Fix `JavaClassWrapper` so it actually works

doc/classes/JavaClass.xml

@@ -1,13 +1,33 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <class name="JavaClass" inherits="RefCounted" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
 	<brief_description>
-		Represents an object from the Java Native Interface.
+		Represents a class from the Java Native Interface.
 	</brief_description>
 	<description>
-		Represents an object from the Java Native Interface. It is returned from [method JavaClassWrapper.wrap].
-		[b]Note:[/b] This class only works on Android. For any other build, this class does nothing.
+		Represents a class from the Java Native Interface. It is returned from [method JavaClassWrapper.wrap].
+		[b]Note:[/b] This class only works on Android. On any other platform, this class does nothing.
 		[b]Note:[/b] This class is not to be confused with [JavaScriptObject].
 	</description>
 	<tutorials>
 	</tutorials>
+	<methods>
+		<method name="get_java_class_name" qualifiers="const">
+			<return type="String" />
+			<description>
+				Returns the Java class name.
+			</description>
+		</method>
+		<method name="get_java_method_list" qualifiers="const">
+			<return type="Dictionary[]" />
+			<description>
+				Returns the object's Java methods and their signatures as an [Array] of dictionaries, in the same format as [method Object.get_method_list].
+			</description>
+		</method>
+		<method name="get_java_parent_class" qualifiers="const">
+			<return type="JavaClass" />
+			<description>
+				Returns a [JavaClass] representing the Java parent class of this class.
+			</description>
+		</method>
+	</methods>
 </class>

doc/classes/JavaClassWrapper.xml

@@ -6,6 +6,15 @@
 	<description>
 		The JavaClassWrapper singleton provides a way for the Godot application to send and receive data through the [url=https://developer.android.com/training/articles/perf-jni]Java Native Interface[/url] (JNI).
 		[b]Note:[/b] This singleton is only available in Android builds.
+		[codeblock]
+		var LocalDateTime = JavaClassWrapper.wrap("java.time.LocalDateTime")
+		var DateTimeFormatter = JavaClassWrapper.wrap("java.time.format.DateTimeFormatter")
+
+		var datetime = LocalDateTime.now()
+		var formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy HH:mm:ss")
+
+		print(datetime.format(formatter))
+		[/codeblock]
 	</description>
 	<tutorials>
 	</tutorials>

doc/classes/JavaObject.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<class name="JavaObject" inherits="RefCounted" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
+	<brief_description>
+		Represents an object from the Java Native Interface.
+	</brief_description>
+	<description>
+		Represents an object from the Java Native Interface. It can be returned from Java methods called on [JavaClass] or other [JavaObject]s. See [JavaClassWrapper] for an example.
+		[b]Note:[/b] This class only works on Android. On any other platform, this class does nothing.
+		[b]Note:[/b] This class is not to be confused with [JavaScriptObject].
+	</description>
+	<tutorials>
+	</tutorials>
+	<methods>
+		<method name="get_java_class" qualifiers="const">
+			<return type="JavaClass" />
+			<description>
+				Returns the [JavaClass] that this object is an instance of.
+			</description>
+		</method>
+	</methods>
+</class>

platform/android/api/api.cpp

@@ -49,6 +49,7 @@ void register_android_api() {
 #endif
 
 	GDREGISTER_CLASS(JavaClass);
+	GDREGISTER_CLASS(JavaObject);
 	GDREGISTER_CLASS(JavaClassWrapper);
 	Engine::get_singleton()->add_singleton(Engine::Singleton("JavaClassWrapper", JavaClassWrapper::get_singleton()));
 }
@@ -59,6 +60,16 @@ void unregister_android_api() {
 #endif
 }
 
+void JavaClass::_bind_methods() {
+	ClassDB::bind_method(D_METHOD("get_java_class_name"), &JavaClass::get_java_class_name);
+	ClassDB::bind_method(D_METHOD("get_java_method_list"), &JavaClass::get_java_method_list);
+	ClassDB::bind_method(D_METHOD("get_java_parent_class"), &JavaClass::get_java_parent_class);
+}
+
+void JavaObject::_bind_methods() {
+	ClassDB::bind_method(D_METHOD("get_java_class"), &JavaObject::get_java_class);
+}
+
 void JavaClassWrapper::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("wrap", "name"), &JavaClassWrapper::wrap);
 }
@@ -69,13 +80,32 @@ Variant JavaClass::callp(const StringName &, const Variant **, int, Callable::Ca
 	return Variant();
 }
 
