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Java example source code file (InternalInjectorCreator.java)

This example Java source code file (InternalInjectorCreator.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

annotation, assertionerror, binding, collection, errors, initializer, injector, injectorshell, internalinjectorcreator, linkedbindingimpl, map, provider, toolstageinjector, unsupportedoperationexception, util

The InternalInjectorCreator.java Java example source code

/**
 * Copyright (C) 2006 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.internal;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.inject.Binding;
import com.google.inject.Injector;
import com.google.inject.Key;
import com.google.inject.MembersInjector;
import com.google.inject.Module;
import com.google.inject.Provider;
import com.google.inject.Scope;
import com.google.inject.Stage;
import com.google.inject.TypeLiteral;
import com.google.inject.internal.util.Stopwatch;
import com.google.inject.spi.Dependency;
import com.google.inject.spi.TypeConverterBinding;

import java.lang.annotation.Annotation;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Builds a tree of injectors. This is a primary injector, plus child injectors needed for each
 * {@code Binder.newPrivateBinder() private environment}. The primary injector is not necessarily a
 * top-level injector.
 *
 * <p>Injector construction happens in two phases.
 * <ol>
 *   <li>Static building. In this phase, we interpret commands, create bindings, and inspect 
 *     dependencies. During this phase, we hold a lock to ensure consistency with parent injectors.
 *     No user code is executed in this phase.</li>
 *   <li>Dynamic injection. In this phase, we call user code. We inject members that requested
 *     injection. This may require user's objects be created and their providers be called. And we
 *     create eager singletons. In this phase, user code may have started other threads. This phase
 *     is not executed for injectors created using {@link Stage#TOOL the tool stage}</li>
 * </ol>
 *
 * @author crazybob@google.com (Bob Lee)
 * @author jessewilson@google.com (Jesse Wilson)
 */
public final class InternalInjectorCreator {

  private final Stopwatch stopwatch = new Stopwatch();
  private final Errors errors = new Errors();

  private final Initializer initializer = new Initializer();
  private final ProcessedBindingData bindingData;
  private final InjectionRequestProcessor injectionRequestProcessor;

  private final InjectorShell.Builder shellBuilder = new InjectorShell.Builder();
  private List<InjectorShell> shells;
  
  public InternalInjectorCreator() {
    injectionRequestProcessor = new InjectionRequestProcessor(errors, initializer);
    bindingData = new ProcessedBindingData();
  }
  
  public InternalInjectorCreator stage(Stage stage) {
    shellBuilder.stage(stage);
    return this;
  }

  /**
   * Sets the parent of the injector to-be-constructed. As a side effect, this sets this injector's
   * stage to the stage of {@code parent} and sets {@link #requireExplicitBindings()} if the parent
   * injector also required them.
   */
  public InternalInjectorCreator parentInjector(InjectorImpl parent) {
    shellBuilder.parent(parent);
    return this;
  }

  public InternalInjectorCreator addModules(Iterable<? extends Module> modules) {
    shellBuilder.addModules(modules);
    return this;
  }

  public Injector build() {
    if (shellBuilder == null) {
      throw new AssertionError("Already built, builders are not reusable.");
    }

    // Synchronize while we're building up the bindings and other injector state. This ensures that
    // the JIT bindings in the parent injector don't change while we're being built
    synchronized (shellBuilder.lock()) {
      shells = shellBuilder.build(initializer, bindingData, stopwatch, errors);
      stopwatch.resetAndLog("Injector construction");

      initializeStatically();
    }

    injectDynamically();

    if (shellBuilder.getStage() == Stage.TOOL) {
      // wrap the primaryInjector in a ToolStageInjector
      // to prevent non-tool-friendy methods from being called.
      return new ToolStageInjector(primaryInjector());
    } else {
      return primaryInjector();
    }
  }

  /** Initialize and validate everything. */
  private void initializeStatically() {
    bindingData.initializeBindings();
    stopwatch.resetAndLog("Binding initialization");

    for (InjectorShell shell : shells) {
      shell.getInjector().index();
    }
    stopwatch.resetAndLog("Binding indexing");

    injectionRequestProcessor.process(shells);
    stopwatch.resetAndLog("Collecting injection requests");

    bindingData.runCreationListeners(errors);
    stopwatch.resetAndLog("Binding validation");

    injectionRequestProcessor.validate();
    stopwatch.resetAndLog("Static validation");

    initializer.validateOustandingInjections(errors);
    stopwatch.resetAndLog("Instance member validation");

    new LookupProcessor(errors).process(shells);
    for (InjectorShell shell : shells) {
      ((DeferredLookups) shell.getInjector().lookups).initialize(errors);
    }
    stopwatch.resetAndLog("Provider verification");

    for (InjectorShell shell : shells) {
      if (!shell.getElements().isEmpty()) {
        throw new AssertionError("Failed to execute " + shell.getElements());
      }
    }

    errors.throwCreationExceptionIfErrorsExist();
  }

  /**
   * Returns the injector being constructed. This is not necessarily the root injector.
   */
  private Injector primaryInjector() {
    return shells.get(0).getInjector();
  }

