Class ViaRequest

java.lang.Object

org.apache.hc.core5.http.protocol.ViaRequest

All Implemented Interfaces:

HttpRequestInterceptor

@Contract(threading=IMMUTABLE)
public class ViaRequest
extends Object
implements HttpRequestInterceptor

This request interceptor can be used by an HTTP proxy or intemediary to add the HttpHeaders.VIA HTTP header to outgoing request messages.

The HttpHeaders.VIA header is used to indicate intermediate protocols and recipients between the user agent and the server (on requests) or between the origin server and the client (on responses). It can be used for tracking message forwards, avoiding request loops, and identifying the protocol capabilities of senders along the request/response chain. Each member of the HttpHeaders.VIA header field value represents a proxy or gateway that has forwarded the message.

A proxy MUST send an appropriate HttpHeaders.VIA header field, as described in the HTTP specification, in each message that it forwards. An HTTP-to-HTTP gateway MUST send an appropriate HttpHeaders.VIA header field in each inbound request message and MAY send a HttpHeaders.VIA header field in forwarded response messages.

This interceptor ensures that the HttpHeaders.VIA header is added to the request only if it has not been added previously, as per the HTTP specification. Additionally, it updates the values in the HttpHeaders.VIA header correctly in case of multiple intermediate protocols or recipients, by appending its own information about how the message was received to the end of the header field value.

Since:

5.3

Field Summary

Fields

Modifier and Type	Field	Description
static final HttpRequestInterceptor	INSTANCE	Singleton instance.

Constructor Summary

Constructors

Constructor	Description
ViaRequest()	Constructs a new ViaRequest.

Method Summary

Modifier and Type	Method	Description
void	process(HttpRequest request, EntityDetails entity, HttpContext context)	Adds the HTTP HttpHeaders.VIA header to the request if it does not already exist.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

INSTANCE

public static final HttpRequestInterceptor INSTANCE

Singleton instance.

Constructor Details

ViaRequest

public ViaRequest()

Constructs a new ViaRequest.

Method Details

process

public void process(HttpRequest request,
 EntityDetails entity,
 HttpContext context)
             throws ProtocolException,
IOException

Adds the HTTP HttpHeaders.VIA header to the request if it does not already exist.

This method ensures that the version of the request is HTTP/1.1 or higher, and adds the Via header in the format <protocol> <version> <host>, where <protocol> is the protocol name, <version> is the major and minor version of the request, and <host> is the value of the Host header.

In case the HttpHeaders.VIA header already exists, this method updates its value by appending the new protocol information in the same format.

If the version of the request is lower than HTTP/1.1 or the request authority not being specified, this method throws a ProtocolException.

Specified by:

process in interface HttpRequestInterceptor

Parameters:

request - the request object to modify

entity - the entity for the request, may be null

context - the context for the request

Throws:

ProtocolException - if there was a protocol error, such as the request version being lower than HTTP/1.1, or the request authority not being specified

IOException - if there was an I/O error