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An unofficial backport of the JDK Classfile API to Java 17
/*
* Copyright (c) 2022, 2023, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package io.github.dmlloyd.classfile;
import java.io.InputStream;
import java.lang.constant.ClassDesc;
import java.lang.invoke.MethodHandles;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Function;
import java.util.function.Supplier;
import io.github.dmlloyd.classfile.impl.ClassHierarchyImpl;
import io.github.dmlloyd.classfile.impl.ClassHierarchyImpl.ClassLoadingClassHierarchyResolver;
import io.github.dmlloyd.classfile.impl.ClassHierarchyImpl.StaticClassHierarchyResolver;
import io.github.dmlloyd.classfile.impl.Util;
import static java.lang.constant.ConstantDescs.CD_Object;
import io.github.dmlloyd.classfile.extras.PreviewFeature;
/**
* Provides class hierarchy information for generating correct stack maps
* during code building.
*
* @since 22
*/
@PreviewFeature(feature = PreviewFeature.Feature.CLASSFILE_API)
@FunctionalInterface
public interface ClassHierarchyResolver {
/**
* {@return the default instance of {@linkplain ClassHierarchyResolver} that
* gets {@link ClassHierarchyInfo} from system class loader with reflection}
*/
static ClassHierarchyResolver defaultResolver() {
return ClassHierarchyImpl.DEFAULT_RESOLVER;
}
/**
* {@return the {@link ClassHierarchyInfo} for a given class name, or null
* if the name is unknown to the resolver}
* @param classDesc descriptor of the class
* @throws IllegalArgumentException if a class shouldn't be queried for hierarchy
*/
ClassHierarchyInfo getClassInfo(ClassDesc classDesc);
/**
* Information about a resolved class.
*
* @since 22
*/
@PreviewFeature(feature = PreviewFeature.Feature.CLASSFILE_API)
sealed interface ClassHierarchyInfo permits ClassHierarchyImpl.ClassHierarchyInfoImpl {
/**
* Indicates that a class is a declared class, with the specific given super class.
*
* @param superClass descriptor of the super class, may be {@code null}
* @return the info indicating the super class
*/
static ClassHierarchyInfo ofClass(ClassDesc superClass) {
return new ClassHierarchyImpl.ClassHierarchyInfoImpl(superClass, false);
}
/**
* Indicates that a class is an interface.
*
* @return the info indicating an interface
*/
static ClassHierarchyInfo ofInterface() {
return new ClassHierarchyImpl.ClassHierarchyInfoImpl(CD_Object, true);
}
}
/**
* Chains this {@linkplain ClassHierarchyResolver} with another to be
* consulted if this resolver does not know about the specified class.
*
* @param other the other resolver
* @return the chained resolver
*
* @implSpec The default implementation returns resolver implemented to ask
* other resolver in cases where this resolver returns {@code null}.
*/
default ClassHierarchyResolver orElse(ClassHierarchyResolver other) {
return new ClassHierarchyResolver() {
@Override
public ClassHierarchyInfo getClassInfo(ClassDesc classDesc) {
var chi = ClassHierarchyResolver.this.getClassInfo(classDesc);
if (chi == null)
return other.getClassInfo(classDesc);
return chi;
}
};
}
/**
* Returns a ClassHierarchyResolver that caches class hierarchy information from this
* resolver. The returned resolver will not update if delegate resolver returns differently.
* The thread safety of the returned resolver depends on the thread safety of the map
* returned by the {@code cacheFactory}.
*
* @param cacheFactory the factory for the cache
* @return the ClassHierarchyResolver with caching
*
* @implSpec The default implementation returns resolver holding an instance
* of the cache map provided by the {@code cacheFactory}. It asks
* the cache map always first and fills the cache map with all
* resolved and also unresolved class info. The cache map may refuse
* {@code null} keys and values.
*/
default ClassHierarchyResolver cached(Supplier> cacheFactory) {
return new ClassHierarchyImpl.CachedClassHierarchyResolver(this, cacheFactory.get());
}
/**
* Returns a ClassHierarchyResolver that caches class hierarchy information from this
* resolver. The returned resolver will not update if delegate resolver returns differently.
* The returned resolver is not thread-safe.
* {@snippet file="PackageSnippets.java" region="lookup-class-hierarchy-resolver"}
*
* @return the ClassHierarchyResolver
*
* @implSpec The default implementation calls {@link #cached(Supplier)} with
* {@link HashMap} supplier as {@code cacheFactory}.
*/
default ClassHierarchyResolver cached() {
record Factory() implements Supplier> {
// uses a record as we cannot declare a local class static
static final Factory INSTANCE = new Factory();
@Override
public Map get() {
return new HashMap<>();
}
}
return cached(Factory.INSTANCE);
}
/**
* Returns a {@linkplain ClassHierarchyResolver} that extracts class hierarchy
* information from classfiles located by a mapping function. The mapping function
* should return null if it cannot provide a mapping for a classfile. Any IOException
* from the provided input stream is rethrown as an UncheckedIOException.
*
* @param classStreamResolver maps class descriptors to classfile input streams
* @return the {@linkplain ClassHierarchyResolver}
*/
static ClassHierarchyResolver ofResourceParsing(Function classStreamResolver) {
return new ClassHierarchyImpl.ResourceParsingClassHierarchyResolver(classStreamResolver);
}
/**
* Returns a {@linkplain ClassHierarchyResolver} that extracts class hierarchy
* information from classfiles located by a class loader.
*
* @param loader the class loader, to find class files
* @return the {@linkplain ClassHierarchyResolver}
*/
static ClassHierarchyResolver ofResourceParsing(ClassLoader loader) {
return ofResourceParsing(new Function<>() {
@Override
public InputStream apply(ClassDesc classDesc) {
return loader.getResourceAsStream(Util.toInternalName(classDesc) + ".class");
}
});
}
/**
* Returns a {@linkplain ClassHierarchyResolver} that extracts class hierarchy
* information from collections of class hierarchy metadata
*
* @param interfaces a collection of classes known to be interfaces
* @param classToSuperClass a map from classes to their super classes
* @return the {@linkplain ClassHierarchyResolver}
*/
static ClassHierarchyResolver of(Collection interfaces,
Map classToSuperClass) {
return new StaticClassHierarchyResolver(interfaces, classToSuperClass);
}
/**
* Returns a ClassHierarchyResolver that extracts class hierarchy information via
* the Reflection API with a {@linkplain ClassLoader}.
*
* @param loader the class loader
* @return the class hierarchy resolver
*/
static ClassHierarchyResolver ofClassLoading(ClassLoader loader) {
return new ClassLoadingClassHierarchyResolver(new Function<>() {
@Override
public Class apply(ClassDesc cd) {
try {
return Class.forName(Util.toBinaryName(cd), false, loader);
} catch (ClassNotFoundException ex) {
return null;
}
}
});
}
/**
* Returns a ClassHierarchyResolver that extracts class hierarchy information via
* the Reflection API with a {@linkplain MethodHandles.Lookup Lookup}. If the class
* resolved is inaccessible to the given lookup, it throws {@link
* IllegalArgumentException} instead of returning {@code null}.
*
* @param lookup the lookup, must be able to access classes to resolve
* @return the class hierarchy resolver
*/
static ClassHierarchyResolver ofClassLoading(MethodHandles.Lookup lookup) {
return new ClassLoadingClassHierarchyResolver(new Function<>() {
@Override
public Class apply(ClassDesc cd) {
try {
return (Class) cd.resolveConstantDesc(lookup);
} catch (IllegalAccessException ex) {
throw new IllegalArgumentException(ex);
} catch (ReflectiveOperationException ex) {
return null;
}
}
});
}
}