Migrated attachment for Guice issue 49, comment 20

GUICE_ISSUE_49_PATCH_SUGGESTION_20071107.txt

Index: src/com/google/inject/Binder.java
===================================================================
--- src/com/google/inject/Binder.java	(revision 379)
+++ src/com/google/inject/Binder.java	(working copy)
@@ -20,6 +20,7 @@
 import com.google.inject.binder.AnnotatedConstantBindingBuilder;
 import com.google.inject.binder.LinkedBindingBuilder;
 import com.google.inject.matcher.Matcher;
+import com.google.inject.spi.Dependency;
 import com.google.inject.spi.Message;
 import com.google.inject.spi.TypeConverter;
 import java.lang.annotation.Annotation;
@@ -225,6 +226,16 @@
   AnnotatedConstantBindingBuilder bindConstant();
 
   /**
+   * Binds a binding factory to missing dependencies matched by a matcher.
+   *
+   * @param dependencyMatcher matches missing dependencies the binding factory
+   *     should attempt to satisfy. For example: {@code any()}.
+   * @param bindingFactory factory that can produce bindings on request
+   */
+  void bind(Matcher<? super Dependency<?>> dependencyMatcher,
+      BindingFactory<?> bindingFactory);
+
+  /**
    * Upon successful creation, the {@link Injector} will inject static fields
    * and methods in the given classes.
    *
Index: src/com/google/inject/InjectorImpl.java
===================================================================
--- src/com/google/inject/InjectorImpl.java	(revision 379)
+++ src/com/google/inject/InjectorImpl.java	(working copy)
@@ -93,6 +93,8 @@
 
   ErrorHandler errorHandler = new InvalidErrorHandler();
 
+  MissingDependencyHandler missingDependencyHandler;
+
   InjectorImpl(ConstructionProxyFactory constructionProxyFactory,
       Map<Key<?>, BindingImpl<?>> bindings,
       Map<Class<? extends Annotation>, Scope> scopes,
@@ -147,6 +149,10 @@
     this.errorHandler = errorHandler;
   }
 
+  void setMissingDependencyHandler(MissingDependencyHandler dependencyHandler) {
+    this.missingDependencyHandler = dependencyHandler;
+  }
+
   /**
    * Gets a binding implementation. First, this checks for an explicit binding.
    * If no explicit binding is found, it looks for a just-in-time binding.
@@ -799,20 +805,34 @@
 
       final Key<?> key = Key.get(
           field.getGenericType(), field, field.getAnnotations(), errorHandler);
-      factory = SourceProviders.withDefault(StackTraceElements.forMember(field),
-        new Callable<InternalFactory<?>>() {
-          public InternalFactory<?> call() throws Exception {
-            return injector.getInternalFactory(key);
-          }
+
+      this.injectionPoint = InjectionPoint.newInstance(field,
+          Nullability.forAnnotations(field.getAnnotations()), key, injector);
+
+      // try this at most twice
+      InternalFactory<?> factory = null;
+      for (int i = 0; i < 2; i++) {
+        factory = SourceProviders.withDefault(
+            StackTraceElements.forMember(field),
+            new Callable<InternalFactory<?>>() {
+              public InternalFactory<?> call() throws Exception {
+                return injector.getInternalFactory(key);
+              }
+            }
+        );
+
+        // bail out early if nothing has changed
+        if (factory != null || missingDependencyHandler == null
+            || !missingDependencyHandler.handle(this.injectionPoint)) {
+          break;
         }
-      );
+      }
 
       if (factory == null) {
         throw new MissingDependencyException(key, field);
       }
 
-      this.injectionPoint = InjectionPoint.newInstance(field,
-          Nullability.forAnnotations(field.getAnnotations()), key, injector);
+      this.factory = factory;
     }
 
     public Collection<Dependency<?>> getDependencies() {
@@ -876,21 +896,33 @@
   <T> SingleParameterInjector<T> createParameterInjector(
       final Key<T> key, Member member, int index, Annotation[] annotations)
       throws MissingDependencyException {
-    InternalFactory<? extends T> factory =
-        SourceProviders.withDefault(StackTraceElements.forMember(member),
-      new Callable<InternalFactory<? extends T>>() {
-        public InternalFactory<? extends T> call() throws Exception {
-          return getInternalFactory(key);
-        }
+
+    InjectionPoint<T> injectionPoint = InjectionPoint.newInstance(
+        member, index, Nullability.forAnnotations(annotations), key, this);
+
+    // try this at most twice
+    InternalFactory<? extends T> factory = null;
+    for (int i = 0; i < 2; i++) {
+      factory = SourceProviders.withDefault(
+          StackTraceElements.forMember(member),
+          new Callable<InternalFactory<? extends T>>() {
+            public InternalFactory<? extends T> call() throws Exception {
+              return getInternalFactory(key);
+            }
+          }
+      );
+
+      // bail out early if nothing has changed
+      if (factory != null || missingDependencyHandler == null
+          || !missingDependencyHandler.handle(injectionPoint)) {
+        break;
       }
-    );
+    }
 
     if (factory == null) {
       throw new MissingDependencyException(key, member);
     }
 
-    InjectionPoint<T> injectionPoint = InjectionPoint.newInstance(
-        member, index, Nullability.forAnnotations(annotations), key, this);
     return new SingleParameterInjector<T>(injectionPoint, factory);
   }
 
Index: src/com/google/inject/BindingFactory.java
===================================================================
--- src/com/google/inject/BindingFactory.java	(revision 0)
+++ src/com/google/inject/BindingFactory.java	(revision 0)
@@ -0,0 +1,41 @@
+/**
+ * Copyright (C) 2007 Google Inc.
+ *
+ * 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 com.google.inject;
+
+import com.google.inject.binder.LinkedBindingBuilder;
+import com.google.inject.spi.Dependency;
+
+/**
+ * A factory capable of supplying bindings on request during construction of
+ * the {@code Injector}. Binding factories can be used to integrate service
+ * registries with Guice.
+ *
+ * @author stuart.mcculloch@jayway.net (Stuart McCulloch)
+ */
+public interface BindingFactory<B> {
+
+  /**
+   * Supplies bindings for missing dependencies that extend {@code B}
+   * 
+   * @param <T> a type of dependency this factory can supply
+   * @param dependency the missing dependency that needs a binding
+   * @param linkedBindingBuilder a partially constructed binding
+   * @return true if this factory could supply a binding
+   */
+  <T extends B> boolean bind(Dependency<T> dependency,
+      LinkedBindingBuilder<T> linkedBindingBuilder);
+}

Property changes on: src/com/google/inject/BindingFactory.java
___________________________________________________________________
Name: svn:eol-style
   + native

Index: src/com/google/inject/MissingDependencyHandler.java
===================================================================
--- src/com/google/inject/MissingDependencyHandler.java	(revision 0)
+++ src/com/google/inject/MissingDependencyHandler.java	(revision 0)
@@ -0,0 +1,32 @@
+/**
+ * Copyright (C) 2007 Google Inc.
+ *
+ * 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 com.google.inject;
+
+import com.google.inject.spi.Dependency;
+
+/**
+ * Handles missing dependencies in the Injector.
+ *
+ * @author stuart.mcculloch@jayway.net (Stuart McCulloch)
+ */
+interface MissingDependencyHandler {
+
+  /**
+   * Handles a missing dependency.
+   */
+  boolean handle(Dependency<?> dependency);
+}

Property changes on: src/com/google/inject/MissingDependencyHandler.java
___________________________________________________________________
Name: svn:eol-style
   + native

Index: src/com/google/inject/AbstractModule.java
===================================================================
--- src/com/google/inject/AbstractModule.java	(revision 379)
+++ src/com/google/inject/AbstractModule.java	(working copy)
@@ -21,6 +21,7 @@
 import com.google.inject.binder.LinkedBindingBuilder;
 import com.google.inject.internal.Objects;
 import com.google.inject.matcher.Matcher;
+import com.google.inject.spi.Dependency;
 import com.google.inject.spi.SourceProviders;
 import com.google.inject.spi.TypeConverter;
 import java.lang.annotation.Annotation;
@@ -120,6 +121,15 @@
   }
 
   /**
+   * @see Binder#bind(Matcher, BindingFactory)
+   */
+  protected void bind(Matcher<? super Dependency<?>> dependencyMatcher,
+      BindingFactory<?> bindingFactory)
+  {
+    binder.bind(dependencyMatcher, bindingFactory);
+  }
+
+  /**
    * @see Binder#install(Module)
    */
   protected void install(Module module) {
Index: src/com/google/inject/BinderImpl.java
===================================================================
--- src/com/google/inject/BinderImpl.java	(revision 379)
+++ src/com/google/inject/BinderImpl.java	(working copy)
@@ -18,6 +18,7 @@
 
 import com.google.inject.InjectorImpl.SingleMemberInjector;
 import static com.google.inject.Scopes.SINGLETON;
+import com.google.inject.binder.LinkedBindingBuilder;
 import com.google.inject.internal.Annotations;
 import static com.google.inject.internal.Objects.nonNull;
 import com.google.inject.internal.StackTraceElements;
@@ -27,6 +28,7 @@
 import com.google.inject.matcher.Matcher;
 import com.google.inject.matcher.Matchers;
 import com.google.inject.matcher.AbstractMatcher;
+import com.google.inject.spi.Dependency;
 import com.google.inject.spi.Message;
 import com.google.inject.spi.SourceProviders;
 import com.google.inject.spi.TypeConverter;
@@ -69,6 +71,8 @@
       = new ArrayList<ConstantBindingBuilderImpl>();
   final Map<Class<? extends Annotation>, Scope> scopes =
       new HashMap<Class<? extends Annotation>, Scope>();
+  final List<BindingFactory<?>> bindingFactories
+      = new ArrayList<BindingFactory<?>>();
 
   final List<StaticInjection> staticInjections
       = new ArrayList<StaticInjection>();
@@ -363,6 +367,24 @@
     return constantBuilder;
   }
 
+  @SuppressWarnings("unchecked")
+  public void bind(final Matcher<? super Dependency<?>> dependencyMatcher,
+      final BindingFactory<?> bindingFactory) {
+
+    bindingFactories.add(new BindingFactory() {
+      public boolean bind(Dependency dependency, LinkedBindingBuilder lbb) {
+        if (dependencyMatcher.matches((Dependency<?>)dependency)) {
+          try {
+            return bindingFactory.bind(dependency, lbb);
+          } catch (Exception e) {
+            addError(e);
+          }
+        }
+        return false;
+      }
+    });
+  }
+
   public void requestStaticInjection(Class<?>... types) {
     staticInjections.add(new StaticInjection(source(), types));
   }
@@ -442,10 +464,23 @@
 
     stopwatch.resetAndLog(logger, "Binding indexing");
 
-    for (CreationListener creationListener : creationListeners) {
-      creationListener.notify(injector);
+    if (bindingFactories.size() > 0) {
+      injector.setMissingDependencyHandler(bindingFactoryHandler);
     }
 
+    while (creationListeners.size() > 0) {
+      // need to copy list as we may be adding bindings during this loop
+      CreationListener[] cachedCreationListeners = creationListeners.toArray(
+          new CreationListener[creationListeners.size()]);
+
+      creationListeners.clear();
+      for (CreationListener creationListener : cachedCreationListeners) {
+        creationListener.notify(injector);
+      }
+    }
+
+    injector.setMissingDependencyHandler(null);
+
     stopwatch.resetAndLog(logger, "Validation");
 
     for (StaticInjection staticInjection : staticInjections) {
@@ -622,6 +657,29 @@
   }
 
   /**
+   * Handles missing dependencies by consulting binding factories.
+   */
+  MissingDependencyHandler bindingFactoryHandler =
+      new MissingDependencyHandler() {
+
+    @SuppressWarnings("unchecked")
+    public boolean handle(Dependency<?> dependency) {
+      BindingBuilderImpl<?> builder = bind(dependency.getKey());
+
+      // search in order of registration...
+      for (BindingFactory bindingFactory : bindingFactories) {
+        if (bindingFactory.bind(dependency, builder)) {
+          // register this as a fixed binding
+          putBinding(builder.build(injector));
+          return true;
+        }
+      }
+
+      return false;
+    }
+  };
+
+  /**
    * A requested static injection.
    */
   class StaticInjection {