Remove engine.adapter and map Netty messages directly

changes.md

@@ -43,6 +43,13 @@ Changes log
           the connector for synchronous calls, without leaking credentials to other origins.
         - Removed `JettyServerHelper`, `JettyServerCall`, `JettyClientCall`, `JettyHandler`,
           `RestletSslContextFactoryClient` and `RestletSslContextFactoryServer`.
+        - Removed the `org.restlet.engine.adapter` package (`Adapter`, `Call`, `ClientAdapter`,
+          `ClientCall`, `HttpClientHelper`, `HttpRequest`, `HttpResponse`, `HttpServerHelper`,
+          `ServerAdapter`, `ServerCall`) and the "adapter" connector parameter. The Netty
+          connectors now map Netty messages directly to Restlet requests and responses, and
+          `NettyServerHelper` and `NettyClientHelper` extend `ServerHelper` and `ClientHelper`.
+          Custom HTTP connectors should extend those classes. Request headers remain available
+          with `Message.getHeaders()`.
         - `MultiPartRepresentation` no longer exposes Jetty types: parts are instances of the new
           `MultiPartRepresentation.Part` class (name, file name, headers, content
           representation), parsing takes an optional storage directory instead of a Jetty
@@ -54,6 +61,11 @@ Changes log
         - Removed the `Protocol.WAR` constant ("war" scheme, Web Archive Access Protocol), a
           leftover of the Servlet mode, which is no longer supported. `Protocol.valueOf("war")`
           now returns a new, unknown protocol. Use CLAP or FILE references instead.
+    - Enhancements
+        - Added `Response.getProtocol()` and `setProtocol()`: the protocol, with its version,
+          used by the server to reply (for example HTTP/1.1, HTTP/2.0 or HTTP/3.0), set by the HTTP
+          client connector. When unknown, the protocol of the request is returned.
+          `Response.toString()` now shows it.
     - Bugs fixed
         - Slf4j bridge reports wrong line number and caller class in log4j. Issue #233.
         - When GET is an allowed method of a server resource, HEAD is now also listed (e.g. in the Allow header of a 405 response). Issue #266.

org.restlet/src/main/java/module-info.java

@@ -33,7 +33,6 @@
     exports org.restlet;
     exports org.restlet.data;
     exports org.restlet.engine;
-    exports org.restlet.engine.adapter;
     exports org.restlet.engine.application;
     exports org.restlet.engine.component;
     exports org.restlet.engine.connector;

org.restlet/src/main/java/org/restlet/Response.java

@@ -19,6 +19,7 @@
 import org.restlet.data.CookieSetting;
 import org.restlet.data.Dimension;
 import org.restlet.data.Method;
+import org.restlet.data.Protocol;
 import org.restlet.data.Reference;
 import org.restlet.data.ServerInfo;
 import org.restlet.data.Status;
@@ -135,6 +136,9 @@ public static void setCurrent(Response response) {
     /** Indicates how long the service is expected to be unavailable to the requesting client. */
     private volatile Date retryAfter;
 
+    /** The protocol, with its version, used by the server to reply. */
+    private volatile Protocol protocol;
+
     /** The server-specific information. */
     private volatile ServerInfo serverInfo;
 
@@ -162,6 +166,7 @@ public Response(Request request) {
         this.locationRef = null;
         this.proxyChallengeRequests = null;
         this.request = request;
+        this.protocol = null;
         this.retryAfter = null;
         this.serverInfo = null;
         this.status = Status.SUCCESS_OK;
@@ -476,6 +481,18 @@ public Date getRetryAfter() {
         return retryAfter;
     }
 
+    /**
+     * Returns the protocol, with its version, used by the server to reply, if known. For example,
+     * the HTTP client connector sets "HTTP/1.1", "HTTP/2.0" or "HTTP/3.0" (secure exchanges use the
+     * HTTPS protocol). When unknown, returns the protocol of the request.
+     *
+     * @return The protocol used by the server to reply.
+     */
+    public Protocol getProtocol() {
+        Protocol result = this.protocol;
+        return (result == null && getRequest() != null) ? getRequest().getProtocol() : result;
+    }
+
     /**
      * Returns the server-specific information. Creates a new instance if no one has been set.
      *
@@ -932,6 +949,15 @@ public void setRetryAfter(Date retryAfter) {
         this.retryAfter = retryAfter;
     }
 
+    /**
+     * Sets the protocol, with its version, used by the server to reply.
+     *
+     * @param protocol The protocol used by the server to reply.
+     */
+    public void setProtocol(Protocol protocol) {
+        this.protocol = protocol;
+    }
+
     /**
      * Sets the server-specific information.
      *
@@ -987,6 +1013,7 @@ public void setStatus(Status status, Throwable throwable, String message) {
      * @return A synthesis of the response like an HTTP status line.
      */
     public String toString() {
-        return ((getRequest() == null) ? "?" : getRequest().getProtocol()) + " - " + getStatus();
+        Protocol p = getProtocol();
+        return ((p == null) ? "?" : p) + " - " + getStatus();
     }
 }