+String JavaClass::get_java_class_name() const {
+	return "";
+}
+
+TypedArray<Dictionary> JavaClass::get_java_method_list() const {
+	return TypedArray<Dictionary>();
+}
+
+Ref<JavaClass> JavaClass::get_java_parent_class() const {
+	return Ref<JavaClass>();
+}
+
 JavaClass::JavaClass() {
 }
 
+JavaClass::~JavaClass() {
+}
+
 Variant JavaObject::callp(const StringName &, const Variant **, int, Callable::CallError &) {
 	return Variant();
 }
 
+Ref<JavaClass> JavaObject::get_java_class() const {
+	return Ref<JavaClass>();
+}
+
 JavaClassWrapper *JavaClassWrapper::singleton = nullptr;
 
 Ref<JavaClass> JavaClassWrapper::wrap(const String &) {

platform/android/api/java_class_wrapper.h

@@ -32,6 +32,7 @@
 #define JAVA_CLASS_WRAPPER_H
 
 #include "core/object/ref_counted.h"
+#include "core/variant/typed_array.h"
 
 #ifdef ANDROID_ENABLED
 #include <android/log.h>
@@ -67,6 +68,7 @@ class JavaClass : public RefCounted {
 
 	struct MethodInfo {
 		bool _static = false;
+		bool _constructor = false;
 		Vector<uint32_t> param_types;
 		Vector<StringName> param_sigs;
 		uint32_t return_type = 0;
@@ -174,14 +176,29 @@ class JavaClass : public RefCounted {
 	bool _call_method(JavaObject *p_instance, const StringName &p_method, const Variant **p_args, int p_argcount, Callable::CallError &r_error, Variant &ret);
 
 	friend class JavaClassWrapper;
+	friend class JavaObject;
+	String java_class_name;
+	String java_constructor_name;
 	HashMap<StringName, List<MethodInfo>> methods;
 	jclass _class;
 #endif
 
+protected:
+	static void _bind_methods();
+
 public:
 	virtual Variant callp(const StringName &p_method, const Variant **p_args, int p_argcount, Callable::CallError &r_error) override;
 
+	String get_java_class_name() const;
+	TypedArray<Dictionary> get_java_method_list() const;
+	Ref<JavaClass> get_java_parent_class() const;
+
+#ifdef ANDROID_ENABLED
+	virtual String to_string() override;
+#endif
+
 	JavaClass();
+	~JavaClass();
 };
 
 class JavaObject : public RefCounted {
@@ -191,14 +208,24 @@ class JavaObject : public RefCounted {
 	Ref<JavaClass> base_class;
 	friend class JavaClass;
 
-	jobject instance;
+	jobject instance = nullptr;
 #endif
 
+protected:
+	static void _bind_methods();
+
 public:
 	virtual Variant callp(const StringName &p_method, const Variant **p_args, int p_argcount, Callable::CallError &r_error) override;
 
+	Ref<JavaClass> get_java_class() const;
+
 #ifdef ANDROID_ENABLED
-	JavaObject(const Ref<JavaClass> &p_base, jobject *p_instance);
+	virtual String to_string() override;
+
+	jobject get_instance() { return instance; }
+
+	JavaObject();
+	JavaObject(const Ref<JavaClass> &p_base, jobject p_instance);
 	~JavaObject();
 #endif
 };
@@ -209,13 +236,17 @@ class JavaClassWrapper : public Object {
 #ifdef ANDROID_ENABLED
 	RBMap<String, Ref<JavaClass>> class_cache;
 	friend class JavaClass;
-	jmethodID getDeclaredMethods;
-	jmethodID getFields;
-	jmethodID getParameterTypes;
-	jmethodID getReturnType;
-	jmethodID getModifiers;
-	jmethodID getName;
+	jmethodID Class_getDeclaredConstructors;
+	jmethodID Class_getDeclaredMethods;
+	jmethodID Class_getFields;
 	jmethodID Class_getName;
+	jmethodID Class_getSuperclass;
+	jmethodID Constructor_getParameterTypes;
+	jmethodID Constructor_getModifiers;
+	jmethodID Method_getParameterTypes;
+	jmethodID Method_getReturnType;
+	jmethodID Method_getModifiers;
+	jmethodID Method_getName;
 	jmethodID Field_getName;
 	jmethodID Field_getModifiers;
 	jmethodID Field_get;
@@ -242,6 +273,8 @@ public:
 	Ref<JavaClass> wrap(const String &p_class);
 
