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General data-binding functionality for Jackson: works on core streaming API
package com.fasterxml.jackson.databind.jdk14;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.List;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonCreator.Mode;
import com.fasterxml.jackson.databind.AnnotationIntrospector;
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.introspect.AnnotatedConstructor;
import com.fasterxml.jackson.databind.util.ClassUtil;
/**
* Helper class to support some of JDK 14 (and later) features
* without Jackson itself being run on (or even built with) Java 14.
* In particular allows better support of {@code java.lang.Record}
* types (see JEP 359).
*
* @since 2.12
*/
public class JDK14Util
{
public static String[] getRecordFieldNames(Class recordType) {
return RecordAccessor.instance().getRecordFieldNames(recordType);
}
public static AnnotatedConstructor findRecordConstructor(DeserializationContext ctxt,
BeanDescription beanDesc, List names) {
return new CreatorLocator(ctxt, beanDesc)
.locate(names);
}
static class RecordAccessor {
private final Method RECORD_GET_RECORD_COMPONENTS;
private final Method RECORD_COMPONENT_GET_NAME;
private final Method RECORD_COMPONENT_GET_TYPE;
private final static RecordAccessor INSTANCE;
private final static RuntimeException PROBLEM;
static {
RuntimeException prob = null;
RecordAccessor inst = null;
try {
inst = new RecordAccessor();
} catch (RuntimeException e) {
prob = e;
}
INSTANCE = inst;
PROBLEM = prob;
}
private RecordAccessor() throws RuntimeException {
try {
RECORD_GET_RECORD_COMPONENTS = Class.class.getMethod("getRecordComponents");
Class c = Class.forName("java.lang.reflect.RecordComponent");
RECORD_COMPONENT_GET_NAME = c.getMethod("getName");
RECORD_COMPONENT_GET_TYPE = c.getMethod("getType");
} catch (Exception e) {
throw new RuntimeException(String.format(
"Failed to access Methods needed to support `java.lang.Record`: (%s) %s",
e.getClass().getName(), e.getMessage()), e);
}
}
public static RecordAccessor instance() {
if (PROBLEM != null) {
throw PROBLEM;
}
return INSTANCE;
}
public String[] getRecordFieldNames(Class recordType) throws IllegalArgumentException
{
final Object[] components = recordComponents(recordType);
final String[] names = new String[components.length];
for (int i = 0; i < components.length; i++) {
try {
names[i] = (String) RECORD_COMPONENT_GET_NAME.invoke(components[i]);
} catch (Exception e) {
throw new IllegalArgumentException(String.format(
"Failed to access name of field #%d (of %d) of Record type %s",
i, components.length, ClassUtil.nameOf(recordType)), e);
}
}
return names;
}
public RawTypeName[] getRecordFields(Class recordType) throws IllegalArgumentException
{
final Object[] components = recordComponents(recordType);
final RawTypeName[] results = new RawTypeName[components.length];
for (int i = 0; i < components.length; i++) {
String name;
try {
name = (String) RECORD_COMPONENT_GET_NAME.invoke(components[i]);
} catch (Exception e) {
throw new IllegalArgumentException(String.format(
"Failed to access name of field #%d (of %d) of Record type %s",
i, components.length, ClassUtil.nameOf(recordType)), e);
}
Class type;
try {
type = (Class) RECORD_COMPONENT_GET_TYPE.invoke(components[i]);
} catch (Exception e) {
throw new IllegalArgumentException(String.format(
"Failed to access type of field #%d (of %d) of Record type %s",
i, components.length, ClassUtil.nameOf(recordType)), e);
}
results[i] = new RawTypeName(type, name);
}
return results;
}
protected Object[] recordComponents(Class recordType) throws IllegalArgumentException
{
try {
return (Object[]) RECORD_GET_RECORD_COMPONENTS.invoke(recordType);
} catch (Exception e) {
throw new IllegalArgumentException("Failed to access RecordComponents of type "
+ClassUtil.nameOf(recordType));
}
}
}
static class RawTypeName {
public final Class rawType;
public final String name;
public RawTypeName(Class rt, String n) {
rawType = rt;
name = n;
}
}
static class CreatorLocator {
protected final BeanDescription _beanDesc;
protected final DeserializationConfig _config;
protected final AnnotationIntrospector _intr;
protected final List _constructors;
protected final AnnotatedConstructor _primaryConstructor;
protected final RawTypeName[] _recordFields;
CreatorLocator(DeserializationContext ctxt, BeanDescription beanDesc)
{
_beanDesc = beanDesc;
_intr = ctxt.getAnnotationIntrospector();
_config = ctxt.getConfig();
_recordFields = RecordAccessor.instance().getRecordFields(beanDesc.getBeanClass());
final int argCount = _recordFields.length;
// And then locate the canonical constructor; must be found, if not, fail
// altogether (so we can figure out what went wrong)
AnnotatedConstructor primary = null;
// One special case: empty Records, empty constructor is separate case
if (argCount == 0) {
primary = beanDesc.findDefaultConstructor();
_constructors = Collections.singletonList(primary);
} else {
_constructors = beanDesc.getConstructors();
main_loop:
for (AnnotatedConstructor ctor : _constructors) {
if (ctor.getParameterCount() != argCount) {
continue;
}
for (int i = 0; i < argCount; ++i) {
if (!ctor.getRawParameterType(i).equals(_recordFields[i].rawType)) {
continue main_loop;
}
}
primary = ctor;
break;
}
}
if (primary == null) {
throw new IllegalArgumentException("Failed to find the canonical Record constructor of type "
+ClassUtil.getTypeDescription(_beanDesc.getType()));
}
_primaryConstructor = primary;
}
public AnnotatedConstructor locate(List names)
{
// First things first: ensure that either there are no explicit marked constructors
// or that there is just one and it is the canonical one and it is not
// declared as "delegating" constructor
for (AnnotatedConstructor ctor : _constructors) {
JsonCreator.Mode creatorMode = _intr.findCreatorAnnotation(_config, ctor);
if ((null == creatorMode) || (Mode.DISABLED == creatorMode)) {
continue;
}
// If there's a delegating Creator let caller figure out
if (Mode.DELEGATING == creatorMode) {
return null;
}
if (ctor != _primaryConstructor) {
return null;
}
}
// By now we have established that the canonical constructor is the one to use
// and just need to gather implicit names to return
for (RawTypeName field : _recordFields) {
names.add(field.name);
}
return _primaryConstructor;
}
}
}