  /**
   * Inject everything that can be injected. This method is intentionally not synchronized. If we
   * locked while injecting members (ie. running user code), things would deadlock should the user
   * code build a just-in-time binding from another thread.
   */
  private void injectDynamically() {
    injectionRequestProcessor.injectMembers();
    stopwatch.resetAndLog("Static member injection");

    initializer.injectAll(errors);
    stopwatch.resetAndLog("Instance injection");
    errors.throwCreationExceptionIfErrorsExist();

    if(shellBuilder.getStage() != Stage.TOOL) {
      for (InjectorShell shell : shells) {
        loadEagerSingletons(shell.getInjector(), shellBuilder.getStage(), errors);
      }
      stopwatch.resetAndLog("Preloading singletons");
    }
    errors.throwCreationExceptionIfErrorsExist();
  }

  /**
   * Loads eager singletons, or all singletons if we're in Stage.PRODUCTION. Bindings discovered
   * while we're binding these singletons are not be eager.
   */
  void loadEagerSingletons(InjectorImpl injector, Stage stage, final Errors errors) {
    @SuppressWarnings("unchecked") // casting Collection<Binding> to Collection is safe
    Iterable<BindingImpl candidateBindings = ImmutableList.copyOf(Iterables.concat(
        (Collection) injector.state.getExplicitBindingsThisLevel().values(),
        injector.jitBindings.values()));
    for (final BindingImpl<?> binding : candidateBindings) {
      if (isEagerSingleton(injector, binding, stage)) {
        try {
          injector.callInContext(new ContextualCallable<Void>() {
            Dependency<?> dependency = Dependency.get(binding.getKey());
            public Void call(InternalContext context) {
              Dependency previous = context.pushDependency(dependency, binding.getSource());
              Errors errorsForBinding = errors.withSource(dependency);
              try {
                binding.getInternalFactory().get(errorsForBinding, context, dependency, false);
              } catch (ErrorsException e) {
                errorsForBinding.merge(e.getErrors());
              } finally {
                context.popStateAndSetDependency(previous);
              }

              return null;
            }
          });
        } catch (ErrorsException e) {
          throw new AssertionError();
        }
      }
    }
  }

  private boolean isEagerSingleton(InjectorImpl injector, BindingImpl<?> binding, Stage stage) {
    if (binding.getScoping().isEagerSingleton(stage)) {
      return true;
    }

    // handle a corner case where a child injector links to a binding in a parent injector, and
    // that binding is singleton. We won't catch this otherwise because we only iterate the child's
    // bindings.
    if (binding instanceof LinkedBindingImpl) {
      Key<?> linkedBinding = ((LinkedBindingImpl) binding).getLinkedKey();
      return isEagerSingleton(injector, injector.getBinding(linkedBinding), stage);
    }

    return false;
  }

  /** {@link Injector} exposed to users in {@link Stage#TOOL}. */
  static class ToolStageInjector implements Injector {
    private final Injector delegateInjector;
    
    ToolStageInjector(Injector delegateInjector) {
      this.delegateInjector = delegateInjector;
    }
    public void injectMembers(Object o) {
      throw new UnsupportedOperationException(
        "Injector.injectMembers(Object) is not supported in Stage.TOOL");
    }
    public Map<Key> getBindings() {
      return this.delegateInjector.getBindings();
    }
    public Map<Key> getAllBindings() {
      return this.delegateInjector.getAllBindings();
    }
    public <T> Binding getBinding(Key key) {
      return this.delegateInjector.getBinding(key);
    }
    public <T> Binding getBinding(Class type) {
      return this.delegateInjector.getBinding(type);
    }
    public <T> Binding getExistingBinding(Key key) {
      return this.delegateInjector.getExistingBinding(key);
    }
    public <T> List> findBindingsByType(TypeLiteral type) {
      return this.delegateInjector.findBindingsByType(type);
    }
    public Injector getParent() {
      return delegateInjector.getParent();
    }
    public Injector createChildInjector(Iterable<? extends Module> modules) {
      return delegateInjector.createChildInjector(modules);
    }
    public Injector createChildInjector(Module... modules) {
      return delegateInjector.createChildInjector(modules);
    }
    public Map<Class getScopeBindings() {
      return delegateInjector.getScopeBindings();
    }
    public Set<TypeConverterBinding> getTypeConverterBindings() {
      return delegateInjector.getTypeConverterBindings();
    }
    public <T> Provider getProvider(Key key) {
      throw new UnsupportedOperationException(
        "Injector.getProvider(Key<T>) is not supported in Stage.TOOL");
    }
    public <T> Provider getProvider(Class type) {
      throw new UnsupportedOperationException(
        "Injector.getProvider(Class<T>) is not supported in Stage.TOOL");
    }
    public <T> MembersInjector getMembersInjector(TypeLiteral typeLiteral) {
      throw new UnsupportedOperationException(
        "Injector.getMembersInjector(TypeLiteral<T>) is not supported in Stage.TOOL");
    }
    public <T> MembersInjector getMembersInjector(Class type) {
      throw new UnsupportedOperationException(
        "Injector.getMembersInjector(Class<T>) is not supported in Stage.TOOL");
    }
    public <T> T getInstance(Key key) {
      throw new UnsupportedOperationException(
        "Injector.getInstance(Key<T>) is not supported in Stage.TOOL");
    }
    public <T> T getInstance(Class type) {
      throw new UnsupportedOperationException(
        "Injector.getInstance(Class<T>) is not supported in Stage.TOOL");
    }
  }
}

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