package com.fasterxml.jackson.module.afterburner.deser;
import static org.objectweb.asm.Opcodes.*;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.deser.ValueInstantiator;
import com.fasterxml.jackson.databind.deser.std.StdValueInstantiator;
import com.fasterxml.jackson.databind.introspect.AnnotatedWithParams;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Type;
import com.fasterxml.jackson.module.afterburner.util.DynamicPropertyAccessorBase;
import com.fasterxml.jackson.module.afterburner.util.MyClassLoader;
/**
* Helper class that tries to generate {@link ValueInstantiator} class
* that calls constructors and/or factory methods directly, instead
* of using Reflection.
*/
public class CreatorOptimizer
extends DynamicPropertyAccessorBase
{
protected final Class<?> _valueClass;
protected final MyClassLoader _classLoader;
protected final StdValueInstantiator _originalInstantiator;
public CreatorOptimizer(Class<?> valueClass, MyClassLoader classLoader,
StdValueInstantiator orig)
{
_valueClass = valueClass;
_classLoader = classLoader;
_originalInstantiator = orig;
}
public ValueInstantiator createOptimized()
{
/* [Issue#11]: Need to avoid optimizing if we use delegate- or
* property-based creators.
*/
if (_originalInstantiator.canCreateFromObjectWith()
|| _originalInstantiator.canCreateUsingDelegate()) {
return null;
}
// for now, only consider need to handle default creator
AnnotatedWithParams defaultCreator = _originalInstantiator.getDefaultCreator();
if (defaultCreator != null) {
AnnotatedElement elem = defaultCreator.getAnnotated();
if (elem instanceof Constructor<?>) {
return createSubclass((Constructor<?>) elem, null);
}
if (elem instanceof Method) {
Method m = (Method) elem;
if (Modifier.isStatic(m.getModifiers())) {
return createSubclass(null, m);
}
}
}
return null;
}
protected ValueInstantiator createSubclass(Constructor<?> ctor, Method factory)
{
MyClassLoader loader = (_classLoader == null) ?
new MyClassLoader(_valueClass.getClassLoader(), true) : _classLoader;
String srcName = _valueClass.getName() + "$Creator4JacksonDeserializer";
Class<?> impl = null;
try {
impl = loader.loadClass(srcName);
} catch (ClassNotFoundException e) { }
if (impl == null) {
byte[] bytecode = generateOptimized(srcName, ctor, factory);
impl = loader.loadAndResolve(srcName, bytecode);
}
ValueInstantiator inst;
try {
inst = (ValueInstantiator) impl.newInstance();
} catch (Exception e) {
throw new IllegalStateException("Failed to generate accessor class '"+srcName+"': "+e.getMessage(), e);
}
return inst;
}
protected byte[] generateOptimized(String srcName, Constructor<?> ctor, Method factory)
{
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
String superClass = internalClassName(OptimizedValueInstantiator.class.getName());
String generatedClass = internalClassName(srcName);
cw.visit(V1_5, ACC_PUBLIC + ACC_SUPER, generatedClass, null, superClass, null);
cw.visitSource(srcName + ".java", null);
// First: must define 2 constructors:
// (a) default constructor, for creating bogus instance (just calls default instance)
// (b) copy-constructor which takes StdValueInstantiator instance, passes to superclass
final String optimizedValueInstDesc = Type.getDescriptor(OptimizedValueInstantiator.class);
final String stdValueInstDesc = Type.getDescriptor(StdValueInstantiator.class);
// default (no-arg) constructor:
MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
mv.visitCode();
mv.visitVarInsn(ALOAD, 0);
mv.visitMethodInsn(INVOKESPECIAL, superClass, "<init>", "()V");
mv.visitInsn(RETURN);
mv.visitMaxs(0, 0);
mv.visitEnd();
// then single-arg constructor
mv = cw.visitMethod(ACC_PUBLIC, "<init>", "("+stdValueInstDesc+")V", null, null);
mv.visitCode();
mv.visitVarInsn(ALOAD, 0);
mv.visitVarInsn(ALOAD, 1);
mv.visitMethodInsn(INVOKESPECIAL, superClass, "<init>", "("+stdValueInstDesc+")V");
mv.visitInsn(RETURN);
mv.visitMaxs(0, 0);
mv.visitEnd();
// and then non-static factory method to use second constructor (implements base-class method)
// protected abstract OptimizedValueInstantiator with(StdValueInstantiator src);
mv = cw.visitMethod(ACC_PUBLIC, "with", "("
+stdValueInstDesc+")"+optimizedValueInstDesc, null, null);
mv.visitCode();
mv.visitTypeInsn(NEW, generatedClass);
mv.visitInsn(DUP);
mv.visitVarInsn(ALOAD, 1);
mv.visitMethodInsn(INVOKESPECIAL, generatedClass, "<init>", "("+stdValueInstDesc+")V");
mv.visitInsn(ARETURN);
mv.visitMaxs(0, 0);
mv.visitEnd();
// And then override: public Object createUsingDefault()
mv = cw.visitMethod(ACC_PUBLIC, "createUsingDefault", "(" +
Type.getDescriptor(DeserializationContext.class)+")Ljava/lang/Object;", null, null);
mv.visitCode();
if (ctor != null) {
addCreator(mv, ctor);
} else {
addCreator(mv, factory);
}
mv.visitInsn(ARETURN);
mv.visitMaxs(0, 0);
mv.visitEnd();
cw.visitEnd();
return cw.toByteArray();
}
protected void addCreator(MethodVisitor mv, Constructor<?> ctor)
{
String valueClassInternal = Type.getInternalName(ctor.getDeclaringClass());
mv.visitTypeInsn(NEW, valueClassInternal);
mv.visitInsn(DUP);
mv.visitMethodInsn(INVOKESPECIAL, valueClassInternal, "<init>", "()V");
}
protected void addCreator(MethodVisitor mv, Method factory)
{
Class<?> valueClass = factory.getReturnType();
mv.visitMethodInsn(INVOKESTATIC, Type.getInternalName(factory.getDeclaringClass()),
factory.getName(), "()"+Type.getDescriptor(valueClass));
}
}