/*
* Copyright 2010 the original author or 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 org.gradle.groovy.scripts;
import groovy.lang.Script;
import org.gradle.util.ReflectionUtil;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import java.util.HashMap;
import java.util.Map;
public class AsmBackedEmptyScriptGenerator {
private static final Map<Class<?>, Class<?>> CACHED_CLASSES = new HashMap<Class<?>, Class<?>>();
<T extends Script> Class<? extends T> generate(Class<T> type) {
Class<?> subclass = CACHED_CLASSES.get(type);
if (subclass == null) {
subclass = generateEmptyScriptClass(type);
CACHED_CLASSES.put(type, subclass);
}
return subclass.asSubclass(type);
}
private <T extends Script> Class<? extends T> generateEmptyScriptClass(Class<T> type) {
ClassWriter visitor = new ClassWriter(ClassWriter.COMPUTE_MAXS);
String typeName = type.getName() + "_Decorated";
Type generatedType = Type.getType("L" + typeName.replaceAll("\\.", "/") + ";");
Type superclassType = Type.getType(type);
visitor.visit(Opcodes.V1_5, Opcodes.ACC_PUBLIC, generatedType.getInternalName(), null,
superclassType.getInternalName(), new String[0]);
// Constructor
String constructorDescriptor = Type.getMethodDescriptor(Type.VOID_TYPE, new Type[0]);
MethodVisitor methodVisitor = visitor.visitMethod(Opcodes.ACC_PUBLIC, "<init>", constructorDescriptor, null,
new String[0]);
methodVisitor.visitCode();
// super()
methodVisitor.visitVarInsn(Opcodes.ALOAD, 0);
methodVisitor.visitMethodInsn(Opcodes.INVOKESPECIAL, superclassType.getInternalName(), "<init>",
constructorDescriptor);
methodVisitor.visitInsn(Opcodes.RETURN);
methodVisitor.visitMaxs(0, 0);
methodVisitor.visitEnd();
// run() method
String runDesciptor = Type.getMethodDescriptor(Type.getType(Object.class), new Type[0]);
methodVisitor = visitor.visitMethod(Opcodes.ACC_PUBLIC, "run", runDesciptor, null, new String[0]);
methodVisitor.visitCode();
// return null
methodVisitor.visitInsn(Opcodes.ACONST_NULL);
methodVisitor.visitInsn(Opcodes.ARETURN);
methodVisitor.visitMaxs(0, 0);
methodVisitor.visitEnd();
visitor.visitEnd();
byte[] bytecode = visitor.toByteArray();
return (Class<T>) ReflectionUtil.invoke(type.getClassLoader(), "defineClass", new Object[]{
typeName, bytecode, 0, bytecode.length
});
}
}