Refactor RequestHandler to handle request component construction

This refactors RequestHandler so that it handles the construction of the request
component itself, rather than being handed a pre-built request component
instance constructed by the invoking servlet.

The motivation for this change is so that RequestHandler can be extended in
future CLs to compute authentication results, and can provide those results as
an available binding in the constructed request component.  An alternative
approach could have been to compute the authentication results within
RequestModule itself, but I think it's clearer to keep business logic like
that outside of Dagger providers.

This CL makes the following individual changes:

- Adds request component builders, which implement a RequestComponentBuilder
  interface so they can all be manipulated by RequestHandler

- Instead of obtaining request components via factory methods on the global
  components, one now can have global-scoped bindings just inject the request
  component builders (which requires adding a module to each global component
  declaring the subcomponent).  This follows the recommended approach here:
  http://google.github.io/dagger/subcomponents.html

- Instead of exposing request components on the global component interface,
  we now expose module-specific subclasses of RequestHandler that @Inject the
  appropriate request component builder's provider and pass it to the superclass
  (note that inheritance isn't strictly necessary here but saves boilerplate)

- RequestHandler now takes the Provider<RequestComponentBuilder> and builds
  the component itself using its own fresh RequestModule instance. This provides
  some nice encapsulation but is mainly needed for adding a RequestAuthModule
  in future work.

- RequestHandler also takes UserService now, which can be provided via Dagger
  by the subclass.  Longer-term that will go away in favor of instead providing
  AuthStrategy instances, some of which will use UserService internally.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=138815648

java/google/registry/module/backend/BUILD

@@ -13,6 +13,7 @@ java_library(
         "//java/com/google/common/base",
         "//java/com/google/common/collect",
         "//java/com/google/common/net",
+        "//third_party/java/appengine:appengine-api",
         "//third_party/java/bouncycastle",
         "//third_party/java/dagger",
         "//third_party/java/joda_time",

java/google/registry/module/backend/BackendComponent.java

@@ -26,6 +26,7 @@ import google.registry.groups.GroupsModule;
 import google.registry.groups.GroupssettingsModule;
 import google.registry.keyring.api.DummyKeyringModule;
 import google.registry.keyring.api.KeyModule;
+import google.registry.module.backend.BackendRequestComponent.BackendRequestComponentModule;
 import google.registry.monitoring.metrics.MetricReporter;
 import google.registry.monitoring.whitebox.StackdriverModule;
 import google.registry.rde.JSchModule;
@@ -37,7 +38,7 @@ import google.registry.request.Modules.ModulesServiceModule;
 import google.registry.request.Modules.URLFetchServiceModule;
 import google.registry.request.Modules.UrlFetchTransportModule;
 import google.registry.request.Modules.UseAppIdentityCredentialForGoogleApisModule;
-import google.registry.request.RequestModule;
+import google.registry.request.Modules.UserServiceModule;
 import google.registry.util.SystemClock.SystemClockModule;
 import google.registry.util.SystemSleeper.SystemSleeperModule;
 import javax.inject.Singleton;
@@ -47,6 +48,7 @@ import javax.inject.Singleton;
 @Component(
     modules = {
         AppIdentityCredentialModule.class,
+        BackendRequestComponentModule.class,
         BigqueryModule.class,
         ConfigModule.class,
         DatastoreServiceModule.class,
@@ -68,9 +70,10 @@ import javax.inject.Singleton;
         URLFetchServiceModule.class,
         UrlFetchTransportModule.class,
         UseAppIdentityCredentialForGoogleApisModule.class,
+        UserServiceModule.class,
         VoidDnsWriterModule.class,
     })
 interface BackendComponent {
-  BackendRequestComponent startRequest(RequestModule requestModule);
+  BackendRequestHandler requestHandler();
   MetricReporter metricReporter();
 }

java/google/registry/module/backend/BackendRequestComponent.java

@@ -14,6 +14,7 @@
 
 package google.registry.module.backend;
 
