injectorimpl.java

Guice是轻量级的依赖注入框架。简而言之

    }

    // Add injectors for superclass first.
    addInjectors(clazz.getSuperclass(), injectors);

    // TODO (crazybob): Filter out overridden members.
    addSingleInjectorsForFields(clazz.getDeclaredFields(), false, injectors);
    addSingleInjectorsForMethods(clazz.getDeclaredMethods(), false, injectors);
  }

  void addSingleInjectorsForMethods(Method[] methods, boolean statics,
      List<SingleMemberInjector> injectors) {
    addInjectorsForMembers(Arrays.asList(methods), statics, injectors,
        new SingleInjectorFactory<Method>() {
          public SingleMemberInjector create(InjectorImpl injector,
              Method method) throws MissingDependencyException {
            return new SingleMethodInjector(injector, method);
          }
        });
  }

  void addSingleInjectorsForFields(Field[] fields, boolean statics,
      List<SingleMemberInjector> injectors) {
    addInjectorsForMembers(Arrays.asList(fields), statics, injectors,
        new SingleInjectorFactory<Field>() {
          public SingleMemberInjector create(InjectorImpl injector,
              Field field) throws MissingDependencyException {
            return new SingleFieldInjector(injector, field);
          }
        });
  }

  <M extends Member & AnnotatedElement> void addInjectorsForMembers(
      List<M> members, boolean statics, List<SingleMemberInjector> injectors,
      SingleInjectorFactory<M> injectorFactory) {
    for (M member : members) {
      if (isStatic(member) == statics) {
        Inject inject = member.getAnnotation(Inject.class);
        if (inject != null) {
          try {
            injectors.add(injectorFactory.create(this, member));
          }
          catch (MissingDependencyException e) {
            if (!inject.optional()) {
              // TODO: Report errors for more than one parameter per member.
              e.handle(errorHandler);
            }
          }
        }
      }
    }
  }

  Map<Key<?>, BindingImpl<?>> internalBindings() {
    return bindings;
  }

  // not test-covered
  public Map<Key<?>, Binding<?>> getBindings() {
    return Collections.<Key<?>, Binding<?>>unmodifiableMap(bindings);
  }

  @SuppressWarnings("unchecked")
  public <T> BindingImpl<T> getBinding(Key<T> key) {
    return (BindingImpl<T>) bindings.get(key);
  }

  interface SingleInjectorFactory<M extends Member & AnnotatedElement> {
    SingleMemberInjector create(InjectorImpl injector, M member)
        throws MissingDependencyException;
  }

  private boolean isStatic(Member member) {
    return Modifier.isStatic(member.getModifiers());
  }

  private static class BindingsMultimap {
    private final Map<TypeLiteral<?>, List<? extends BindingImpl<?>>> map
        = new HashMap<TypeLiteral<?>, List<? extends BindingImpl<?>>>();

    public <T> void put(TypeLiteral<T> type, BindingImpl<T> binding) {
      List<BindingImpl<T>> bindingsForThisType = getFromMap(type);
      if (bindingsForThisType == null) {
        bindingsForThisType = new ArrayList<BindingImpl<T>>();
        // We only put matching entries into the map
        map.put(type, bindingsForThisType);
      }
      bindingsForThisType.add(binding);
    }

    public <T> List<BindingImpl<T>> getAll(TypeLiteral<T> type) {
      List<BindingImpl<T>> list = getFromMap(type);
      return list == null ? Collections.<BindingImpl<T>>emptyList() : list;
    }

    // safe because we only put matching entries into the map
    @SuppressWarnings("unchecked")
    private <T> List<BindingImpl<T>> getFromMap(TypeLiteral<T> type) {
      return (List<BindingImpl<T>>) map.get(type);
    }
  }

  class SingleFieldInjector implements SingleMemberInjector {

    final Field field;
    final InternalFactory<?> factory;
    final ExternalContext<?> externalContext;

    public SingleFieldInjector(InjectorImpl injector, Field field)
        throws MissingDependencyException {
      this.field = field;

      // Ewwwww...
      field.setAccessible(true);

      Key<?> key = Key.get(
          field.getGenericType(), field, field.getAnnotations(), errorHandler);
      factory = injector.getInternalFactory(field, key);
      if (factory == null) {
        throw new MissingDependencyException(key, field);
      }

      this.externalContext = ExternalContext.newInstance(field, key, injector);
    }

    public void inject(InternalContext context, Object o) {
      ExternalContext<?> previous = context.getExternalContext();
      context.setExternalContext(externalContext);
      try {
        Object value = factory.get(context);
        if (value == null) {
          throw new AssertionError(); // we should have prevented this
        }
        field.set(o, value);
      }
      catch (IllegalAccessException e) {
        throw new AssertionError(e);
      }
      catch (ConfigurationException e) {
        throw e;
      }
      catch (Throwable throwable) {
        throw new ProvisionException(externalContext, throwable);
      }
      finally {
        context.setExternalContext(previous);
      }
    }
  }

