src/com/google/inject/matcher/Matchers.java

/**
 * 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.matcher;

import java.io.Serializable;
import java.lang.annotation.Annotation;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Method;
import static com.google.common.base.Preconditions.checkNotNull;

/**
 * Matcher implementations. Supports matching classes and methods.
 *
 * @author crazybob@google.com (Bob Lee)
 */
public class Matchers {
  private Matchers() {}

  /**
   * Returns a matcher which matches any input.
   */
  public static Matcher<Object> any() {
    return ANY;
  }

  private static final Matcher<Object> ANY = new Any();

  private static class Any extends AbstractMatcher<Object> implements Serializable {
    public boolean matches(Object o) {
      return true;
    }

    @Override public String toString() {
      return "any()";
    }

    public Object readResolve() {
      return any();
    }
  }

  /**
   * Inverts the given matcher.
   */
  public static <T> Matcher<T> not(final Matcher<? super T> p) {
    return new Not<T>(p);
  }

  private static class Not<T> extends AbstractMatcher<T> implements Serializable {
    final Matcher<? super T> delegate;

    private Not(Matcher<? super T> delegate) {
      this.delegate = checkNotNull(delegate, "delegate");
    }

    public boolean matches(T t) {
      return !delegate.matches(t);
    }

    @Override public boolean equals(Object other) {
      return other instanceof Not
          && ((Not) other).delegate.equals(delegate);
    }

    @Override public int hashCode() {
      return -delegate.hashCode();
    }

    @Override public String toString() {
      return "not(" + delegate + ")";
    }
  }

  private static void checkForRuntimeRetention(
      Class<? extends Annotation> annotationType) {
    Retention retention = annotationType.getAnnotation(Retention.class);
    if (retention == null || retention.value() != RetentionPolicy.RUNTIME) {
      throw new IllegalArgumentException("Annotation "
          + annotationType.getSimpleName() + " is missing RUNTIME retention");
    }
  }

  /**
   * Returns a matcher which matches elements (methods, classes, etc.)
   * with a given annotation.
   */
  public static Matcher<AnnotatedElement> annotatedWith(
      final Class<? extends Annotation> annotationType) {
    return new AnnotatedWithType(annotationType);
  }

  private static class AnnotatedWithType extends AbstractMatcher<AnnotatedElement>
      implements Serializable {
    private final Class<? extends Annotation> annotationType;

    public AnnotatedWithType(Class<? extends Annotation> annotationType) {
      this.annotationType = checkNotNull(annotationType, "annotation type");
      checkForRuntimeRetention(annotationType);
    }

    public boolean matches(AnnotatedElement element) {
      return element.getAnnotation(annotationType) != null;
    }

    @Override public boolean equals(Object other) {
      return other instanceof AnnotatedWithType
          && ((AnnotatedWithType) other).annotationType.equals(annotationType);
    }

    @Override public int hashCode() {
      return 37 * annotationType.hashCode();
    }

    @Override public String toString() {
      return "annotatedWith(" + annotationType.getSimpleName() + ".class)";
    }
  }

  /**
   * Returns a matcher which matches elements (methods, classes, etc.)
   * with a given annotation.
   */
  public static Matcher<AnnotatedElement> annotatedWith(
      final Annotation annotation) {
    return new AnnotatedWith(annotation);
  }

  private static class AnnotatedWith extends AbstractMatcher<AnnotatedElement>
      implements Serializable {
    private final Annotation annotation;

    public AnnotatedWith(Annotation annotation) {
      this.annotation = checkNotNull(annotation, "annotation");
      checkForRuntimeRetention(annotation.annotationType());
    }

    public boolean matches(AnnotatedElement element) {
      Annotation fromElement = element.getAnnotation(annotation.annotationType());
      return fromElement != null && annotation.equals(fromElement);
    }

    @Override public boolean equals(Object other) {
      return other instanceof AnnotatedWith
          && ((AnnotatedWith) other).annotation.equals(annotation);
    }

    @Override public int hashCode() {
      return 37 * annotation.hashCode();
    }

    @Override public String toString() {
      return "annotatedWith(" + annotation + ")";
    }
  }

