/*
* JBoss, Home of Professional Open Source
* Copyright 2008, Red Hat, Inc., and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* 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.jboss.weld.util.bytecode;
import java.util.List;
import org.jboss.classfilewriter.AccessFlag;
import org.jboss.classfilewriter.ClassFile;
import org.jboss.classfilewriter.ClassMethod;
import org.jboss.classfilewriter.DuplicateMemberException;
import org.jboss.classfilewriter.code.CodeAttribute;
import org.jboss.weld.bean.proxy.ProxyFactory;
/**
* Utility class for working with constructors in the low level javassist API
*
* @author Stuart Douglas
*/
public class ConstructorUtils {
private ConstructorUtils() {
}
/**
* adds a constructor that calls super()
*/
public static void addDefaultConstructor(ClassFile file, List<DeferredBytecode> initialValueBytecode, final boolean useUnsafeInstantiators) {
addConstructor(DescriptorUtils.VOID_CLASS_DESCRIPTOR, new String[0], new String[0], file, initialValueBytecode, useUnsafeInstantiators);
}
/**
* Adds a constructor that delegates to a super constructor with the same
* descriptor. The bytecode in initialValueBytecode will be executed at the
* start of the constructor and can be used to initialize fields to a default
* value. As the object is not properly constructed at this point this
* bytecode may not reference this (i.e. the variable at location 0)
*
* @param returnType the constructor descriptor
* @param exceptions any exceptions that are thrown
* @param file the classfile to add the constructor to
* @param initialValueBytecode bytecode that can be used to set initial values
*/
public static void addConstructor(String returnType, String[] params, String[] exceptions, ClassFile file, List<DeferredBytecode> initialValueBytecode, final boolean useUnsafeInstantiators) {
try {
final String initMethodName = "<init>";
final ClassMethod ctor = file.addMethod(AccessFlag.PUBLIC, initMethodName, returnType, params);
ctor.addCheckedExceptions(exceptions);
final CodeAttribute b = ctor.getCodeAttribute();
for(final DeferredBytecode iv : initialValueBytecode) {
iv.apply(b);
}
// we need to generate a constructor with a single invokespecial call
// to the super constructor
// to do this we need to push all the arguments on the stack first
// local variables is the number of parameters +1 for this
// if some of the parameters are wide this may go up.
b.aload(0);
b.loadMethodParameters();
// now we have the parameters on the stack
b.invokespecial(file.getSuperclass(), initMethodName, DescriptorUtils.getMethodDescriptor(params, returnType));
if(!useUnsafeInstantiators) {
// now set constructed to true
b.aload(0);
b.iconst(1);
b.putfield(file.getName(), ProxyFactory.CONSTRUCTED_FLAG_NAME, DescriptorUtils.BOOLEAN_CLASS_DESCRIPTOR);
}
b.returnInstruction();
} catch (DuplicateMemberException e) {
throw new RuntimeException(e);
}
}
}