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Jackson (https://github.com/FasterXML/jackson) extension module
used to enhance performance using bytecode generation to replace use of Reflection for
field access and method calls
package com.fasterxml.jackson.module.afterburner.ser;
import java.lang.reflect.Method;
import java.util.*;
import org.objectweb.asm.*;
import static org.objectweb.asm.Opcodes.*;
import com.fasterxml.jackson.databind.introspect.AnnotatedField;
import com.fasterxml.jackson.databind.ser.BeanPropertyWriter;
import com.fasterxml.jackson.module.afterburner.util.ClassName;
import com.fasterxml.jackson.module.afterburner.util.DynamicPropertyAccessorBase;
import com.fasterxml.jackson.module.afterburner.util.MyClassLoader;
/**
* Simple collector used to keep track of properties for which code-generated
* accessors are needed.
*/
public class PropertyAccessorCollector
extends DynamicPropertyAccessorBase
{
private static final Type STRING_TYPE = Type.getType(String.class);
private static final Type OBJECT_TYPE = Type.getType(Object.class);
private final List _booleanGetters = new LinkedList();
private final List _intGetters = new LinkedList();
private final List _longGetters = new LinkedList();
private final List _stringGetters = new LinkedList();
private final List _objectGetters = new LinkedList();
private final List _booleanFields = new LinkedList();
private final List _intFields = new LinkedList();
private final List _longFields = new LinkedList();
private final List _stringFields = new LinkedList();
private final List _objectFields = new LinkedList();
private final Class beanClass;
private final String beanClassName;
public PropertyAccessorCollector(Class beanClass) {
this.beanClass = beanClass;
this.beanClassName = Type.getInternalName(beanClass);
}
/*
/**********************************************************
/* Methods for collecting properties
/**********************************************************
*/
public BooleanMethodPropertyWriter addBooleanGetter(BeanPropertyWriter bpw) {
return _add(_booleanGetters, new BooleanMethodPropertyWriter(bpw, null, _booleanGetters.size(), null));
}
public IntMethodPropertyWriter addIntGetter(BeanPropertyWriter bpw) {
return _add(_intGetters, new IntMethodPropertyWriter(bpw, null, _intGetters.size(), null));
}
public LongMethodPropertyWriter addLongGetter(BeanPropertyWriter bpw) {
return _add(_longGetters, new LongMethodPropertyWriter(bpw, null, _longGetters.size(), null));
}
public StringMethodPropertyWriter addStringGetter(BeanPropertyWriter bpw) {
return _add(_stringGetters, new StringMethodPropertyWriter(bpw, null, _stringGetters.size(), null));
}
public ObjectMethodPropertyWriter addObjectGetter(BeanPropertyWriter bpw) {
return _add(_objectGetters, new ObjectMethodPropertyWriter(bpw, null, _objectGetters.size(), null));
}
public BooleanFieldPropertyWriter addBooleanField(BeanPropertyWriter bpw) {
return _add(_booleanFields, new BooleanFieldPropertyWriter(bpw, null, _booleanFields.size(), null));
}
public IntFieldPropertyWriter addIntField(BeanPropertyWriter bpw) {
return _add(_intFields, new IntFieldPropertyWriter(bpw, null, _intFields.size(), null));
}
public LongFieldPropertyWriter addLongField(BeanPropertyWriter bpw) {
return _add(_longFields, new LongFieldPropertyWriter(bpw, null, _longFields.size(), null));
}
public StringFieldPropertyWriter addStringField(BeanPropertyWriter bpw) {
return _add(_stringFields, new StringFieldPropertyWriter(bpw, null, _stringFields.size(), null));
}
public ObjectFieldPropertyWriter addObjectField(BeanPropertyWriter bpw) {
return _add(_objectFields, new ObjectFieldPropertyWriter(bpw, null, _objectFields.size(), null));
}
/*
/**********************************************************
/* Code generation; high level
/**********************************************************
*/
public BeanPropertyAccessor findAccessor(MyClassLoader classLoader)
{
// if we weren't passed a class loader, we will base it on value type CL, try to use parent
if (classLoader == null) {
classLoader = new MyClassLoader(beanClass.getClassLoader(), true);
}
final ClassName baseName = ClassName.constructFor(beanClass, "$Access4JacksonSerializer");
Class accessorClass = generateAccessorClass(classLoader, baseName);
try {
return (BeanPropertyAccessor) accessorClass.newInstance();
} catch (Exception e) {
throw new IllegalStateException("Failed to generate accessor class '"+accessorClass.getName()+"': "+e.getMessage(), e);
}
}
public Class generateAccessorClass(MyClassLoader classLoader, ClassName baseName)
{
ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
String superClass = internalClassName(BeanPropertyAccessor.class.getName());
final String tmpClassName = baseName.getSlashedTemplate();
// muchos important: level at least 1.5 to get generics!!!