  /**
   * Returns a matcher which matches subclasses of the given type (as well as
   * the given type).
   */
  public static Matcher<Class> subclassesOf(final Class<?> superclass) {
    return new SubclassesOf(superclass);
  }

  private static class SubclassesOf extends AbstractMatcher<Class>
      implements Serializable {
    private final Class<?> superclass;

    public SubclassesOf(Class<?> superclass) {
      this.superclass = checkNotNull(superclass, "superclass");
    }

    public boolean matches(Class subclass) {
      return superclass.isAssignableFrom(subclass);
    }

    @Override public boolean equals(Object other) {
      return other instanceof SubclassesOf
          && ((SubclassesOf) other).superclass.equals(superclass);
    }

    @Override public int hashCode() {
      return 37 * superclass.hashCode();
    }

    @Override public String toString() {
      return "subclassesOf(" + superclass.getSimpleName() + ".class)";
    }
  }

  /**
   * Returns a matcher which matches objects equal to the given object.
   */
  public static Matcher<Object> only(Object value) {
    return new Only(value);
  }

  private static class Only extends AbstractMatcher<Object>
      implements Serializable {
    private final Object value;

    public Only(Object value) {
      this.value = checkNotNull(value, "value");
    }

    public boolean matches(Object other) {
      return value.equals(other);
    }

    @Override public boolean equals(Object other) {
      return other instanceof Only
          && ((Only) other).value.equals(value);
    }

    @Override public int hashCode() {
      return 37 * value.hashCode();
    }

    @Override public String toString() {
      return "only(" + value + ")";
    }
  }

  /**
   * Returns a matcher which matches only the given object.
   */
  public static Matcher<Object> identicalTo(final Object value) {
    return new IdenticalTo(value);
  }

  private static class IdenticalTo extends AbstractMatcher<Object>
      implements Serializable {
    private final Object value;

    public IdenticalTo(Object value) {
      this.value = checkNotNull(value, "value");
    }

    public boolean matches(Object other) {
      return value == other;
    }

    @Override public boolean equals(Object other) {
      return other instanceof IdenticalTo
          && ((IdenticalTo) other).value == value;
    }

    @Override public int hashCode() {
      return 37 * System.identityHashCode(value);
    }

    @Override public String toString() {
      return "identicalTo(" + value + ")";
    }
  }

  /**
   * Returns a matcher which matches classes in the given package.
   */
  public static Matcher<Class> inPackage(final Package targetPackage) {
    return new InPackage(targetPackage);
  }

  private static class InPackage extends AbstractMatcher<Class> implements Serializable {
    private final transient Package targetPackage;
    private final String packageName;

    public InPackage(Package targetPackage) {
      this.targetPackage = checkNotNull(targetPackage, "package");
      this.packageName = targetPackage.getName();
    }

    public boolean matches(Class c) {
      return c.getPackage().equals(targetPackage);
    }

    @Override public boolean equals(Object other) {
      return other instanceof InPackage
          && ((InPackage) other).targetPackage.equals(targetPackage);
    }

    @Override public int hashCode() {
      return 37 * targetPackage.hashCode();
    }

    @Override public String toString() {
      return "inPackage(" + targetPackage.getName() + ")";
    }

    public Object readResolve() {
      return inPackage(Package.getPackage(packageName));
    }
  }

  /**
   * Returns a matcher which matches methods with matching return types.
   */
  public static Matcher<Method> returns(
      final Matcher<? super Class<?>> returnType) {
    return new Returns(returnType);
  }

  private static class Returns extends AbstractMatcher<Method> implements Serializable {
    private final Matcher<? super Class<?>> returnType;

    public Returns(Matcher<? super Class<?>> returnType) {
      this.returnType = checkNotNull(returnType, "return type matcher");
    }

    public boolean matches(Method m) {
      return returnType.matches(m.getReturnType());
    }

    @Override public boolean equals(Object other) {
      return other instanceof Returns
          && ((Returns) other).returnType.equals(returnType);
    }

    @Override public int hashCode() {
      return 37 * returnType.hashCode();
    }

    @Override public String toString() {
      return "returns(" + returnType + ")";
    }
  }
}