Several common ways to get requested URL address in Java

1. Get it in Servlet

import ;
import ;
import ;
import ;
 
public class UrlDemoServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) 
            throws IOException {
        // Get a similar ":8080/app/path/to/servlet"        StringBuffer url = ();
 
        // If you want the query string after the question mark, such as "?a=1&b=2"        String queryString = (); // May be null 
        String fullUrl = (queryString == null) 
            ? () 
            : ('?').append(queryString).toString();
 
        ().write("Full URL: " + fullUrl);
    }
}

()returnStringBuffer, including protocol, server name, port, context path, and servlet path.
()Return to URL?The latter part (excluding?self), if there are no query parameters, it isnull。

2. Get it in Spring MVC controller

import ;
import ;
import ;
import ;
 
@Controller
public class UrlDemoController {
 
    @GetMapping("/demo")
    @ResponseBody
    public String demo(HttpServletRequest request) {
        StringBuffer url = ();
        String qs  = ();
        return (qs == null) ? () : ('?').append(qs).toString();
    }
}

Spring will automaticallyHttpServletRequestInjected into method parameters, the usage is the same as that of Servlet.

3. Get it in the filter (Filter)

import .*;
import ;
import ;
 
public class UrlLoggingFilter implements Filter {
    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
            throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        StringBuffer url = ();
        String qs  = ();
        String fullUrl = (qs == null) ? () : ('?').append(qs).toString();
        ("Incoming request URL: " + fullUrl);
        (req, res);
    }
}

Filters are often used for log printing, authentication, and unified processing.

4. Get more detailed parts

():protocol(httporhttps）
(): Hostname or IP
(): Port number
(): Application context path (depending on deploymentappname)
(): Servlet map path
(): Additional path information
(): Query string (excluding?）

If you need to get the original requested host name and protocol after the reverse proxy (Nginx, F5), you must combine itX-Forwarded-Proto / X-Forwarded-HostWait for the head to reorganize:

String proto = ("X-Forwarded-Proto");
if (proto == null) proto = ();
 
String host  = ("X-Forwarded-Host");
if (host == null) host = ();
 
String port  = ("X-Forwarded-Port");
if (port == null) port = (());
 
String fullUrl = proto + "://" + host + (() ? "" : ":" + port)
               + ()
               + (qs == null ? "" : "?" + qs);

5. Client (HTTP client library) get request URL

If you are in the client code (such as using Apache HttpClient, OkHttp) you want to get the request URL you sent:

Apache HttpClient

HttpGet get = new HttpGet("/data?x=1");
(());  // Output URI Object

OkHttp

Request req = new ()
    .url("/data?x=1")
    .build();
(());  //  Object

The above is the method of "Java: Get Request URL Address" in various common scenarios, just choose as needed.

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