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/*
 * Copyright (C) 2012 The Guava Authors
 *
 * 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.common.reflect;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.Beta;
import com.google.common.collect.ImmutableList;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.lang.annotation.Annotation;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Constructor;
import java.lang.reflect.GenericDeclaration;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.Arrays;
import javax.annotation.Nullable;

/**
 * Wrapper around either a {@link Method} or a {@link Constructor}. Convenience API is provided to
 * make common reflective operation easier to deal with, such as {@link #isPublic},
 * {@link #getParameters} etc.
 *
 * 

In addition to convenience methods, {@link TypeToken#method} and {@link TypeToken#constructor} * will resolve the type parameters of the method or constructor in the context of the owner type, * which may be a subtype of the declaring class. For example: * *

   {@code
 *   Method getMethod = List.class.getMethod("get", int.class);
 *   Invokable, ?> invokable = new TypeToken>() {}.method(getMethod);
 *   assertEquals(TypeToken.of(String.class), invokable.getReturnType()); // Not Object.class!
 *   assertEquals(new TypeToken>() {}, invokable.getOwnerType());}
* * @param the type that owns this method or constructor. * @param the return type of (or supertype thereof) the method or the declaring type of the * constructor. * @author Ben Yu * @since 14.0 */ @Beta public abstract class Invokable extends Element implements GenericDeclaration { Invokable(M member) { super(member); } /** Returns {@link Invokable} of {@code method}. */ public static Invokable from(Method method) { return new MethodInvokable<>(method); } /** Returns {@link Invokable} of {@code constructor}. */ public static Invokable from(Constructor constructor) { return new ConstructorInvokable(constructor); } /** * Returns {@code true} if this is an overridable method. Constructors, private, static or final * methods, or methods declared by final classes are not overridable. */ public abstract boolean isOverridable(); /** Returns {@code true} if this was declared to take a variable number of arguments. */ public abstract boolean isVarArgs(); /** * Invokes with {@code receiver} as 'this' and {@code args} passed to the underlying method and * returns the return value; or calls the underlying constructor with {@code args} and returns the * constructed instance. * * @throws IllegalAccessException if this {@code Constructor} object enforces Java language access * control and the underlying method or constructor is inaccessible. * @throws IllegalArgumentException if the number of actual and formal parameters differ; if an * unwrapping conversion for primitive arguments fails; or if, after possible unwrapping, a * parameter value cannot be converted to the corresponding formal parameter type by a method * invocation conversion. * @throws InvocationTargetException if the underlying method or constructor throws an exception. */ // All subclasses are owned by us and we'll make sure to get the R type right. @SuppressWarnings("unchecked") @CanIgnoreReturnValue public final R invoke(@Nullable T receiver, Object... args) throws InvocationTargetException, IllegalAccessException { return (R) invokeInternal(receiver, checkNotNull(args)); } /** Returns the return type of this {@code Invokable}. */ // All subclasses are owned by us and we'll make sure to get the R type right. @SuppressWarnings("unchecked") public final TypeToken getReturnType() { return (TypeToken) TypeToken.of(getGenericReturnType()); } /** * Returns all declared parameters of this {@code Invokable}. Note that if this is a constructor * of a non-static inner class, unlike {@link Constructor#getParameterTypes}, the hidden * {@code this} parameter of the enclosing class is excluded from the returned parameters. */ public final ImmutableList getParameters() { Type[] parameterTypes = getGenericParameterTypes(); Annotation[][] annotations = getParameterAnnotations(); ImmutableList.Builder builder = ImmutableList.builder(); for (int i = 0; i < parameterTypes.length; i++) { builder.add(new Parameter(this, i, TypeToken.of(parameterTypes[i]), annotations[i])); } return builder.build(); } /** Returns all declared exception types of this {@code Invokable}. */ public final ImmutableList> getExceptionTypes() { ImmutableList.Builder> builder = ImmutableList.builder(); for (Type type : getGenericExceptionTypes()) { // getGenericExceptionTypes() will never return a type that's not exception @SuppressWarnings("unchecked") TypeToken exceptionType = (TypeToken) TypeToken.of(type); builder.add(exceptionType); } return builder.build(); } /** * Explicitly specifies the return type of this {@code Invokable}. For example: *
   {@code
   *   Method factoryMethod = Person.class.getMethod("create");
   *   Invokable factory = Invokable.of(getNameMethod).returning(Person.class);}