  /**
   * Gets parameter injectors.
   *
   * @param member to which the parameters belong
   * @param annotations on the parameters
   * @param parameterTypes parameter types
   * @return injections
   */
  <M extends AccessibleObject & Member>
  SingleParameterInjector<?>[] getParametersInjectors(M member,
      Annotation[][] annotations, Type[] parameterTypes)
      throws MissingDependencyException {
    SingleParameterInjector<?>[] parameterInjectors
        = new SingleParameterInjector<?>[parameterTypes.length];
    Iterator<Annotation[]> annotationsIterator
        = Arrays.asList(annotations).iterator();
    int index = 0;
    for (Type parameterType : parameterTypes) {
      Annotation[] parameterAnnotations = annotationsIterator.next();
      Key<?> key = Key.get(
          parameterType, member, parameterAnnotations, errorHandler);
      parameterInjectors[index] = createParameterInjector(key, member, index);
      index++;
    }

    return parameterInjectors;
  }

  <T> SingleParameterInjector<T> createParameterInjector(
      Key<T> key, Member member, int index) throws MissingDependencyException {
    InternalFactory<? extends T> factory = getInternalFactory(member, key);
    if (factory == null) {
      throw new MissingDependencyException(key, member);
    }

    ExternalContext<T> externalContext
        = ExternalContext.newInstance(member, index, key, this);
    return new SingleParameterInjector<T>(externalContext, factory);
  }

  static class SingleMethodInjector implements SingleMemberInjector {

    final MethodInvoker methodInvoker;
    final SingleParameterInjector<?>[] parameterInjectors;

    public SingleMethodInjector(InjectorImpl injector, final Method method)
        throws MissingDependencyException {
      // We can't use FastMethod if the method is private.
      if (Modifier.isPrivate(method.getModifiers())
          || Modifier.isProtected(method.getModifiers())) {
        method.setAccessible(true);
        this.methodInvoker = new MethodInvoker() {
          public Object invoke(Object target, Object... parameters) throws
              IllegalAccessException, InvocationTargetException {
            Objects.assertNoNulls(parameters);
            return method.invoke(target, parameters);
          }
        };
      }
      else {
        FastClass fastClass = GuiceFastClass.create(method.getDeclaringClass());
        final FastMethod fastMethod = fastClass.getMethod(method);

        this.methodInvoker = new MethodInvoker() {
          public Object invoke(Object target, Object... parameters)
          throws IllegalAccessException, InvocationTargetException {
            Objects.assertNoNulls(parameters);
            return fastMethod.invoke(target, parameters);
          }
        };
      }

      Type[] parameterTypes = method.getGenericParameterTypes();
      parameterInjectors = parameterTypes.length > 0
          ? injector.getParametersInjectors(
              method, method.getParameterAnnotations(), parameterTypes)
          : null;
    }

    public void inject(InternalContext context, Object o) {
      try {
        methodInvoker.invoke(o, getParameters(context, parameterInjectors));
      }
      catch (Exception e) {
        throw new RuntimeException(e);
      }
    }
  }

  /**
   * Invokes a method.
   */
  interface MethodInvoker {
    Object invoke(Object target, Object... parameters) throws
        IllegalAccessException, InvocationTargetException;
  }

  final Map<Class<?>, ConstructorInjector> constructors
      = new ReferenceCache<Class<?>, ConstructorInjector>() {
    @SuppressWarnings("unchecked")
    protected ConstructorInjector<?> create(Class<?> implementation) {
      if (implementation.isInterface()) {
        errorHandler.handle(defaultSource,
            ErrorMessages.CANNOT_INJECT_ABSTRACT_TYPE, implementation);
        return ConstructorInjector.invalidConstructor();
      }

      return new ConstructorInjector(InjectorImpl.this, implementation);
    }
  };

  /**
   * A placeholder. This enables us to continue processing and gather more
   * errors but blows up if you actually try to use it.
   */
  static class InvalidConstructor {
    InvalidConstructor() {
      throw new AssertionError();
    }
  }

  @SuppressWarnings("unchecked")
  static <T> Constructor<T> invalidConstructor() {
    try {
      return (Constructor<T>) InvalidConstructor.class.getDeclaredConstructor();
    }
    catch (NoSuchMethodException e) {
      throw new AssertionError(e);
    }
  }

  static class SingleParameterInjector<T> {

    final ExternalContext<T> externalContext;
    final InternalFactory<? extends T> factory;

    public SingleParameterInjector(ExternalContext<T> externalContext,
        InternalFactory<? extends T> factory) {
      this.externalContext = externalContext;
      this.factory = factory;
    }

    T inject(InternalContext context) {
      ExternalContext<?> previous = context.getExternalContext();
      context.setExternalContext(externalContext);
      try {
        return factory.get(context);
      }
      catch (ConfigurationException e) {
        throw e;
      }
      catch (Throwable throwable) {
        throw new ProvisionException(externalContext, throwable);
      }
      finally {
        context.setExternalContext(previous);
      }
    }
  }

  /**
   * Iterates over parameter injectors and creates an array of parameter
   * values.
   */
  static Object[] getParameters(InternalContext context,
      SingleParameterInjector[] parameterInjectors) {
    if (parameterInjectors == null) {
      return null;
    }

    Object[] parameters = new Object[parameterInjectors.length];
    for (int i = 0; i < parameters.length; i++) {
      parameters[i] = parameterInjectors[i].inject(context);
    }
    return parameters;
  }

  void injectMembers(Object o, InternalContext context) {
    List<SingleMemberInjector> injectorsForClass = injectors.get(o.getClass());
    for (SingleMemberInjector injector : injectorsForClass) {
      injector.inject(context, o);
    }
  }

  // Not test-covered
  public void injectMembers(final Object o) {
    callInContext(new ContextualCallable<Void>() {
      public Void call(InternalContext context) {
        injectMembers(o, context);
        return null;
      }
    });
  }