net.bytebuddy.dynamic.scaffold.ClassWriterStrategy Maven / Gradle / Ivy
/*
* Copyright 2014 - Present Rafael Winterhalter
*
* 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 net.bytebuddy.dynamic.scaffold;
import net.bytebuddy.description.type.TypeDescription;
import net.bytebuddy.pool.TypePool;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
/**
* A class writer strategy is responsible for the creation of a {@link ClassWriter} when creating a type.
*/
public interface ClassWriterStrategy {
/**
* Resolves a class writer.
*
* @param flags The flags to set.
* @param typePool A type pool for locating types.
* @return The class writer to use.
*/
ClassWriter resolve(int flags, TypePool typePool);
/**
* Resolves a class writer.
*
* @param flags The flags to set.
* @param typePool A type pool for locating types.
* @param classReader The class reader from which the original class is read.
* @return The class writer to use.
*/
ClassWriter resolve(int flags, TypePool typePool, ClassReader classReader);
/**
* Default implementations of class writer strategies.
*/
enum Default implements ClassWriterStrategy {
/**
* A class writer strategy that retains the original class's constant pool if applicable.
*/
CONSTANT_POOL_RETAINING {
/** {@inheritDoc} */
public ClassWriter resolve(int flags, TypePool typePool, ClassReader classReader) {
return new FrameComputingClassWriter(classReader, flags, typePool);
}
},
/**
* A class writer strategy that discards the original class's constant pool if applicable.
*/
CONSTANT_POOL_DISCARDING {
/** {@inheritDoc} */
public ClassWriter resolve(int flags, TypePool typePool, ClassReader classReader) {
return resolve(flags, typePool);
}
};
/**
* {@inheritDoc}
*/
public ClassWriter resolve(int flags, TypePool typePool) {
return new FrameComputingClassWriter(flags, typePool);
}
}
/**
* A class writer that piggy-backs on Byte Buddy's {@link TypePool} to avoid class loading or look-up errors when redefining a class.
* This is not available when creating a new class where automatic frame computation is however not normally a requirement.
*/
class FrameComputingClassWriter extends ClassWriter {
/**
* The type pool to use for computing stack map frames, if required.
*/
private final TypePool typePool;
/**
* Creates a new frame computing class writer.
*
* @param flags The flags to be handed to the writer.
* @param typePool The type pool to use for computing stack map frames, if required.
*/
public FrameComputingClassWriter(int flags, TypePool typePool) {
super(flags);
this.typePool = typePool;
}
/**
* Creates a new frame computing class writer.
*
* @param classReader The class reader from which the original class is read.
* @param flags The flags to be handed to the writer.
* @param typePool The type pool to use for computing stack map frames, if required.
*/
public FrameComputingClassWriter(ClassReader classReader, int flags, TypePool typePool) {
super(classReader, flags);
this.typePool = typePool;
}
/**
* {@inheritDoc}
*/
protected String getCommonSuperClass(String leftTypeName, String rightTypeName) {
TypeDescription leftType = typePool.describe(leftTypeName.replace('/', '.')).resolve();
TypeDescription rightType = typePool.describe(rightTypeName.replace('/', '.')).resolve();
if (leftType.isAssignableFrom(rightType)) {
return leftType.getInternalName();
} else if (leftType.isAssignableTo(rightType)) {
return rightType.getInternalName();
} else if (leftType.isInterface() || rightType.isInterface()) {
return TypeDescription.ForLoadedType.of(Object.class).getInternalName();
} else {
do {
TypeDescription.Generic superClass = leftType.getSuperClass();
if (superClass == null) {
return TypeDescription.ForLoadedType.of(Object.class).getInternalName();
}
leftType = superClass.asErasure();
} while (!leftType.isAssignableFrom(rightType));
return leftType.getInternalName();
}
}
}
}