/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.beam.sdk.util.common;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static java.util.Arrays.asList;
import com.google.common.base.Function;
import com.google.common.base.Joiner;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Queues;
import java.lang.annotation.Annotation;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.WildcardType;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Queue;
import java.util.ServiceLoader;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
/**
* Utilities for working with with {@link Class Classes} and {@link Method Methods}.
*/
public class ReflectHelpers {
private static final Joiner COMMA_SEPARATOR = Joiner.on(", ");
/** A {@link Function} that turns a method into a simple method signature. */
public static final Function<Method, String> METHOD_FORMATTER = new Function<Method, String>() {
@Override
public String apply(@Nonnull Method input) {
String parameterTypes = FluentIterable.from(asList(input.getParameterTypes()))
.transform(CLASS_SIMPLE_NAME)
.join(COMMA_SEPARATOR);
return String.format("%s(%s)",
input.getName(),
parameterTypes);
}
};
/** A {@link Function} that turns a method into the declaring class + method signature. */
public static final Function<Method, String> CLASS_AND_METHOD_FORMATTER =
new Function<Method, String>() {
@Override
public String apply(@Nonnull Method input) {
return String.format("%s#%s",
CLASS_NAME.apply(input.getDeclaringClass()),
METHOD_FORMATTER.apply(input));
}
};
/** A {@link Function} with returns the classes name. */
public static final Function<Class<?>, String> CLASS_NAME =
new Function<Class<?>, String>() {
@Override
public String apply(@Nonnull Class<?> input) {
return input.getName();
}
};
/** A {@link Function} with returns the classes name. */
public static final Function<Class<?>, String> CLASS_SIMPLE_NAME =
new Function<Class<?>, String>() {
@Override
public String apply(@Nonnull Class<?> input) {
return input.getSimpleName();
}
};
/**
* A {@link Function} that returns a concise string for a {@link Annotation}.
*/
public static final Function<Annotation, String> ANNOTATION_FORMATTER =
new Function<Annotation, String>() {
@Override
public String apply(@Nonnull Annotation annotation) {
String annotationName = annotation.annotationType().getName();
String annotationNameWithoutPackage =
annotationName.substring(annotationName.lastIndexOf('.') + 1).replace('$', '.');
String annotationToString = annotation.toString();
String values = annotationToString.substring(annotationToString.indexOf('('));
return String.format("%s%s", annotationNameWithoutPackage, values);
}
};
/** A {@link Function} that formats types. */
public static final Function<Type, String> TYPE_SIMPLE_DESCRIPTION =
new Function<Type, String>() {
@Override
@Nullable
public String apply(@Nonnull Type input) {
StringBuilder builder = new StringBuilder();
format(builder, input);
return builder.toString();
}
private void format(StringBuilder builder, Type t) {
if (t instanceof Class) {
formatClass(builder, (Class<?>) t);
} else if (t instanceof TypeVariable) {
formatTypeVariable(builder, (TypeVariable<?>) t);
} else if (t instanceof WildcardType) {
formatWildcardType(builder, (WildcardType) t);
} else if (t instanceof ParameterizedType) {
formatParameterizedType(builder, (ParameterizedType) t);
} else if (t instanceof GenericArrayType) {
formatGenericArrayType(builder, (GenericArrayType) t);
} else {
builder.append(t.toString());
}
}
private void formatClass(StringBuilder builder, Class<?> clazz) {
builder.append(clazz.getSimpleName());
}
private void formatTypeVariable(StringBuilder builder, TypeVariable<?> t) {
builder.append(t.getName());
}
private void formatWildcardType(StringBuilder builder, WildcardType t) {
builder.append("?");
for (Type lowerBound : t.getLowerBounds()) {
builder.append(" super ");
format(builder, lowerBound);
}
for (Type upperBound : t.getUpperBounds()) {
if (!Object.class.equals(upperBound)) {
builder.append(" extends ");
format(builder, upperBound);
}
}
}
private void formatParameterizedType(StringBuilder builder, ParameterizedType t) {
if (t.getOwnerType() != null) {
format(builder, t.getOwnerType());
builder.append('.');
}
format(builder, t.getRawType());
if (t.getActualTypeArguments().length > 0) {
builder.append('<');
COMMA_SEPARATOR.appendTo(builder,
FluentIterable.from(asList(t.getActualTypeArguments()))
.transform(TYPE_SIMPLE_DESCRIPTION));
builder.append('>');
}
}
private void formatGenericArrayType(StringBuilder builder, GenericArrayType t) {
format(builder, t.getGenericComponentType());
builder.append("[]");
}
};
/** A {@link Comparator} that uses the object's classes canonical name to compare them. */
public static class ObjectsClassComparator implements Comparator<Object> {
public static final ObjectsClassComparator INSTANCE = new ObjectsClassComparator();
@Override
public int compare(Object o1, Object o2) {
return o1.getClass().getCanonicalName().compareTo(o2.getClass().getCanonicalName());
}
}
/**
* Returns all the methods visible from the provided interfaces.
*
* @param interfaces The interfaces to use when searching for all their methods.
* @return An iterable of {@link Method}s which interfaces expose.
*/
public static Iterable<Method> getClosureOfMethodsOnInterfaces(
Iterable<? extends Class<?>> interfaces) {
return FluentIterable.from(interfaces).transformAndConcat(
new Function<Class<?>, Iterable<Method>>() {
@Override
public Iterable<Method> apply(@Nonnull Class<?> input) {
return getClosureOfMethodsOnInterface(input);
}
});
}
/**
* Returns all the methods visible from {@code iface}.
*
* @param iface The interface to use when searching for all its methods.
* @return An iterable of {@link Method}s which {@code iface} exposes.
*/
public static Iterable<Method> getClosureOfMethodsOnInterface(Class<?> iface) {
checkNotNull(iface);
checkArgument(iface.isInterface());
ImmutableSet.Builder<Method> builder = ImmutableSet.builder();
Queue<Class<?>> interfacesToProcess = Queues.newArrayDeque();
interfacesToProcess.add(iface);
while (!interfacesToProcess.isEmpty()) {
Class<?> current = interfacesToProcess.remove();
builder.add(current.getMethods());
interfacesToProcess.addAll(Arrays.asList(current.getInterfaces()));
}
return builder.build();
}
/**
* Finds the appropriate {@code ClassLoader} to be used by the
* {@link ServiceLoader#load} call, which by default would use the context
* {@code ClassLoader}, which can be null. The fallback is as follows: context
* ClassLoader, class ClassLoader and finaly the system ClassLoader.
*/
public static ClassLoader findClassLoader() {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
if (classLoader == null) {
classLoader = ReflectHelpers.class.getClassLoader();
}
if (classLoader == null) {
classLoader = ClassLoader.getSystemClassLoader();
}
return classLoader;
}
}