// 19-Apr-2017, tatu: For Jackson 2.9 SHOUD generate Java 7 bytecode. But...
cw.visit(V1_6, ACC_PUBLIC + ACC_SUPER + ACC_FINAL, tmpClassName,
null, superClass, null);
cw.visitSource(baseName.getSourceFilename(), null);
// add default (no-arg) constructor:
MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "", "()V", null, null);
mv.visitCode();
mv.visitVarInsn(ALOAD, 0);
mv.visitMethodInsn(INVOKESPECIAL, superClass, "", "()V", false);
mv.visitInsn(RETURN);
mv.visitMaxs(0, 0); // don't care (real values: 1,1)
mv.visitEnd();
// and then add various accessors; first field accessors:
if (!_intFields.isEmpty()) {
_addFields(cw, _intFields, "intField", Type.INT_TYPE, IRETURN);
}
if (!_longFields.isEmpty()) {
_addFields(cw, _longFields, "longField", Type.LONG_TYPE, LRETURN);
}
if (!_stringFields.isEmpty()) {
_addFields(cw, _stringFields, "stringField", STRING_TYPE, ARETURN);
}
if (!_objectFields.isEmpty()) {
_addFields(cw, _objectFields, "objectField", OBJECT_TYPE, ARETURN);
}
if (!_booleanFields.isEmpty()) {
// booleans treated as ints 0 (false) and 1 (true)
_addFields(cw, _booleanFields, "booleanField", Type.BOOLEAN_TYPE, IRETURN);
}
// and then method accessors:
if (!_intGetters.isEmpty()) {
_addGetters(cw, _intGetters, "intGetter", Type.INT_TYPE, IRETURN);
}
if (!_longGetters.isEmpty()) {
_addGetters(cw, _longGetters, "longGetter", Type.LONG_TYPE, LRETURN);
}
if (!_stringGetters.isEmpty()) {
_addGetters(cw, _stringGetters, "stringGetter", STRING_TYPE, ARETURN);
}
if (!_objectGetters.isEmpty()) {
_addGetters(cw, _objectGetters, "objectGetter", OBJECT_TYPE, ARETURN);
}
if (!_booleanGetters.isEmpty()) {
_addGetters(cw, _booleanGetters, "booleanGetter", Type.BOOLEAN_TYPE, IRETURN);
}
cw.visitEnd();
byte[] bytecode = cw.toByteArray();
baseName.assignChecksum(bytecode);
// Did we already generate this?
