constantbindingbuilderimpl.java

Guice是轻量级的依赖注入框架。简而言之

/*
 * 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.Key.AnnotationStrategy;
import com.google.inject.binder.ConstantBindingBuilder;
import com.google.inject.binder.AnnotatedConstantBindingBuilder;
import com.google.inject.spi.SourceProviders;
import com.google.inject.util.Annotations;
import com.google.inject.util.StackTraceElements;
import com.google.inject.util.Objects;
import java.lang.annotation.Annotation;

/**
   * Builds a constant binding.
 */
class ConstantBindingBuilderImpl implements AnnotatedConstantBindingBuilder,
    ConstantBindingBuilder {

  BindingInfo<?> bindingInfo;
  AnnotationStrategy annotationStrategy;
  final Object source;
  private BinderImpl binder;

  ConstantBindingBuilderImpl(BinderImpl binder, Object source) {
    this.binder = binder;
    this.source = source;
  }

  public ConstantBindingBuilder annotatedWith(
      Class<? extends Annotation> annotationType) {
    Objects.nonNull(annotationType, "annotation type");
    validateAnnotation(annotationType);
    annotationStrategy = Key.strategyFor(annotationType);
    return this;
  }

  public ConstantBindingBuilder annotatedWith(Annotation annotation) {
    Objects.nonNull(annotation, "annotation");
    validateAnnotation(annotation.annotationType());
    annotationStrategy = Key.strategyFor(annotation);
    return this;
  }

  void validateAnnotation(Class<? extends Annotation> annotationType) {
    if (annotationStrategy != null) {
      binder.addError(source, ErrorMessages.ANNOTATION_ALREADY_SPECIFIED);
      return;
    }

    boolean retainedAtRuntime =
        Annotations.isRetainedAtRuntime(annotationType);
    boolean bindingAnnotation = Key.isBindingAnnotation(annotationType);

    if (!retainedAtRuntime) {
      binder.addError(StackTraceElements.forType(annotationType),
          ErrorMessages.MISSING_RUNTIME_RETENTION, source);
    }

    if (!bindingAnnotation) {
      binder.addError(StackTraceElements.forType(annotationType),
          ErrorMessages.MISSING_BINDING_ANNOTATION, source);
    }
  }

  boolean hasValue() {
    return bindingInfo != null;
  }

  Object getSource() {
    return source;
  }

  public void to(String value) {
    to(String.class, value);
  }

  public void to(int value) {
    to(int.class, value);
  }

  public void to(long value) {
    to(long.class, value);
  }

  public void to(boolean value) {
    to(boolean.class, value);
  }

  public void to(double value) {
    to(double.class, value);
  }

  public void to(float value) {
    to(float.class, value);
  }

  public void to(short value) {
    to(short.class, value);
  }

  public void to(char value) {
    to(char.class, value);
  }

  public void to(Class<?> value) {
    to(Class.class, value);
  }

  public <E extends Enum<E>> void to(E value) {
    to(value.getDeclaringClass(), value);
  }

  /**
   * Maps a constant value to the given type and name.
   */
  <T> void to(final Class<T> type, final T value) {
    if (this.bindingInfo != null) {
      binder.addError(source, ErrorMessages.CONSTANT_VALUE_ALREADY_SET);
    } else {
      this.bindingInfo
          = new BindingInfo<T>(type, value, annotationStrategy, source);
    }
  }

  BindingImpl<?> createBinding(InjectorImpl injector) {
    return bindingInfo.createBinding(injector);
  }

  private static class BindingInfo<T> {

    final Class<T> type;
    final T value;
    final AnnotationStrategy annotationStrategy;
    final Object source;

    BindingInfo(Class<T> type, T value,
        AnnotationStrategy annotationStrategy, Object source) {
      this.type = type;
      this.value = value;
      this.annotationStrategy = annotationStrategy;
      this.source = source;
    }

    BindingImpl<T> createBinding(InjectorImpl injector) {
      Key<T> key = Key.get(type, annotationStrategy);
      ConstantFactory<T> factory = new ConstantFactory<T>(value);
      return BindingImpl.newInstance(injector, key, source, factory);
    }
  }
}