
ETag: "159eb4-53dce1f957880"
< Accept-Ranges: bytes
Accept-Ranges: bytes
< Content-Length: 1416884
Content-Length: 1416884
< Cache-Control: max-age=604800, public
Cache-Control: max-age=604800, public
< Expires: Mon, 10 Oct 2016 18:25:11 GMT
Expires: Mon, 10 Oct 2016 18:25:11 GMT
< Vary: Accept-Encoding,User-Agent
Vary: Accept-Encoding,User-Agent

< 
{ [1080 bytes data]
 30 1383k   30  427k    0     0   116k      0  0:00:11  0:00:03  0:00:08  116k^C

查看java输出中缺少Content-Length标头的方式?为什么会这样?我该如何解决这个问题?

3 个答案:

答案 0 :(得分:4)

Content-Length丢失,因为服务器以块的形式发送了响应。这是预期的行为。查看Java响应中的Transfer-Encoding标头,这里是RFC 2616, 4.4 Message Length(参见列表的第3项)。

答案 1 :(得分:2)

&#39;内容长度&#39;自动解析,可以通过conn.getContentLength()conn.getContentLengthLong()检索。有关详细信息,请参阅https://docs.oracle.com/javase/7/docs/api/java/net/URLConnection.html#getContentLengthLong()

答案 2 :(得分:0)

java中的响应包括&#39; transfer-encoding&#39;在卷曲响应的情况下丢失的标题。此外,当我尝试它时,我得到了404(未找到)我的尝试。当我从浏览器中尝试时,我得到了404。

我的猜测是你有一个被覆盖的example.com主机条目,它会循环回你自己的tomcat或者类似的东西。这是您的环境问题。

这就是我得到的:

    /**
     *
     * <P> jdk-1.8 </P>
     * <PRE>
Key :null || Values :[HTTP/1.1 404 Not Found]
Key :X-Cache || Values :[HIT]
Key :Server || Values :[ECS (ewr/1445)]
Key :Etag || Values :["359670651+gzip+ident"]
Key :Cache-Control || Values :[max-age=604800]
Key :x-ec-custom-error || Values :[1]
Key :Vary || Values :[Accept-Encoding]
Key :Last-Modified || Values :[Fri, 09 Aug 2013 23:54:35 GMT]
Key :Expires || Values :[Mon, 10 Oct 2016 19:20:29 GMT]
Key :Content-Length || Values :[1270]
Key :Date || Values :[Mon, 03 Oct 2016 19:20:29 GMT]
Key :Content-Type || Values :[text/html]
     * </PRE>
     * @param urlStr (http://example.com/example)
     */
    private static void printHeaders(String urlStr) {

        try {
            URL urlRef = new URL(urlStr);
            URLConnection urlConnection = urlRef.openConnection();
            Map<String, List<String>> headerFields = urlConnection.getHeaderFields();

            for (String headerName : headerFields.keySet()) {
                List<String> headerEntry = headerFields.get(headerName);
                System.out.println("Key :"+headerName +" || Values :"+headerEntry);
            }
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }