Introduce the notion of a default SessionProtocol

core/src/main/java/com/linecorp/armeria/client/AbstractWebClientBuilder.java

@@ -18,6 +18,8 @@
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.linecorp.armeria.common.SessionProtocol.httpAndHttpsValues;
 import static com.linecorp.armeria.internal.client.ClientUtil.UNDEFINED_URI;
+import static com.linecorp.armeria.internal.client.SessionProtocolUtil.defaultSessionProtocol;
+import static com.linecorp.armeria.internal.client.SessionProtocolUtil.maybeApplyDefaultProtocol;
 import static java.util.Objects.requireNonNull;
 
 import java.net.URI;
@@ -60,6 +62,13 @@ protected AbstractWebClientBuilder(URI uri) {
         this(validateUri(uri), null, null, null);
     }
 
+    /**
+     * Creates a new instance.
+     */
+    protected AbstractWebClientBuilder(EndpointGroup endpointGroup, @Nullable String path) {
+        this(defaultSessionProtocol(), requireNonNull(endpointGroup, "endpointGroup"), path);
+    }
+
     /**
      * Creates a new instance.
      *
@@ -87,6 +96,7 @@ protected AbstractWebClientBuilder(@Nullable URI uri, @Nullable Scheme scheme,
 
     private static URI validateUri(URI uri) {
         requireNonNull(uri, "uri");
+        uri = maybeApplyDefaultProtocol(uri);
         if (Clients.isUndefinedUri(uri)) {
             return uri;
         }

core/src/main/java/com/linecorp/armeria/client/ClientBuilder.java

@@ -16,6 +16,7 @@
 package com.linecorp.armeria.client;
 
 import static com.google.common.base.Preconditions.checkArgument;
+import static com.linecorp.armeria.internal.client.SessionProtocolUtil.maybeApplyDefaultProtocol;
 import static java.util.Objects.requireNonNull;
 
 import java.net.URI;
@@ -76,7 +77,7 @@ public final class ClientBuilder extends AbstractClientOptionsBuilder {
     private final Scheme scheme;
 
     ClientBuilder(URI uri) {
-        checkArgument(uri.getScheme() != null, "uri must have scheme: %s", uri);
+        uri = maybeApplyDefaultProtocol(uri);
         checkArgument(uri.getRawAuthority() != null, "uri must have authority: %s", uri);
         this.uri = uri;
         endpointGroup = null;

core/src/main/java/com/linecorp/armeria/client/Clients.java

@@ -16,6 +16,7 @@
 package com.linecorp.armeria.client;
 
 import static com.linecorp.armeria.internal.client.ClientUtil.UNDEFINED_URI;
+import static com.linecorp.armeria.internal.client.SessionProtocolUtil.defaultSessionProtocol;
 import static java.util.Objects.requireNonNull;
 
 import java.net.URI;
@@ -72,6 +73,17 @@ public static <T> T newClient(URI uri, Class<T> clientType) {
         return builder(uri).build(clientType);
     }
 
+    /**
+     * Creates a new client that connects to the specified {@link EndpointGroup} with
+     * the default {@link SessionProtocol} and {@link ClientFactory}.
+     *
+     * @param endpointGroup the server {@link EndpointGroup}
+     * @param clientType the type of the new client
+     */
+    public static <T> T newClient(EndpointGroup endpointGroup, Class<T> clientType) {
+        return builder(endpointGroup).build(clientType);
+    }
+
     /**
      * Creates a new client that connects to the specified {@link EndpointGroup} with the specified
      * {@code scheme} using the default {@link ClientFactory}.
@@ -88,6 +100,18 @@ public static <T> T newClient(String scheme, EndpointGroup endpointGroup, Class<
         return builder(scheme, endpointGroup).build(clientType);
     }
 
+    /**
+     * Creates a new client that connects to the specified {@link EndpointGroup} and
+     * {@code path} using the default {@link SessionProtocol} and {@link ClientFactory}.
+     *
+     * @param endpointGroup the server {@link EndpointGroup}
+     * @param path the path to the endpoint
+     * @param clientType the type of the new client
+     */
+    public static <T> T newClient(EndpointGroup endpointGroup, String path, Class<T> clientType) {
+        return builder(endpointGroup, path).build(clientType);
+    }
+
     /**
      * Creates a new client that connects to the specified {@link EndpointGroup} with the specified
      * {@code scheme} and {@code path} using the default {@link ClientFactory}.
@@ -192,6 +216,14 @@ public static ClientBuilder builder(URI uri) {
         return new ClientBuilder(requireNonNull(uri, "uri"));
     }
 
+    /**
+     * Returns a new {@link ClientBuilder} that builds the client that connects to the specified
+     * {@link EndpointGroup} using the default {@link SessionProtocol}.
+     */
+    public static ClientBuilder builder(EndpointGroup endpointGroup) {
+        return builder(Scheme.of(SerializationFormat.NONE, defaultSessionProtocol()), endpointGroup);
+    }
+
     /**
      * Returns a new {@link ClientBuilder} that builds the client that connects to the specified
      * {@link EndpointGroup} with the specified {@code scheme}.
@@ -202,6 +234,14 @@ public static ClientBuilder builder(String scheme, EndpointGroup endpointGroup)
         return builder(Scheme.parse(requireNonNull(scheme, "scheme")), endpointGroup);
     }
 
+    /**
+     * Returns a new {@link ClientBuilder} that builds the client that connects to the specified
+     * {@link EndpointGroup} and {@code path} using the default {@link SessionProtocol}.
+     */
+    public static ClientBuilder builder(EndpointGroup endpointGroup, String path) {
+        return builder(Scheme.of(SerializationFormat.NONE, defaultSessionProtocol()), endpointGroup, path);
+    }
+
     /**
      * Returns a new {@link ClientBuilder} that builds the client that connects to the specified
      * {@link EndpointGroup} with the specified {@code scheme} and {@code path}.

core/src/main/java/com/linecorp/armeria/client/DefaultWebClient.java

@@ -16,6 +16,7 @@
 
 package com.linecorp.armeria.client;
 
+import static com.linecorp.armeria.internal.client.SessionProtocolUtil.defaultSessionProtocol;
 import static java.util.Objects.requireNonNull;
 
 import com.google.common.base.Strings;
@@ -86,17 +87,16 @@ public HttpResponse execute(HttpRequest req, RequestOptions requestOptions) {
                 scheme = req.scheme();
                 authority = req.authority();
 
-                if (scheme == null || authority == null) {
+                if (authority == null) {
                     return abortRequestAndReturnFailureResponse(req, new IllegalArgumentException(
-                            "Scheme and authority must be specified in \":path\" or " +
-                            "in \":scheme\" and \":authority\". :path=" +
-                            originalPath + ", :scheme=" + req.scheme() + ", :authority=" + req.authority()));
+                            "Authority must be specified in \":path\" or " +
+                            "in \":authority\". :path=" + originalPath + ", :authority=" + req.authority()));
                 }
             }
 
             endpointGroup = Endpoint.parse(authority);
             try {
-                protocol = Scheme.parse(scheme).sessionProtocol();
+                protocol = computeSessionProtocol(scheme);
             } catch (Exception e) {
                 return abortRequestAndReturnFailureResponse(req, new IllegalArgumentException(
                         "Failed to parse a scheme: " + reqTarget.scheme(), e));
@@ -126,6 +126,13 @@ public HttpResponse execute(HttpRequest req, RequestOptions requestOptions) {
         return ClientUtil.executeWithFallback(preClient, ctx, newReq, errorResponseFactory());
     }
 
+    private static SessionProtocol computeSessionProtocol(@Nullable String scheme) {
+        if (scheme == null) {
+            return defaultSessionProtocol();
+        }
+        return Scheme.parse(scheme).sessionProtocol();
+    }
+
     private static HttpResponse abortRequestAndReturnFailureResponse(
             HttpRequest req, IllegalArgumentException cause) {
         req.abort(cause);

core/src/main/java/com/linecorp/armeria/client/RestClient.java

@@ -16,6 +16,7 @@
 
 package com.linecorp.armeria.client;
 
+import static com.linecorp.armeria.internal.client.SessionProtocolUtil.defaultSessionProtocol;
 import static java.util.Objects.requireNonNull;
 
 import java.net.URI;
@@ -78,6 +79,16 @@ static RestClient of(URI uri) {
         return builder(uri).build();
     }
 
+    /**
+     * Returns a new {@link RestClient} that connects to the specified {@link EndpointGroup} with
+     * the default {@link SessionProtocol}, {@link ClientFactory} and {@link ClientOptions}.
+     *
+     * @param endpointGroup the server {@link EndpointGroup}
+     */
+    static RestClient of(EndpointGroup endpointGroup) {
+        return builder(endpointGroup).build();
+    }
+
     /**
      * Returns a new {@link RestClient} that connects to the specified {@link EndpointGroup} with
      * the specified {@code protocol} using the default {@link ClientFactory} and the default
@@ -110,6 +121,18 @@ static RestClient of(SessionProtocol protocol, EndpointGroup endpointGroup) {
         return builder(protocol, endpointGroup).build();
     }
 
