How to get host name with port from a http or http

问题:

I have two applications deployed in jboss container(same unix box). If i get a request from app1, i need to frame a corresponding request for app2.

eg:
if app1 request is: http://example.com/context?param1=123
then I need to extract "http://example.com/", so that I can frame request for second app.

I tried using:

  HttpServletRequest.getServerName() & 
  HttpServletRequest.getServerPort() & \
  HttpServletRequest.getHeader("host") 

methods, but the request may be of http or https.

Please let me know if there is any other better way. Thanks!

回答1:

You can use HttpServletRequest.getScheme() to retrieve either "http" or "https".

Using it along with HttpServletRequest.getServerName() should be enough to rebuild the portion of the URL you need.

You don't need to explicitly put the port in the URL if you're using the standard ones (80 for http and 443 for https).

Edit: If your servlet container is behind a reverse proxy or load balancer that terminates the SSL, it's a bit trickier because the requests are forwarded to the servlet container as plain http. You have a few options:

1) Use HttpServletRequest.getHeader("x-forwarded-proto") instead; this only works if your load balancer sets the header correctly (Apache should afaik).

2) Configure a RemoteIpValve in JBoss/Tomcat that will make getScheme() work as expected. Again, this will only work if the load balancer sets the correct headers.

3) If the above don't work, you could configure two different connectors in Tomcat/JBoss, one for http and one for https, as described in this article.

回答2:

You can use HttpServletRequest.getRequestURL and HttpServletRequest.getRequestURI.

StringBuffer url = request.getRequestURL();
String uri = request.getRequestURI();
String host = url.substring(0, url.indexOf(uri)); //result

回答3:

If you want the original URL just use the method as described by jthalborn. If you want to rebuild the url do like David Levesque explained, here is a code snippet for it:

final javax.servlet.http.HttpServletRequest req = (javax.servlet.http.HttpServletRequest) ...;
final int serverPort = req.getServerPort();
if ((serverPort == 80) || (serverPort == 443)) {
  // No need to add the server port for standard HTTP and HTTPS ports, the scheme will help determine it.
  url = String.format("%s://%s/...", req.getScheme(), req.getServerName(), ...);
} else {
  url = String.format("%s://%s:%s...", req.getScheme(), req.getServerName(), serverPort, ...);
}

You still need to consider the case of a reverse-proxy:

• request.getScheme() is returning http instead of returning https in java

Could use constants for the ports but not sure if there is a reliable source for them, default ports:

• Are HTTP and HTTPS default port numbers defined in the JDK?

Most developers will know about port 80 and 443 anyways, so constants are not that helpful.

Also see this similar post.

回答4:

If you use the load balancer & Nginx, config them without modify code.

Nginx:

proxy_set_header       Host $host;  
proxy_set_header  X-Real-IP  $remote_addr;  
proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;  
proxy_set_header X-Forwarded-Proto  $scheme;  

Tomcat's server.xml Engine:

<Valve className="org.apache.catalina.valves.RemoteIpValve"  
remoteIpHeader="X-Forwarded-For"  
protocolHeader="X-Forwarded-Proto"  
protocolHeaderHttpsValue="https"/> 

If only modify Nginx config file, the java code should be:

String XForwardedProto = request.getHeader("X-Forwarded-Proto");

回答5:

Refer to http://docs.oracle.com/javase/tutorial/networking/urls/urlInfo.html . This is the most concise coverage on url parsing.

回答6:

If your server is running behind a proxy server, make sure your proxy header is set:

proxy_set_header X-Forwarded-Proto  $scheme;

Then to get the right scheme & url you can use springframework's classes:

public String getUrl(HttpServletRequest request) {
    HttpRequest httpRequest = new ServletServerHttpRequest(request);
    UriComponents uriComponents = UriComponentsBuilder.fromHttpRequest(httpRequest).build();

    String scheme = uriComponents.getScheme();             // http / https
    String serverName = request.getServerName();     // hostname.com
    int serverPort = request.getServerPort();        // 80
    String contextPath = request.getContextPath();   // /app

    // Reconstruct original requesting URL
    StringBuilder url = new StringBuilder();
    url.append(scheme).append("://");
    url.append(serverName);

    if (serverPort != 80 && serverPort != 443) {
        url.append(":").append(serverPort);
    }
    url.append(contextPath);
    return url.toString();
}