 #ifdef ANDROID_ENABLED
+	Ref<JavaClass> wrap_jclass(jclass p_class);
+
 	JavaClassWrapper(jobject p_activity = nullptr);
 #else
 	JavaClassWrapper();

platform/android/api/jni_singleton.h

@@ -180,6 +180,11 @@ public:
 				env->DeleteLocalRef(obj);
 
 			} break;
+			case Variant::OBJECT: {
+				jobject obj = env->CallObjectMethodA(instance, E->get().method, v);
+				ret = _jobject_to_variant(env, obj);
+				env->DeleteLocalRef(obj);
+			} break;
 			default: {
 				env->PopLocalFrame(nullptr);
 				ERR_FAIL_V(Variant());

platform/android/java_class_wrapper.cpp

@@ -44,7 +44,7 @@ bool JavaClass::_call_method(JavaObject *p_instance, const StringName &p_method,
 
 	MethodInfo *method = nullptr;
 	for (MethodInfo &E : M->value) {
-		if (!p_instance && !E._static) {
+		if (!p_instance && !E._static && !E._constructor) {
 			r_error.error = Callable::CallError::CALL_ERROR_INSTANCE_IS_NULL;
 			continue;
 		}
@@ -102,15 +102,19 @@ bool JavaClass::_call_method(JavaObject *p_instance, const StringName &p_method,
 					}
 				} break;
 				case ARG_TYPE_CLASS: {
-					if (p_args[i]->get_type() != Variant::OBJECT) {
+					if (p_args[i]->get_type() != Variant::OBJECT && p_args[i]->get_type() != Variant::NIL) {
 						arg_expected = Variant::OBJECT;
 					} else {
 						Ref<RefCounted> ref = *p_args[i];
-						if (!ref.is_null()) {
+						if (ref.is_valid()) {
 							if (Object::cast_to<JavaObject>(ref.ptr())) {
 								Ref<JavaObject> jo = ref;
 								//could be faster
-								jclass c = env->FindClass(E.param_sigs[i].operator String().utf8().get_data());
+								String cn = E.param_sigs[i].operator String();
+								if (cn.begins_with("L") && cn.ends_with(";")) {
+									cn = cn.substr(1, cn.length() - 2);
+								}
+								jclass c = env->FindClass(cn.utf8().get_data());
 								if (!c || !env->IsInstanceOf(jo->instance, c)) {
 									arg_expected = Variant::OBJECT;
 								} else {
@@ -458,7 +462,9 @@ bool JavaClass::_call_method(JavaObject *p_instance, const StringName &p_method,
 		} break;
 		default: {
 			jobject obj;
-			if (method->_static) {
+			if (method->_constructor) {
+				obj = env->NewObject(_class, method->method, argv);
+			} else if (method->_static) {
 				obj = env->CallStaticObjectMethodA(_class, method->method, argv);
 			} else {
 				obj = env->CallObjectMethodA(p_instance->instance, method->method, argv);
@@ -487,7 +493,9 @@ bool JavaClass::_call_method(JavaObject *p_instance, const StringName &p_method,
 
 Variant JavaClass::callp(const StringName &p_method, const Variant **p_args, int p_argcount, Callable::CallError &r_error) {
 	Variant ret;
-	bool found = _call_method(nullptr, p_method, p_args, p_argcount, r_error, ret);
+
+	String method = (p_method == java_constructor_name) ? "<init>" : p_method;
+	bool found = _call_method(nullptr, method, p_args, p_argcount, r_error, ret);
 	if (found) {
 		return ret;
 	}
@@ -495,19 +503,156 @@ Variant JavaClass::callp(const StringName &p_method, const Variant **p_args, int
 	return RefCounted::callp(p_method, p_args, p_argcount, r_error);
 }
 
