/*
* 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 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.
*
* <p>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:
*
* <pre> {@code
* Method getMethod = List.class.getMethod("get", int.class);
* Invokable<List<String>, ?> invokable = new TypeToken<List<String>>() {}.method(getMethod);
* assertEquals(TypeToken.of(String.class), invokable.getReturnType()); // Not Object.class!
* assertEquals(new TypeToken<List<String>>() {}, invokable.getOwnerType());}</pre>
*
* @param <T> the type that owns this method or constructor.
* @param <R> 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<T, R> extends Element implements GenericDeclaration {
<M extends AccessibleObject & Member> Invokable(M member) {
super(member);
}
/** Returns {@link Invokable} of {@code method}. */
public static Invokable<?, Object> from(Method method) {
return new MethodInvokable<Object>(method);
}
/** Returns {@link Invokable} of {@code constructor}. */
public static <T> Invokable<T, T> from(Constructor<T> constructor) {
return new ConstructorInvokable<T>(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")
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<? extends R> getReturnType() {
return (TypeToken<? extends R>) 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<Parameter> getParameters() {
Type[] parameterTypes = getGenericParameterTypes();
Annotation[][] annotations = getParameterAnnotations();
ImmutableList.Builder<Parameter> 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<TypeToken<? extends Throwable>> getExceptionTypes() {
ImmutableList.Builder<TypeToken<? extends Throwable>> builder = ImmutableList.builder();
for (Type type : getGenericExceptionTypes()) {
// getGenericExceptionTypes() will never return a type that's not exception
@SuppressWarnings("unchecked")
TypeToken<? extends Throwable> exceptionType = (TypeToken<? extends Throwable>)
TypeToken.of(type);
builder.add(exceptionType);
}
return builder.build();
}
/**
* Explicitly specifies the return type of this {@code Invokable}. For example:
* <pre> {@code
* Method factoryMethod = Person.class.getMethod("create");
* Invokable<?, Person> factory = Invokable.of(getNameMethod).returning(Person.class);}</pre>
*/
public final <R1 extends R> Invokable<T, R1> returning(Class<R1> returnType) {
return returning(TypeToken.of(returnType));
}
/** Explicitly specifies the return type of this {@code Invokable}. */
public final <R1 extends R> Invokable<T, R1> returning(TypeToken<R1> returnType) {
if (!returnType.isAssignableFrom(getReturnType())) {
throw new IllegalArgumentException(
"Invokable is known to return " + getReturnType() + ", not " + returnType);
}
@SuppressWarnings("unchecked") // guarded by previous check
Invokable<T, R1> specialized = (Invokable<T, R1>) this;
return specialized;
}
@SuppressWarnings("unchecked") // The declaring class is T's raw class, or one of its supertypes.
@Override public final Class<? super T> getDeclaringClass() {
return (Class<? super T>) 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<T> getOwnerType() {
return (TypeToken<T>) 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<T> extends Invokable<T, Object> {
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<T> extends Invokable<T, T> {
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 ArrayList, this returns ArrayList<E>. */
@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 [<E>]} 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 <A>Foo<B>()}.
*/
@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());
}
}
}
}