+import dagger.Module;
 import dagger.Subcomponent;
 import google.registry.backup.BackupModule;
 import google.registry.backup.CommitLogCheckpointAction;
@@ -56,6 +57,7 @@ import google.registry.rde.RdeReportAction;
 import google.registry.rde.RdeReporter;
 import google.registry.rde.RdeStagingAction;
 import google.registry.rde.RdeUploadAction;
+import google.registry.request.RequestComponentBuilder;
 import google.registry.request.RequestModule;
 import google.registry.request.RequestScope;
 import google.registry.tmch.NordnUploadAction;
@@ -120,4 +122,13 @@ interface BackendRequestComponent {
   TmchSmdrlAction tmchSmdrlAction();
   UpdateSnapshotViewAction updateSnapshotViewAction();
   VerifyEntityIntegrityAction verifyEntityIntegrityAction();
+
+  @Subcomponent.Builder
+  abstract class Builder implements RequestComponentBuilder<BackendRequestComponent, Builder> {
+    @Override public abstract Builder requestModule(RequestModule requestModule);
+    @Override public abstract BackendRequestComponent build();
+  }
+
+  @Module(subcomponents = BackendRequestComponent.class)
+  class BackendRequestComponentModule {}
 }

java/google/registry/module/backend/BackendRequestHandler.java

@@ -0,0 +1,31 @@
+// Copyright 2016 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.module.backend;
+
+import com.google.appengine.api.users.UserService;
+import google.registry.request.RequestHandler;
+import javax.inject.Inject;
+import javax.inject.Provider;
+
+/** Request handler for the backend module. */
+public class BackendRequestHandler
+    extends RequestHandler<BackendRequestComponent, BackendRequestComponent.Builder> {
+
+  @Inject BackendRequestHandler(
+      Provider<BackendRequestComponent.Builder> componentBuilderProvider,
+      UserService userService) {
+    super(componentBuilderProvider, userService);
+  }
+}

java/google/registry/module/backend/BackendServlet.java

@@ -15,8 +15,6 @@
 package google.registry.module.backend;
 
 import google.registry.monitoring.metrics.MetricReporter;
-import google.registry.request.RequestHandler;
-import google.registry.request.RequestModule;
 import google.registry.util.FormattingLogger;
 import java.io.IOException;
 import java.security.Security;
@@ -31,12 +29,10 @@ import org.bouncycastle.jce.provider.BouncyCastleProvider;
 public final class BackendServlet extends HttpServlet {
 
   private static final BackendComponent component = DaggerBackendComponent.create();
+  private static final BackendRequestHandler requestHandler = component.requestHandler();
   private static final MetricReporter metricReporter = component.metricReporter();
   private static final FormattingLogger logger = FormattingLogger.getLoggerForCallerClass();
 
-  private static final RequestHandler<BackendRequestComponent> requestHandler =
-      RequestHandler.create(BackendRequestComponent.class);
-
   @Override
   public void init() {
     Security.addProvider(new BouncyCastleProvider());
@@ -61,6 +57,6 @@ public final class BackendServlet extends HttpServlet {
 
   @Override
   public void service(HttpServletRequest req, HttpServletResponse rsp) throws IOException {
-    requestHandler.handleRequest(req, rsp, component.startRequest(new RequestModule(req, rsp)));
+    requestHandler.handleRequest(req, rsp);
   }
 }

java/google/registry/module/frontend/BUILD

@@ -11,6 +11,7 @@ java_library(
     deps = [
         "//java/com/google/common/base",
         "//java/com/google/common/collect",
+        "//third_party/java/appengine:appengine-api",
         "//third_party/java/bouncycastle",
         "//third_party/java/dagger",
         "//third_party/java/jsr305_annotations",

java/google/registry/module/frontend/FrontendComponent.java

@@ -19,6 +19,7 @@ import google.registry.braintree.BraintreeModule;
 import google.registry.config.ConfigModule;
 import google.registry.keyring.api.DummyKeyringModule;
 import google.registry.keyring.api.KeyModule;
+import google.registry.module.frontend.FrontendRequestComponent.FrontendRequestComponentModule;
 import google.registry.monitoring.metrics.MetricReporter;
 import google.registry.monitoring.whitebox.StackdriverModule;
 import google.registry.request.Modules.AppIdentityCredentialModule;
@@ -27,7 +28,6 @@ import google.registry.request.Modules.ModulesServiceModule;
 import google.registry.request.Modules.UrlFetchTransportModule;
 import google.registry.request.Modules.UseAppIdentityCredentialForGoogleApisModule;
 import google.registry.request.Modules.UserServiceModule;
-import google.registry.request.RequestModule;
 import google.registry.ui.ConsoleConfigModule;
 import google.registry.util.SystemClock.SystemClockModule;
 import javax.inject.Singleton;
@@ -42,6 +42,7 @@ import javax.inject.Singleton;
         ConsoleConfigModule.class,
         DummyKeyringModule.class,
         FrontendMetricsModule.class,
+        FrontendRequestComponentModule.class,
         Jackson2Module.class,
         KeyModule.class,
         ModulesServiceModule.class,
@@ -52,6 +53,6 @@ import javax.inject.Singleton;
         UserServiceModule.class,
     })
 interface FrontendComponent {
-  FrontendRequestComponent startRequest(RequestModule requestModule);
+  FrontendRequestHandler requestHandler();
   MetricReporter metricReporter();
 }

java/google/registry/module/frontend/FrontendRequestComponent.java

@@ -14,6 +14,7 @@
 
 package google.registry.module.frontend;
 
+import dagger.Module;
 import dagger.Subcomponent;
 import google.registry.dns.DnsModule;
 import google.registry.flows.CheckApiAction;
@@ -33,6 +34,7 @@ import google.registry.rdap.RdapIpAction;
 import google.registry.rdap.RdapModule;
 import google.registry.rdap.RdapNameserverAction;
 import google.registry.rdap.RdapNameserverSearchAction;
+import google.registry.request.RequestComponentBuilder;
 import google.registry.request.RequestModule;
 import google.registry.request.RequestScope;
 import google.registry.ui.server.registrar.ConsoleUiAction;
@@ -77,4 +79,13 @@ interface FrontendRequestComponent {
   RdapNameserverSearchAction rdapNameserverSearchAction();
   WhoisHttpServer whoisHttpServer();
   WhoisServer whoisServer();
+
+  @Subcomponent.Builder
+  abstract class Builder implements RequestComponentBuilder<FrontendRequestComponent, Builder> {
+    @Override public abstract Builder requestModule(RequestModule requestModule);
+    @Override public abstract FrontendRequestComponent build();
+  }
+
+  @Module(subcomponents = FrontendRequestComponent.class)
+  class FrontendRequestComponentModule {}
 }

java/google/registry/module/frontend/FrontendRequestHandler.java

@@ -0,0 +1,31 @@
+// Copyright 2016 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.module.frontend;
+
+import com.google.appengine.api.users.UserService;
+import google.registry.request.RequestHandler;
+import javax.inject.Inject;
+import javax.inject.Provider;
+
+/** Request handler for the frontend module. */
+public class FrontendRequestHandler
+    extends RequestHandler<FrontendRequestComponent, FrontendRequestComponent.Builder> {
+
+  @Inject FrontendRequestHandler(
+      Provider<FrontendRequestComponent.Builder> componentBuilderProvider,
+      UserService userService) {
+    super(componentBuilderProvider, userService);
+  }
+}

java/google/registry/module/frontend/FrontendServlet.java

@@ -15,8 +15,6 @@
 package google.registry.module.frontend;
 
 import google.registry.monitoring.metrics.MetricReporter;
-import google.registry.request.RequestHandler;
-import google.registry.request.RequestModule;
 import google.registry.util.FormattingLogger;
 import java.io.IOException;
 import java.security.Security;
@@ -31,12 +29,10 @@ import org.bouncycastle.jce.provider.BouncyCastleProvider;
 public final class FrontendServlet extends HttpServlet {
 
   private static final FrontendComponent component = DaggerFrontendComponent.create();
+  private static final FrontendRequestHandler requestHandler = component.requestHandler();
   private static final MetricReporter metricReporter = component.metricReporter();
   private static final FormattingLogger logger = FormattingLogger.getLoggerForCallerClass();
 
-  private static final RequestHandler<FrontendRequestComponent> requestHandler =
-      RequestHandler.create(FrontendRequestComponent.class);
-
   @Override
   public void init() {
     Security.addProvider(new BouncyCastleProvider());
@@ -61,6 +57,6 @@ public final class FrontendServlet extends HttpServlet {
 
   @Override
   public void service(HttpServletRequest req, HttpServletResponse rsp) throws IOException {
-    requestHandler.handleRequest(req, rsp, component.startRequest(new RequestModule(req, rsp)));
+    requestHandler.handleRequest(req, rsp);
   }
 }

java/google/registry/module/tools/BUILD

@@ -11,6 +11,7 @@ java_library(
     deps = [
         "//java/com/google/common/base",
         "//java/com/google/common/collect",
+        "//third_party/java/appengine:appengine-api",
         "//third_party/java/bouncycastle",
         "//third_party/java/dagger",
         "//third_party/java/jsr305_annotations",

java/google/registry/module/tools/ToolsComponent.java

@@ -23,6 +23,7 @@ import google.registry.groups.GroupsModule;
 import google.registry.groups.GroupssettingsModule;
 import google.registry.keyring.api.DummyKeyringModule;
 import google.registry.keyring.api.KeyModule;
+import google.registry.module.tools.ToolsRequestComponent.ToolsRequestComponentModule;
 import google.registry.request.Modules.AppIdentityCredentialModule;
 import google.registry.request.Modules.DatastoreServiceModule;
 import google.registry.request.Modules.GoogleCredentialModule;
@@ -30,7 +31,7 @@ import google.registry.request.Modules.Jackson2Module;
 import google.registry.request.Modules.ModulesServiceModule;
 import google.registry.request.Modules.UrlFetchTransportModule;
 import google.registry.request.Modules.UseAppIdentityCredentialForGoogleApisModule;
-import google.registry.request.RequestModule;
+import google.registry.request.Modules.UserServiceModule;
 import google.registry.util.SystemClock.SystemClockModule;
 import google.registry.util.SystemSleeper.SystemSleeperModule;
 import javax.inject.Singleton;
@@ -52,11 +53,13 @@ import javax.inject.Singleton;
         Jackson2Module.class,
         KeyModule.class,
         ModulesServiceModule.class,
+        ToolsRequestComponentModule.class,
         UrlFetchTransportModule.class,
         UseAppIdentityCredentialForGoogleApisModule.class,
+        UserServiceModule.class,
         SystemClockModule.class,
         SystemSleeperModule.class,
     })
 interface ToolsComponent {
-  ToolsRequestComponent startRequest(RequestModule requestModule);
+  ToolsRequestHandler requestHandler();
 }

java/google/registry/module/tools/ToolsRequestComponent.java

@@ -14,6 +14,7 @@
 
 package google.registry.module.tools;
 
+import dagger.Module;
 import dagger.Subcomponent;
 import google.registry.dns.DnsModule;
 import google.registry.export.PublishDetailReportAction;
@@ -24,6 +25,7 @@ import google.registry.loadtest.LoadTestAction;
 import google.registry.loadtest.LoadTestModule;
 import google.registry.mapreduce.MapreduceModule;
 import google.registry.monitoring.whitebox.WhiteboxModule;
+import google.registry.request.RequestComponentBuilder;
 import google.registry.request.RequestModule;
 import google.registry.request.RequestScope;
 import google.registry.tools.server.CreateGroupsAction;
@@ -77,4 +79,13 @@ interface ToolsRequestComponent {
   ResaveAllEppResourcesAction resaveAllEppResourcesAction();
   UpdatePremiumListAction updatePremiumListAction();
   VerifyOteAction verifyOteAction();
+
+  @Subcomponent.Builder
+  abstract class Builder implements RequestComponentBuilder<ToolsRequestComponent, Builder> {
+    @Override public abstract Builder requestModule(RequestModule requestModule);
+    @Override public abstract ToolsRequestComponent build();
+  }
+
+  @Module(subcomponents = ToolsRequestComponent.class)
+  class ToolsRequestComponentModule {}
 }

java/google/registry/module/tools/ToolsRequestHandler.java

@@ -0,0 +1,31 @@
+// Copyright 2016 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.module.tools;
+
+import com.google.appengine.api.users.UserService;
+import google.registry.request.RequestHandler;
+import javax.inject.Inject;
+import javax.inject.Provider;
+
+/** Request handler for the tools module. */
+public class ToolsRequestHandler
+    extends RequestHandler<ToolsRequestComponent, ToolsRequestComponent.Builder> {
+
+  @Inject ToolsRequestHandler(
+      Provider<ToolsRequestComponent.Builder> componentBuilderProvider,
+      UserService userService) {
+    super(componentBuilderProvider, userService);
+  }
+}

java/google/registry/module/tools/ToolsServlet.java

@@ -14,8 +14,6 @@
 
 package google.registry.module.tools;
 
-import google.registry.request.RequestHandler;
-import google.registry.request.RequestModule;
 import java.io.IOException;
 import java.security.Security;
 import javax.servlet.http.HttpServlet;
@@ -27,9 +25,7 @@ import org.bouncycastle.jce.provider.BouncyCastleProvider;
 public final class ToolsServlet extends HttpServlet {
 
   private static final ToolsComponent component = DaggerToolsComponent.create();
-
-  private static final RequestHandler<ToolsRequestComponent> requestHandler =
-      RequestHandler.create(ToolsRequestComponent.class);
+  private static final ToolsRequestHandler requestHandler = component.requestHandler();
 
   @Override
   public void init() {
@@ -38,6 +34,6 @@ public final class ToolsServlet extends HttpServlet {
 
   @Override
   public void service(HttpServletRequest req, HttpServletResponse rsp) throws IOException {
-    requestHandler.handleRequest(req, rsp, component.startRequest(new RequestModule(req, rsp)));
+    requestHandler.handleRequest(req, rsp);
   }
 }

java/google/registry/request/RequestComponentBuilder.java

@@ -0,0 +1,25 @@
+// Copyright 2016 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.request;
+
+/**
+ * Builder interface for request components.
+ *
+ * @see RequestHandler
+ */
+public interface RequestComponentBuilder<C, B extends RequestComponentBuilder<C, B>> {
+  B requestModule(RequestModule requestModule);
+  C build();
+}

java/google/registry/request/RequestHandler.java

@@ -26,17 +26,18 @@ import static javax.servlet.http.HttpServletResponse.SC_MOVED_TEMPORARILY;
 import static javax.servlet.http.HttpServletResponse.SC_NOT_FOUND;
 
 import com.google.appengine.api.users.UserService;
-import com.google.appengine.api.users.UserServiceFactory;
 import com.google.common.base.Optional;
 import google.registry.util.FormattingLogger;
-import google.registry.util.NonFinalForTesting;
+import google.registry.util.TypeUtils.TypeInstantiator;
 import java.io.IOException;
+import javax.annotation.Nullable;
+import javax.inject.Provider;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import org.joda.time.Duration;
 
 /**
- * Dagger request processor for Nomulus.
+ * Dagger-based request processor.
  *
  * <p>This class creates an HTTP request processor from a Dagger component. It routes requests from
  * your servlet to an {@link Action @Action} annotated handler class.
@@ -64,37 +65,58 @@ import org.joda.time.Duration;
  *
  * <p>This class also enforces the {@link Action#requireLogin() requireLogin} setting.
  *
- * @param <C> component type
+ * @param <C> request component type
+ * @param <B> builder for the request component
  */
-public final class RequestHandler<C> {
+public class RequestHandler<C, B extends RequestComponentBuilder<C, B>> {
 
   private static final FormattingLogger logger = FormattingLogger.getLoggerForCallerClass();
 
   private static final Duration XSRF_VALIDITY = Duration.standardDays(1);
 
-  @NonFinalForTesting
-  private static UserService userService = UserServiceFactory.getUserService();
-
-  /** Creates a new request processor based off your component methods. */
-  public static <C> RequestHandler<C> create(Class<C> component) {
-    return new RequestHandler<>(component, Router.create(component));
-  }
-
   private final Router router;
-
-  private RequestHandler(Class<C> component, Router router) {
-    checkNotNull(component);
-    this.router = router;
-  }
+  private final Provider<B> requestComponentBuilderProvider;
+  private final UserService userService;
 
   /**
-   * Runs the appropriate action for a servlet request.
+   * Constructor for subclasses to create a new request handler for a specific request component.
    *
-   * @param component is an instance of the component type passed to {@link #create(Class)}
+   * <p>This operation will generate a routing map for the component's {@code @Action}-returning
+   * methods using reflection, which is moderately expensive, so a given servlet should construct a
+   * single {@code RequestHandler} and re-use it across requests.
+   *
+   * @param requestComponentBuilderProvider a Dagger {@code Provider} of builder instances that can
+   *     be used to construct new instances of the request component (with the required
+   *     request-derived modules provided by this class)
+   * @param userService an instance of the App Engine UserService API
    */
-  public void handleRequest(HttpServletRequest req, HttpServletResponse rsp, C component)
-      throws IOException {
-    checkNotNull(component);
+  protected RequestHandler(Provider<B> requestComponentBuilderProvider, UserService userService) {
+    this(null, requestComponentBuilderProvider, userService);
+  }
+
+  /** Creates a new RequestHandler with an explicit component class for test purposes. */
+  public static <C, B extends RequestComponentBuilder<C, B>> RequestHandler<C, B> createForTest(
+      Class<C> component, Provider<B> requestComponentBuilderProvider, UserService userService) {
+    return new RequestHandler<>(
+        checkNotNull(component), requestComponentBuilderProvider, userService);
+  }
+
+  private RequestHandler(
+      @Nullable Class<C> component,
+      Provider<B> requestComponentBuilderProvider,
+      UserService userService) {
+    // If the component class isn't explicitly provided, infer it from the class's own typing.
+    // This is safe only for use by subclasses of RequestHandler where the generic parameter is
+    // preserved at runtime, so only expose that option via the protected constructor.
+    this.router = Router.create(
+        component != null ? component : new TypeInstantiator<C>(getClass()){}.getExactType());
+    this.requestComponentBuilderProvider = checkNotNull(requestComponentBuilderProvider);
+    this.userService = checkNotNull(userService);
+  }
+
+  /** Runs the appropriate action for a servlet request. */
+  public void handleRequest(HttpServletRequest req, HttpServletResponse rsp) throws IOException {
+    checkNotNull(req);
     checkNotNull(rsp);
     Action.Method method;
     try {
@@ -130,6 +152,11 @@ public final class RequestHandler<C> {
       rsp.sendError(SC_FORBIDDEN, "Invalid " + X_CSRF_TOKEN);
       return;
     }
+    // Build a new request component using any modules we've constructed by this point.
+    C component = requestComponentBuilderProvider.get()
+        .requestModule(new RequestModule(req, rsp))
+        .build();
+    // Apply the selected Route to the component to produce an Action instance, and run it.
     try {
       route.get().instantiator().apply(component).run();
       if (route.get().action().automaticallyPrintOk()) {

javatests/google/registry/request/RequestHandlerTest.java

@@ -28,6 +28,7 @@ import com.google.common.testing.NullPointerTester;
 import google.registry.request.HttpException.ServiceUnavailableException;
 import google.registry.testing.AppEngineRule;
 import google.registry.testing.InjectRule;
+import google.registry.testing.Providers;
 import google.registry.testing.UserInfo;
 import java.io.PrintWriter;
 import java.io.StringWriter;
@@ -125,6 +126,14 @@ public final class RequestHandlerTest {
     }
   }
 
+  /** Fake Builder for the fake component above to satisfy RequestHandler expectations. */
+  public abstract static class Builder implements RequestComponentBuilder<Component, Builder> {
+    @Override
+    public Builder requestModule(RequestModule requestModule) {
+      return this;
+    }
+  }
+
   @Mock
   private HttpServletRequest req;
 
@@ -148,11 +157,21 @@ public final class RequestHandlerTest {
 
   private final Component component = new Component();
   private final StringWriter httpOutput = new StringWriter();
-  private final RequestHandler<Component> handler = RequestHandler.create(Component.class);
+  private RequestHandler<Component, Builder> handler;
 
   @Before
   public void before() throws Exception {
-    inject.setStaticField(RequestHandler.class, "userService", userService);
+    // Initialize here, not inline, so that we pick up the mocked UserService.
+    handler = RequestHandler.createForTest(
+        Component.class,
+        Providers.of(new Builder() {
+          @Override
+          public Component build() {
+            // Use a fake Builder that returns the single component instance that uses the mocks.
+            return component;
+          }
+        }),
+        userService);
     when(rsp.getWriter()).thenReturn(new PrintWriter(httpOutput));
   }
 
@@ -165,7 +184,7 @@ public final class RequestHandlerTest {
   public void testHandleRequest_normalRequest_works() throws Exception {
     when(req.getMethod()).thenReturn("GET");
     when(req.getRequestURI()).thenReturn("/bumblebee");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verifyZeroInteractions(rsp);
     verify(bumblebeeTask).run();
   }
@@ -174,7 +193,7 @@ public final class RequestHandlerTest {
   public void testHandleRequest_multipleMethodMappings_works() throws Exception {
     when(req.getMethod()).thenReturn("POST");
     when(req.getRequestURI()).thenReturn("/bumblebee");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(bumblebeeTask).run();
   }
 
@@ -182,7 +201,7 @@ public final class RequestHandlerTest {
   public void testHandleRequest_prefixEnabled_subpathsWork() throws Exception {
     when(req.getMethod()).thenReturn("GET");
     when(req.getRequestURI()).thenReturn("/bumblebee/hive");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(bumblebeeTask).run();
   }
 
@@ -190,7 +209,7 @@ public final class RequestHandlerTest {
   public void testHandleRequest_taskHasAutoPrintOk_printsOk() throws Exception {
     when(req.getMethod()).thenReturn("POST");
     when(req.getRequestURI()).thenReturn("/sloth");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(slothTask).run();
     verify(rsp).setContentType("text/plain; charset=utf-8");
     verify(rsp).getWriter();
@@ -201,7 +220,7 @@ public final class RequestHandlerTest {
   public void testHandleRequest_prefixDisabled_subpathsReturn404NotFound() throws Exception {
     when(req.getMethod()).thenReturn("POST");
     when(req.getRequestURI()).thenReturn("/sloth/nest");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(rsp).sendError(404);
   }
 
@@ -209,7 +228,7 @@ public final class RequestHandlerTest {
   public void testHandleRequest_taskThrowsHttpException_getsHandledByHandler() throws Exception {
     when(req.getMethod()).thenReturn("GET");
     when(req.getRequestURI()).thenReturn("/fail");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(rsp).sendError(503, "Set sail for fail");
   }
 
@@ -219,7 +238,7 @@ public final class RequestHandlerTest {
       throws Exception {
     when(req.getMethod()).thenReturn("GET");
     when(req.getRequestURI()).thenReturn("/failAtConstruction");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(rsp).sendError(503, "Fail at construction");
   }
 
@@ -227,7 +246,7 @@ public final class RequestHandlerTest {
   public void testHandleRequest_notFound_returns404NotFound() throws Exception {
     when(req.getMethod()).thenReturn("GET");
     when(req.getRequestURI()).thenReturn("/bogus");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(rsp).sendError(404);
   }
 
@@ -235,7 +254,7 @@ public final class RequestHandlerTest {
   public void testHandleRequest_methodNotAllowed_returns405MethodNotAllowed() throws Exception {
     when(req.getMethod()).thenReturn("POST");
     when(req.getRequestURI()).thenReturn("/fail");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(rsp).sendError(405);
   }
 
@@ -243,7 +262,7 @@ public final class RequestHandlerTest {
   public void testHandleRequest_insaneMethod_returns405MethodNotAllowed() throws Exception {
     when(req.getMethod()).thenReturn("FIREAWAY");
     when(req.getRequestURI()).thenReturn("/fail");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(rsp).sendError(405);
   }
 
@@ -253,7 +272,7 @@ public final class RequestHandlerTest {
   public void testHandleRequest_lowercaseMethod_notRecognized() throws Exception {
     when(req.getMethod()).thenReturn("get");
     when(req.getRequestURI()).thenReturn("/bumblebee");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(rsp).sendError(405);
   }
 
@@ -268,7 +287,7 @@ public final class RequestHandlerTest {
   public void testXsrfProtection_noTokenProvided_returns403Forbidden() throws Exception {
     when(req.getMethod()).thenReturn("POST");
     when(req.getRequestURI()).thenReturn("/safe-sloth");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(rsp).sendError(403, "Invalid X-CSRF-Token");
   }
 
@@ -277,7 +296,7 @@ public final class RequestHandlerTest {
     when(req.getMethod()).thenReturn("POST");
     when(req.getHeader("X-CSRF-Token")).thenReturn(generateToken("vampire"));
     when(req.getRequestURI()).thenReturn("/safe-sloth");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(safeSlothTask).run();
   }
 
@@ -286,7 +305,7 @@ public final class RequestHandlerTest {
     when(req.getMethod()).thenReturn("POST");
     when(req.getHeader("X-CSRF-Token")).thenReturn(generateToken("blood"));
     when(req.getRequestURI()).thenReturn("/safe-sloth");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(rsp).sendError(403, "Invalid X-CSRF-Token");
   }
 
@@ -294,7 +313,7 @@ public final class RequestHandlerTest {
   public void testXsrfProtection_GETMethodWithoutToken_doesntCheckToken() throws Exception {
     when(req.getMethod()).thenReturn("GET");
     when(req.getRequestURI()).thenReturn("/safe-sloth");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(safeSlothTask).run();
   }
 
@@ -304,7 +323,7 @@ public final class RequestHandlerTest {
     when(userService.createLoginURL("/users-only")).thenReturn("/login");
     when(req.getMethod()).thenReturn("GET");
     when(req.getRequestURI()).thenReturn("/users-only");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(rsp).setStatus(302);
     verify(rsp).setHeader("Location", "/login");
   }
@@ -314,7 +333,7 @@ public final class RequestHandlerTest {
     when(userService.isUserLoggedIn()).thenReturn(true);
     when(req.getMethod()).thenReturn("GET");
     when(req.getRequestURI()).thenReturn("/users-only");
-    handler.handleRequest(req, rsp, component);
+    handler.handleRequest(req, rsp);
     verify(usersOnlyAction).run();
   }
 }