+    /**
+     * Returns a new {@link RestClient} that connects to the specified {@link EndpointGroup} and
+     * {@code path} using the default {@link SessionProtocol}, {@link ClientFactory} and
+     * the {@link ClientOptions}.
+     *
+     * @param endpointGroup the server {@link EndpointGroup}
+     * @param path the path to the endpoint
+     */
+    static RestClient of(EndpointGroup endpointGroup, String path) {
+        return builder(endpointGroup, path).build();
+    }
+
     /**
      * Returns a new {@link RestClient} that connects to the specified {@link EndpointGroup} with
      * the specified {@code protocol} and {@code path} using the default {@link ClientFactory} and
@@ -173,6 +196,15 @@ static RestClientBuilder builder(URI uri) {
         return new RestClientBuilder(uri);
     }
 
+    /**
+     * Returns a new {@link RestClientBuilder} created with the default {@link SessionProtocol}
+     * and base {@link EndpointGroup}.
+     */
+    static RestClientBuilder builder(EndpointGroup endpointGroup) {
+        requireNonNull(endpointGroup, "endpointGroup");
+        return builder(defaultSessionProtocol(), endpointGroup);
+    }
+
     /**
      * Returns a new {@link RestClientBuilder} created with the specified {@code protocol}
      * and base {@link EndpointGroup}.
@@ -199,6 +231,15 @@ static RestClientBuilder builder(SessionProtocol protocol, EndpointGroup endpoin
         return new RestClientBuilder(protocol, endpointGroup, null);
     }
 
+    /**
+     * Returns a new {@link RestClientBuilder} created with the base {@link EndpointGroup} and path.
+     */
+    static RestClientBuilder builder(EndpointGroup endpointGroup, String path) {
+        requireNonNull(endpointGroup, "endpointGroup");
+        requireNonNull(path, "path");
+        return builder(defaultSessionProtocol(), endpointGroup, path);
+    }
+
     /**
      * Returns a new {@link RestClientBuilder} created with the specified {@code protocol}.
      * base {@link EndpointGroup} and path.

core/src/main/java/com/linecorp/armeria/client/WebClient.java

@@ -79,6 +79,16 @@ static WebClient of(URI uri) {
         return builder(uri).build();
     }
 
+    /**
+     * Returns a new {@link WebClient} that connects to the specified {@link EndpointGroup}
+     * using the default {@link SessionProtocol}, {@link ClientFactory} and {@link ClientOptions}.
+     *
+     * @param endpointGroup the server {@link EndpointGroup}
+     */
+    static WebClient of(EndpointGroup endpointGroup) {
+        return builder(endpointGroup).build();
+    }
+
     /**
      * Returns a new {@link WebClient} that connects to the specified {@link EndpointGroup} with
      * the specified {@code protocol} using the default {@link ClientFactory} and the default
@@ -111,6 +121,18 @@ static WebClient of(SessionProtocol protocol, EndpointGroup endpointGroup) {
         return builder(protocol, endpointGroup).build();
     }
 
+    /**
+     * Returns a new {@link WebClient} that connects to the specified {@link EndpointGroup}
+     * and {@code path} using the default {@link SessionProtocol}, {@link ClientFactory} and
+     * {@link ClientOptions}.
+     *
+     * @param endpointGroup the server {@link EndpointGroup}
+     * @param path the path to the endpoint
+     */
+    static WebClient of(EndpointGroup endpointGroup, String path) {
+        return builder(endpointGroup, path).build();
+    }
+
     /**
      * Returns a new {@link WebClient} that connects to the specified {@link EndpointGroup} with
      * the specified {@code protocol} and {@code path} using the default {@link ClientFactory} and
@@ -174,6 +196,15 @@ static WebClientBuilder builder(URI uri) {
         return new WebClientBuilder(uri);
     }
 
+    /**
+     * Returns a new {@link WebClientBuilder} created with the default {@link SessionProtocol}
+     * and base {@link EndpointGroup}.
+     */
+    static WebClientBuilder builder(EndpointGroup endpointGroup) {
+        requireNonNull(endpointGroup, "endpointGroup");
+        return new WebClientBuilder(endpointGroup, null);
+    }
+
     /**
      * Returns a new {@link WebClientBuilder} created with the specified {@code protocol}
      * and base {@link EndpointGroup}.
@@ -200,6 +231,16 @@ static WebClientBuilder builder(SessionProtocol protocol, EndpointGroup endpoint
         return new WebClientBuilder(protocol, endpointGroup, null);
     }
 
+    /**
+     * Returns a new {@link WebClientBuilder} created with the default {@link SessionProtocol},
+     * base {@link EndpointGroup} and path.
+     */
+    static WebClientBuilder builder(EndpointGroup endpointGroup, String path) {
+        requireNonNull(endpointGroup, "endpointGroup");
+        requireNonNull(path, "path");
+        return new WebClientBuilder(endpointGroup, path);
+    }
+
     /**
      * Returns a new {@link WebClientBuilder} created with the specified {@code protocol}.
      * base {@link EndpointGroup} and path.

core/src/main/java/com/linecorp/armeria/client/WebClientBuilder.java

@@ -56,6 +56,13 @@ public final class WebClientBuilder extends AbstractWebClientBuilder {
         super(uri);
     }
 
+    /**
+     * Creates a new instance.
+     */
+    WebClientBuilder(EndpointGroup endpointGroup, @Nullable String path) {
+        super(endpointGroup, path);
+    }
+
     /**
      * Creates a new instance.
      *

core/src/main/java/com/linecorp/armeria/client/websocket/WebSocketClient.java

@@ -17,6 +17,7 @@
 package com.linecorp.armeria.client.websocket;
 
 import static com.linecorp.armeria.internal.client.ClientUtil.UNDEFINED_URI;
+import static com.linecorp.armeria.internal.client.SessionProtocolUtil.defaultSessionProtocol;
 import static java.util.Objects.requireNonNull;
 
 import java.net.URI;
@@ -97,6 +98,14 @@ static WebSocketClient of(URI uri) {
         return builder(uri).build();
     }
 
+    /**
+     * Returns a new {@link WebSocketClient} that connects to the specified {@link EndpointGroup} using
+     * the default {@link Scheme} and {@link ClientOptions}.
+     */
+    static WebSocketClient of(EndpointGroup endpointGroup) {
+        return builder(endpointGroup).build();
+    }
+
     /**
      * Returns a new {@link WebSocketClient} that connects to the specified {@link EndpointGroup} with
      * the specified {@code scheme} using the default {@link ClientOptions}.
@@ -121,6 +130,14 @@ static WebSocketClient of(SessionProtocol protocol, EndpointGroup endpointGroup)
         return builder(protocol, endpointGroup).build();
     }
 
+    /**
+     * Returns a new {@link WebSocketClient} that connects to the specified {@link EndpointGroup} with
+     * and {@code path} using the default {@link Scheme} and {@link ClientOptions}.
+     */
+    static WebSocketClient of(EndpointGroup endpointGroup, String path) {
+        return builder(endpointGroup, path).build();
+    }
+
     /**
      * Returns a new {@link WebSocketClient} that connects to the specified {@link EndpointGroup} with
      * the specified {@code scheme} and {@code path} using the default {@link ClientOptions}.
@@ -166,6 +183,14 @@ static WebSocketClientBuilder builder(URI uri) {
         return new WebSocketClientBuilder(requireNonNull(uri, "uri"));
     }
 
+    /**
+     * Returns a new {@link WebSocketClientBuilder} created with the specified {@link EndpointGroup}
+     * and the default {@link Scheme}.
+     */
+    static WebSocketClientBuilder builder(EndpointGroup endpointGroup) {
+        return builder(Scheme.of(SerializationFormat.WS, defaultSessionProtocol()), endpointGroup);
+    }
+
     /**
      * Returns a new {@link WebSocketClientBuilder} created with the specified {@code scheme}
      * and the {@link EndpointGroup}.
@@ -194,6 +219,14 @@ static WebSocketClientBuilder builder(SessionProtocol protocol, EndpointGroup en
         return builder(Scheme.of(SerializationFormat.WS, protocol), endpointGroup);
     }
 
+    /**
+     * Returns a new {@link WebSocketClientBuilder} created with the specified
+     * {@link EndpointGroup}, {@code path} and the default {@link Scheme}.
+     */
+    static WebSocketClientBuilder builder(EndpointGroup endpointGroup, String path) {
+        return builder(Scheme.of(SerializationFormat.WS, defaultSessionProtocol()), endpointGroup, path);
+    }
+
     /**
      * Returns a new {@link WebSocketClientBuilder} created with the specified {@code scheme},
      * the {@link EndpointGroup}, and the {@code path}.