Question

我们如何在HttpServletResponse中获取内容类型，服务器等的http响应头？需要获得所有可用的标题。

当我们使用UrlConnection的openConnection并使用getHeaderFields时，我们会得到所有这些标题。但是当我们将getHeaderNames与HttpServletResponse一起使用时，我们没有得到这样的标题。

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

    Enumeration<String> requestHeaders = request.getHeaderNames();
    while(requestHeaders.hasMoreElements())
    {

        String header = requestHeaders.nextElement();
        System.out.println("request headerrrrrrr>>" + header);
    }

    Collection<String> responseHeaders = response.getHeaderNames();
    Iterator<String> it = responseHeaders.iterator();
    while(it.hasNext()){
        String header = it.next();
        System.out.println("response headerrrrrr>>" + header);
    }

    response.getWriter().append("Served at: ").append(request.getContextPath());
}

在chrome开发人员工具中，我可以看到下面的

General

Request URL:http://localhost:8080/TestWebApp/MyTestServlet
Request Method:GET
Status Code:200 OK
Remote Address:[::1]:8080

Response Headers

Content-Length:22
Date:Fri, 03 Mar 2017 07:40:56 GMT
Server:Apache-Coyote/1.1

Request Headers

Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Encoding:gzip, deflate, sdch, br
Accept-Language:en-US,en;q=0.8
Connection:keep-alive
Cookie:JSESSIONID=DF62FC092F67FBB02AF68BC646085065; ai_user=MKfG+|2017-03-02T10:44:54.721Z; _ga=GA1.1.1362801303.1488451499
Host:localhost:8080
Upgrade-Insecure-Requests:1
User-Agent:Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36

但是控制台输出只是请求标头

request headerrrrrrr>>host
request headerrrrrrr>>connection
request headerrrrrrr>>upgrade-insecure-requests
request headerrrrrrr>>user-agent
request headerrrrrrr>>accept
request headerrrrrrr>>accept-encoding
request headerrrrrrr>>accept-language
request headerrrrrrr>>cookie

我在Log only http servlet response headers的BalusC回答提及中提到过。但似乎没有像我需要的那样工作

使用doFilter方法创建一个过滤器，如下所示

public void doFilter(ServletRequest request, final ServletResponse response, FilterChain chain) throws IOException, ServletException {

    DOMConfigurator.configure("C:\\log4j.xml");

    Logger logger = Logger.getLogger(TestFilter.class);
    logger.info("do Filter TestFilter");
    final Map<String, List<String>> headers = new HashMap<String, List<String>>();

    chain.doFilter(request, new HttpServletResponseWrapper((HttpServletResponse) response) {
        @Override public void setHeader(String name, String value) {
            List<String> values = new ArrayList<String>();
            values.add(value);
            headers.put(name, values);
            super.setHeader(name, value);
        }

        @Override public void addHeader(String name, String value) {
            List<String> values = headers.get(name);
            if (values == null) {
            values = new ArrayList<String>(); 
            headers.put(name, values);
            }
            values.add(value);
            super.addHeader(name, value);
        }
    });

    logger.info("headers size>>"+headers.size());
    logger.info("these are the headers>>"+headers);

}

控制台日志

INFO    2017-03-03 05:14:23,765 [http-bio-8080-exec-3] com.test.TestFilter  - do Filter TestFilter
INFO    2017-03-03 05:14:23,768 [http-bio-8080-exec-3] com.test.TestFilter  - headers size>>0
INFO    2017-03-03 05:14:23,768 [http-bio-8080-exec-3] com.test.TestFilter  - these are the headers>>{}

也许我错过了什么？

Answer 1

正如在评论中所说，servlet负责在响应每个http请求时生成标头。

标题基本上用于在客户端和服务器之间创建对话。

获取示例

客户端：给我/ MyTestServlet对象，我希望它是一个html页面。如果它被压缩它会更好，但如果不是它也没关系。

Accept: text/html,application/xhtml+xml
Accept-Encoding: gzip, deflate

服务器：好的，我在charset iso-8859-1中发送了一个html，抱歉它没有按照您的要求压缩，长度为9639字节，最后一次修改是在2月13日.BTW ，我是“MySuperServer”。

Content-Type: text/html
Content-Length: 9639
Last-Modified: Mon, 13 Feb 2017 12:47:56 GMT
Server: MySuperServer

这个GET的代码是：

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

    String contentType = request.getHeader("Accept");
    if (contentType.contains("text/html") || contentType.contains("*/*")) {
        // the client expects for a web page (or anything), so let's send it
        String page = createSomehowPage();
        response.addHeader("Content-Type", "text/html");
        response.addHeader("Content-Length", String.valueOf(page.length()));
        response.addHeader("Last-Modified", "Mon, 13 Feb 2017 14:42:56 GMT");
        response.addHeader("Server", "MySuperServer");
        response.getWriter().append(page);
        response.setStatus(200);
    } else {
        response.addHeader("Server", "MySuperServer");
        response.getWriter().append("Sorry, I don't serve the content-Type '").append(contentType).append("' you asked");
        response.setStatus(406); // 406=Not Acceptable
    }
}

您可以在HTTP Headers中找到更多信息。

修改

Tomcat会自动设置标头：

Server：Tomcat Coyote使用Protocol's Server header definition设置的强制标题（请参阅server.xml configuration）（请参阅“服务器”部分）。

Date :(见Protocol's Date header definition）

Content-Length :(见discussion about it）

为了记录Tomcat中的所有标题，您应该考虑this answer，基本上说：


将AccessLogValve放在Host或Context元素中，例如：


<Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="mysitelog." suffix=".txt" pattern="..." resolveHosts="false" />

Servlet或Filter或Listener中的HttpResponse标头

1 个答案: