001/*
002 * Copyright (C) 2012 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.reflect;
016
017import static com.google.common.base.Preconditions.checkNotNull;
018
019import com.google.common.collect.FluentIterable;
020import com.google.common.collect.ImmutableList;
021import java.lang.annotation.Annotation;
022import java.lang.reflect.AnnotatedElement;
023import javax.annotation.CheckForNull;
024import org.checkerframework.checker.nullness.qual.Nullable;
025
026/**
027 * Represents a method or constructor parameter.
028 *
029 * @author Ben Yu
030 * @since 14.0
031 */
032public final class Parameter implements AnnotatedElement {
033
034  private final Invokable<?, ?> declaration;
035  private final int position;
036  private final TypeToken<?> type;
037  private final ImmutableList<Annotation> annotations;
038
039  /**
040   * An {@code AnnotatedType} instance, or {@code null} under Android VMs (possible only when using
041   * the Android flavor of Guava). The field is declared with a type of {@code Object} to avoid
042   * compatibility problems on Android VMs. The corresponding accessor method, however, can have the
043   * more specific return type as long as users are careful to guard calls to it with version checks
044   * or reflection: Android VMs ignore the types of elements that aren't used.
045   */
046  private final @Nullable Object annotatedType;
047
048  Parameter(
049      Invokable<?, ?> declaration,
050      int position,
051      TypeToken<?> type,
052      Annotation[] annotations,
053      @Nullable Object annotatedType) {
054    this.declaration = declaration;
055    this.position = position;
056    this.type = type;
057    this.annotations = ImmutableList.copyOf(annotations);
058    this.annotatedType = annotatedType;
059  }
060
061  /** Returns the type of the parameter. */
062  public TypeToken<?> getType() {
063    return type;
064  }
065
066  /** Returns the {@link Invokable} that declares this parameter. */
067  public Invokable<?, ?> getDeclaringInvokable() {
068    return declaration;
069  }
070
071  @Override
072  public boolean isAnnotationPresent(Class<? extends Annotation> annotationType) {
073    return getAnnotation(annotationType) != null;
074  }
075
076  @Override
077  @CheckForNull
078  public <A extends Annotation> A getAnnotation(Class<A> annotationType) {
079    checkNotNull(annotationType);
080    for (Annotation annotation : annotations) {
081      if (annotationType.isInstance(annotation)) {
082        return annotationType.cast(annotation);
083      }
084    }
085    return null;
086  }
087
088  @Override
089  public Annotation[] getAnnotations() {
090    return getDeclaredAnnotations();
091  }
092
093  /**
094   * @since 18.0
095   */
096  @Override
097  public <A extends Annotation> A[] getAnnotationsByType(Class<A> annotationType) {
098    return getDeclaredAnnotationsByType(annotationType);
099  }
100
101  /** @since 18.0 */
102  @Override
103  public Annotation[] getDeclaredAnnotations() {
104    return annotations.toArray(new Annotation[0]);
105  }
106
107  /**
108   * @since 18.0
109   */
110  @Override
111  @CheckForNull
112  public <A extends Annotation> A getDeclaredAnnotation(Class<A> annotationType) {
113    checkNotNull(annotationType);
114    return FluentIterable.from(annotations).filter(annotationType).first().orNull();
115  }
116
117  /**
118   * @since 18.0
119   */
120  @Override
121  public <A extends Annotation> A[] getDeclaredAnnotationsByType(Class<A> annotationType) {
122    @Nullable
123    A[] result = FluentIterable.from(annotations).filter(annotationType).toArray(annotationType);
124    @SuppressWarnings("nullness") // safe because the input list contains no nulls
125    A[] cast = (A[]) result;
126    return cast;
127  }
128
129  @Override
130  public boolean equals(@CheckForNull Object obj) {
131    if (obj instanceof Parameter) {
132      Parameter that = (Parameter) obj;
133      return position == that.position && declaration.equals(that.declaration);
134    }
135    return false;
136  }
137
138  @Override
139  public int hashCode() {
140    return position;
141  }
142
143  @Override
144  public String toString() {
145    return type + " arg" + position;
146  }
147}