try {
return classLoader.loadClass(baseName.getDottedName());
} catch (ClassNotFoundException e) { }
// if not, load and resolve:
return classLoader.loadAndResolve(baseName, bytecode);
}
/*
/**********************************************************
/* Code generation; method-based getters
/**********************************************************
*/
private > void _addGetters(ClassWriter cw, List props,
String methodName, Type returnType, int returnOpcode)
{
MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, methodName, "(Ljava/lang/Object;I)"+returnType, /*generic sig*/null, null);
mv.visitCode();
// first: cast bean to proper type
mv.visitVarInsn(ALOAD, 1);
mv.visitTypeInsn(CHECKCAST, beanClassName);
mv.visitVarInsn(ASTORE, 3);
// Ok; minor optimization, 3 or fewer accessors, just do IFs; over that, use switch
switch (props.size()) {
case 1:
_addSingleGetter(mv, props.get(0), returnOpcode);
break;
case 2:
case 3:
_addGettersUsingIf(mv, props, returnOpcode);
break;
default:
_addGettersUsingSwitch(mv, props, returnOpcode);
}
// and if no match, generate exception:
generateException(mv, beanClassName, props.size());
mv.visitMaxs(0, 0); // don't care (real values: 1,1)
mv.visitEnd();
}
/*
/**********************************************************
/* Code generation; field-based getters
/**********************************************************
*/
private > void _addFields(ClassWriter cw, List props,
String methodName, Type returnType, int returnOpcode)
{
MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, methodName, "(Ljava/lang/Object;I)"+returnType, /*generic sig*/null, null);
mv.visitCode();
// first: cast bean to proper type
mv.visitVarInsn(ALOAD, 1);
mv.visitTypeInsn(CHECKCAST, beanClassName);
mv.visitVarInsn(ASTORE, 3);
// Ok; minor optimization, 3 or fewer fields, just do IFs; over that, use switch
switch (props.size()) {
case 1:
_addSingleField(mv, props.get(0), returnOpcode);
break;
case 2:
case 3:
_addFieldsUsingIf(mv, props, returnOpcode);
break;
default:
_addFieldsUsingSwitch(mv, props, returnOpcode);
}
// and if no match, generate exception:
generateException(mv, beanClassName, props.size());
mv.visitMaxs(0, 0); // don't care (real values: 1,1)
mv.visitEnd();
}
/*
/**********************************************************
/* Helper methods, method accessor creation
/**********************************************************
*/
private void _addSingleGetter(MethodVisitor mv,
OptimizedBeanPropertyWriter prop, int returnOpcode)
{
mv.visitVarInsn(ILOAD, 2); // load second arg (index)
mv.visitVarInsn(ALOAD, 3); // load local for cast bean
int invokeInsn = beanClass.isInterface() ? INVOKEINTERFACE : INVOKEVIRTUAL;
Method method = (Method) (prop.getMember().getMember());
mv.visitMethodInsn(invokeInsn, beanClassName, method.getName(),
Type.getMethodDescriptor(method), beanClass.isInterface());
mv.visitInsn(returnOpcode);
}
private > void _addGettersUsingIf(MethodVisitor mv,
List props, int returnOpcode)
{
mv.visitVarInsn(ILOAD, 2); // load second arg (index)
Label next = new Label();
// first: check if 'index == 0'
mv.visitJumpInsn(IFNE, next); // "if not zero, goto L (skip stuff)"
// call first getter:
mv.visitVarInsn(ALOAD, 3); // load local for cast bean
int invokeInsn = beanClass.isInterface() ? INVOKEINTERFACE : INVOKEVIRTUAL;
Method method = (Method) (props.get(0).getMember().getMember());
mv.visitMethodInsn(invokeInsn, beanClassName, method.getName(),
Type.getMethodDescriptor(method), beanClass.isInterface());
mv.visitInsn(returnOpcode);
// And from this point on, loop a bit
for (int i = 1, end = props.size()-1; i <= end; ++i) {
mv.visitLabel(next);
// No need to check index for the last one
if (i < end) {
next = new Label();
mv.visitVarInsn(ILOAD, 2); // load second arg (index)
mv.visitInsn(ALL_INT_CONSTS[i]);
mv.visitJumpInsn(IF_ICMPNE, next);
}
mv.visitVarInsn(ALOAD, 3); // load bean
method = (Method) (props.get(i).getMember().getMember());
mv.visitMethodInsn(invokeInsn, beanClassName, method.getName(),
Type.getMethodDescriptor(method), beanClass.isInterface());
mv.visitInsn(returnOpcode);
}
}
private > void _addGettersUsingSwitch(MethodVisitor mv,
List props, int returnOpcode)
{
mv.visitVarInsn(ILOAD, 2); // load second arg (index)
Label[] labels = new Label[props.size()];
for (int i = 0, len = labels.length; i < len; ++i) {
labels[i] = new Label();
}
Label defaultLabel = new Label();
mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);
int invokeInsn = beanClass.isInterface() ? INVOKEINTERFACE : INVOKEVIRTUAL;
for (int i = 0, len = labels.length; i < len; ++i) {
mv.visitLabel(labels[i]);
mv.visitVarInsn(ALOAD, 3); // load bean
Method method = (Method) (props.get(i).getMember().getMember());
mv.visitMethodInsn(invokeInsn, beanClassName, method.getName(),
Type.getMethodDescriptor(method), beanClass.isInterface());
mv.visitInsn(returnOpcode);
}
mv.visitLabel(defaultLabel);
}
private void _addSingleField(MethodVisitor mv, OptimizedBeanPropertyWriter prop, int returnOpcode)
{
mv.visitVarInsn(ILOAD, 2); // load second arg (index)
mv.visitVarInsn(ALOAD, 3); // load local for cast bean
AnnotatedField field = (AnnotatedField) prop.getMember();
mv.visitFieldInsn(GETFIELD, beanClassName, field.getName(), Type.getDescriptor(field.getRawType()));
mv.visitInsn(returnOpcode);
}
private > void _addFieldsUsingIf(MethodVisitor mv,
List props, int returnOpcode)
{
mv.visitVarInsn(ILOAD, 2); // load second arg (index)
Label next = new Label();
// first: check if 'index == 0'
mv.visitJumpInsn(IFNE, next); // "if not zero, goto L (skip stuff)"
// first field accessor
mv.visitVarInsn(ALOAD, 3); // load local for cast bean
AnnotatedField field = (AnnotatedField) props.get(0).getMember();
mv.visitFieldInsn(GETFIELD, beanClassName, field.getName(), Type.getDescriptor(field.getRawType()));
mv.visitInsn(returnOpcode);
// And from this point on, loop a bit
for (int i = 1, end = props.size()-1; i <= end; ++i) {
mv.visitLabel(next);
// No need to check index for the last one
if (i < end) {
next = new Label();
mv.visitVarInsn(ILOAD, 2); // load second arg (index)
mv.visitInsn(ALL_INT_CONSTS[i]);
mv.visitJumpInsn(IF_ICMPNE, next);
}
mv.visitVarInsn(ALOAD, 3); // load bean
field = (AnnotatedField) props.get(i).getMember();
mv.visitFieldInsn(GETFIELD, beanClassName, field.getName(), Type.getDescriptor(field.getRawType()));
mv.visitInsn(returnOpcode);
}
}
private > void _addFieldsUsingSwitch(MethodVisitor mv,
List props, int returnOpcode)
{
mv.visitVarInsn(ILOAD, 2); // load second arg (index)
Label[] labels = new Label[props.size()];
for (int i = 0, len = labels.length; i < len; ++i) {
labels[i] = new Label();
}
Label defaultLabel = new Label();
mv.visitTableSwitchInsn(0, labels.length - 1, defaultLabel, labels);
for (int i = 0, len = labels.length; i < len; ++i) {
mv.visitLabel(labels[i]);
mv.visitVarInsn(ALOAD, 3); // load bean
AnnotatedField field = (AnnotatedField) props.get(i).getMember();
mv.visitFieldInsn(GETFIELD, beanClassName, field.getName(), Type.getDescriptor(field.getRawType()));
mv.visitInsn(returnOpcode);
}
mv.visitLabel(defaultLabel);
}
}