|
|
Java example source code file (Invokable.java)
This example Java source code file (Invokable.java) is included in the alvinalexander.com
"Java Source Code
Warehouse" project. The intent of this project is to help you "Learn
Java by Example" TM.
Learn more about this Java project at its project page.
The Invokable.java Java example source code
/*
* 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.
*
* <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 invokable = new TypeToken>() {}.method(getMethod);
* assertEquals(TypeToken.of(String.class), invokable.getReturnType()); // Not Object.class!
* assertEquals(new TypeToken<List() {}, invokable.getOwnerType());}
*
* @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 from(Constructor 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")
@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<? 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 getExceptionTypes() {
ImmutableList.Builder<TypeToken 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);}
*/
public final <R1 extends R> Invokable returning(Class returnType) {
return returning(TypeToken.of(returnType));
}
/** Explicitly specifies the return type of this {@code Invokable}. */
public final <R1 extends R> 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<T, R1> specialized = (Invokable) 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 {
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 {
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()}.
*/
@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());
}
}
}
}
Other Java examples (source code examples)
Here is a short list of links related to this Java Invokable.java source code file:
|
The search page
Other Java source code examples at this package level
Click here to learn more about this project
