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 org.jspecify.annotations.Nullable;
024
025/**
026 * Represents a method or constructor parameter.
027 *
028 * @author Ben Yu
029 * @since 14.0
030 */
031public final class Parameter implements AnnotatedElement {
032
033  private final Invokable<?, ?> declaration;
034  private final int position;
035  private final TypeToken<?> type;
036  private final ImmutableList<Annotation> annotations;
037
038  /**
039   * An {@code AnnotatedType} instance, or {@code null} under Android VMs (possible only when using
040   * the Android flavor of Guava). The field is declared with a type of {@code Object} to avoid
041   * compatibility problems on Android VMs. The corresponding accessor method, however, can have the
042   * more specific return type as long as users are careful to guard calls to it with version checks
043   * or reflection: Android VMs ignore the types of elements that aren't used.
044   */
045  private final @Nullable Object annotatedType;
046
047  Parameter(
048      Invokable<?, ?> declaration,
049      int position,
050      TypeToken<?> type,
051      Annotation[] annotations,
052      @Nullable Object annotatedType) {
053    this.declaration = declaration;
054    this.position = position;
055    this.type = type;
056    this.annotations = ImmutableList.copyOf(annotations);
057    this.annotatedType = annotatedType;
058  }
059
060  /** Returns the type of the parameter. */
061  public TypeToken<?> getType() {
062    return type;
063  }
064
065  /** Returns the {@link Invokable} that declares this parameter. */
066  public Invokable<?, ?> getDeclaringInvokable() {
067    return declaration;
068  }
069
070  @Override
071  public boolean isAnnotationPresent(Class<? extends Annotation> annotationType) {
072    return getAnnotation(annotationType) != null;
073  }
074
075  @Override
076  public <A extends Annotation> @Nullable A getAnnotation(Class<A> annotationType) {
077    checkNotNull(annotationType);
078    for (Annotation annotation : annotations) {
079      if (annotationType.isInstance(annotation)) {
080        return annotationType.cast(annotation);
081      }
082    }
083    return null;
084  }
085
086  @Override
087  public Annotation[] getAnnotations() {
088    return getDeclaredAnnotations();
089  }
090
091  /**
092   * @since 18.0
093   */
094  @Override
095  public <A extends Annotation> A[] getAnnotationsByType(Class<A> annotationType) {
096    return getDeclaredAnnotationsByType(annotationType);
097  }
098
099  /**
100   * @since 18.0
101   */
102  @Override
103  public Annotation[] getDeclaredAnnotations() {
104    return annotations.toArray(new Annotation[0]);
105  }
106
107  /**
108   * @since 18.0
109   */
110  @Override
111  public <A extends Annotation> @Nullable A getDeclaredAnnotation(Class<A> annotationType) {
112    checkNotNull(annotationType);
113    return FluentIterable.from(annotations).filter(annotationType).first().orNull();
114  }
115
116  /**
117   * @since 18.0
118   */
119  @Override
120  public <A extends Annotation> A[] getDeclaredAnnotationsByType(Class<A> annotationType) {
121    @Nullable A[] result =
122        FluentIterable.from(annotations).filter(annotationType).toArray(annotationType);
123    @SuppressWarnings("nullness") // safe because the input list contains no nulls
124    A[] cast = (A[]) result;
125    return cast;
126  }
127
128  @Override
129  public boolean equals(@Nullable Object obj) {
130    if (obj instanceof Parameter) {
131      Parameter that = (Parameter) obj;
132      return position == that.position && declaration.equals(that.declaration);
133    }
134    return false;
135  }
136
137  @Override
138  public int hashCode() {
139    return position;
140  }
141
142  @Override
143  public String toString() {
144    return type + " arg" + position;
145  }
146}