*/ public final Invokable returning(Class returnType) { return returning(TypeToken.of(returnType)); } /** Explicitly specifies the return type of this {@code Invokable}. */ public final Invokable returning(TypeToken returnType) { if (!returnType.isSupertypeOf(getReturnType())) { throw new IllegalArgumentException( "Invokable is known to return " + getReturnType() + ", not " + returnType); } @SuppressWarnings("unchecked") // guarded by previous check Invokable specialized = (Invokable) this; return specialized; } @SuppressWarnings("unchecked") // The declaring class is T's raw class, or one of its supertypes. @Override public final Class getDeclaringClass() { return (Class) super.getDeclaringClass(); } /** Returns the type of {@code T}. */ // Overridden in TypeToken#method() and TypeToken#constructor() @SuppressWarnings("unchecked") // The declaring class is T. @Override public TypeToken getOwnerType() { return (TypeToken) TypeToken.of(getDeclaringClass()); } abstract Object invokeInternal(@Nullable Object receiver, Object[] args) throws InvocationTargetException, IllegalAccessException; abstract Type[] getGenericParameterTypes(); /** This should never return a type that's not a subtype of Throwable. */ abstract Type[] getGenericExceptionTypes(); abstract Annotation[][] getParameterAnnotations(); abstract Type getGenericReturnType(); static class MethodInvokable extends Invokable { final Method method; MethodInvokable(Method method) { super(method); this.method = method; } @Override final Object invokeInternal(@Nullable Object receiver, Object[] args) throws InvocationTargetException, IllegalAccessException { return method.invoke(receiver, args); } @Override Type getGenericReturnType() { return method.getGenericReturnType(); } @Override Type[] getGenericParameterTypes() { return method.getGenericParameterTypes(); } @Override Type[] getGenericExceptionTypes() { return method.getGenericExceptionTypes(); } @Override final Annotation[][] getParameterAnnotations() { return method.getParameterAnnotations(); } @Override public final TypeVariable[] getTypeParameters() { return method.getTypeParameters(); } @Override public final boolean isOverridable() { return !(isFinal() || isPrivate() || isStatic() || Modifier.isFinal(getDeclaringClass().getModifiers())); } @Override public final boolean isVarArgs() { return method.isVarArgs(); } } static class ConstructorInvokable extends Invokable { final Constructor constructor; ConstructorInvokable(Constructor constructor) { super(constructor); this.constructor = constructor; } @Override final Object invokeInternal(@Nullable Object receiver, Object[] args) throws InvocationTargetException, IllegalAccessException { try { return constructor.newInstance(args); } catch (InstantiationException e) { throw new RuntimeException(constructor + " failed.", e); } } /** * If the class is parameterized, such as {@link java.util.ArrayList ArrayList}, this returns * {@code ArrayList}. */ @Override Type getGenericReturnType() { Class declaringClass = getDeclaringClass(); TypeVariable[] typeParams = declaringClass.getTypeParameters(); if (typeParams.length > 0) { return Types.newParameterizedType(declaringClass, typeParams); } else { return declaringClass; } } @Override Type[] getGenericParameterTypes() { Type[] types = constructor.getGenericParameterTypes(); if (types.length > 0 && mayNeedHiddenThis()) { Class[] rawParamTypes = constructor.getParameterTypes(); if (types.length == rawParamTypes.length && rawParamTypes[0] == getDeclaringClass().getEnclosingClass()) { // first parameter is the hidden 'this' return Arrays.copyOfRange(types, 1, types.length); } } return types; } @Override Type[] getGenericExceptionTypes() { return constructor.getGenericExceptionTypes(); } @Override final Annotation[][] getParameterAnnotations() { return constructor.getParameterAnnotations(); } /** * {@inheritDoc} * * {@code []} will be returned for ArrayList's constructor. When both the class and the * constructor have type parameters, the class parameters are prepended before those of the * constructor's. This is an arbitrary rule since no existing language spec mandates one way or * the other. From the declaration syntax, the class type parameter appears first, but the call * syntax may show up in opposite order such as {@code new Foo()}. */ @Override public final TypeVariable[] getTypeParameters() { TypeVariable[] declaredByClass = getDeclaringClass().getTypeParameters(); TypeVariable[] declaredByConstructor = constructor.getTypeParameters(); TypeVariable[] result = new TypeVariable[declaredByClass.length + declaredByConstructor.length]; System.arraycopy(declaredByClass, 0, result, 0, declaredByClass.length); System.arraycopy( declaredByConstructor, 0, result, declaredByClass.length, declaredByConstructor.length); return result; } @Override public final boolean isOverridable() { return false; } @Override public final boolean isVarArgs() { return constructor.isVarArgs(); } private boolean mayNeedHiddenThis() { Class declaringClass = constructor.getDeclaringClass(); if (declaringClass.getEnclosingConstructor() != null) { // Enclosed in a constructor, needs hidden this return true; } Method enclosingMethod = declaringClass.getEnclosingMethod(); if (enclosingMethod != null) { // Enclosed in a method, if it's not static, must need hidden this. return !Modifier.isStatic(enclosingMethod.getModifiers()); } else { // Strictly, this doesn't necessarily indicate a hidden 'this' in the case of // static initializer. But there seems no way to tell in that case. :( // This may cause issues when an anonymous class is created inside a static initializer, // and the class's constructor's first parameter happens to be the enclosing class. // In such case, we may mistakenly think that the class is within a non-static context // and the first parameter is the hidden 'this'. return declaringClass.getEnclosingClass() != null && !Modifier.isStatic(declaringClass.getModifiers()); } } } }




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