+String JavaClass::get_java_class_name() const {
+	return java_class_name;
+}
+
+TypedArray<Dictionary> JavaClass::get_java_method_list() const {
+	TypedArray<Dictionary> method_list;
+
+	for (const KeyValue<StringName, List<MethodInfo>> &item : methods) {
+		for (const MethodInfo &mi : item.value) {
+			Dictionary method;
+
+			method["name"] = mi._constructor ? java_constructor_name : String(item.key);
+			method["id"] = (uint64_t)mi.method;
+			method["default_args"] = Array();
+			method["flags"] = METHOD_FLAGS_DEFAULT & (mi._static || mi._constructor ? METHOD_FLAG_STATIC : METHOD_FLAG_NORMAL);
+
+			{
+				Array a;
+
+				for (uint32_t argtype : mi.param_types) {
+					Dictionary d;
+
+					Variant::Type t = Variant::NIL;
+					float likelihood = 0.0;
+					_convert_to_variant_type(argtype, t, likelihood);
+					d["type"] = t;
+					if (t == Variant::OBJECT) {
+						d["hint"] = PROPERTY_HINT_RESOURCE_TYPE;
+						d["hint_string"] = "JavaObject";
+					} else {
+						d["hint"] = 0;
+						d["hint_string"] = "";
+					}
+
+					a.push_back(d);
+				}
+
+				method["args"] = a;
+			}
+
+			{
+				Dictionary d;
+
+				if (mi._constructor) {
+					d["type"] = Variant::OBJECT;
+					d["hint"] = PROPERTY_HINT_RESOURCE_TYPE;
+					d["hint_string"] = "JavaObject";
+				} else {
+					Variant::Type t = Variant::NIL;
+					float likelihood = 0.0;
+					_convert_to_variant_type(mi.return_type, t, likelihood);
+					d["type"] = t;
+					if (t == Variant::OBJECT) {
+						d["hint"] = PROPERTY_HINT_RESOURCE_TYPE;
+						d["hint_string"] = "JavaObject";
+					} else {
+						d["hint"] = 0;
+						d["hint_string"] = "";
+					}
+				}
+
+				method["return_type"] = d;
+			}
+
+			method_list.push_back(method);
+		}
+	}
+
+	return method_list;
+}
+
+Ref<JavaClass> JavaClass::get_java_parent_class() const {
+	ERR_FAIL_NULL_V(_class, Ref<JavaClass>());
+
+	JNIEnv *env = get_jni_env();
+	ERR_FAIL_NULL_V(env, Ref<JavaClass>());
+
+	jclass superclass = (jclass)env->CallObjectMethod(_class, JavaClassWrapper::singleton->Class_getSuperclass);
+	if (!superclass) {
+		return Ref<JavaClass>();
+	}
+
+	Ref<JavaClass> ret = JavaClassWrapper::singleton->wrap_jclass(superclass);
+	env->DeleteLocalRef(superclass);
+	return ret;
+}
+
+String JavaClass::to_string() {
+	return "<JavaClass:" + java_class_name + ">";
+}
+
 JavaClass::JavaClass() {
 }
 
+JavaClass::~JavaClass() {
+	if (_class) {
+		JNIEnv *env = get_jni_env();
+		ERR_FAIL_NULL(env);
+
+		env->DeleteGlobalRef(_class);
+	}
+}
+
 /////////////////////
 
 Variant JavaObject::callp(const StringName &p_method, const Variant **p_args, int p_argcount, Callable::CallError &r_error) {
-	return Variant();
+	if (instance) {
+		Ref<JavaClass> c = base_class;
+		while (c.is_valid()) {
+			Variant ret;
+			bool found = c->_call_method(this, p_method, p_args, p_argcount, r_error, ret);
+			if (found) {
+				return ret;
+			}
+			c = c->get_java_parent_class();
+		}
+	}
+
+	return RefCounted::callp(p_method, p_args, p_argcount, r_error);
+}
+
+Ref<JavaClass> JavaObject::get_java_class() const {
+	return base_class;
 }
 
-JavaObject::JavaObject(const Ref<JavaClass> &p_base, jobject *p_instance) {
+String JavaObject::to_string() {
+	if (base_class.is_valid() && instance) {
+		return "<JavaObject:" + base_class->java_class_name + " \"" + (String)call("toString") + "\">";
+	}
+	return RefCounted::to_string();
+}
+
+JavaObject::JavaObject() {
+}
+
+JavaObject::JavaObject(const Ref<JavaClass> &p_base, jobject p_instance) {
+	JNIEnv *env = get_jni_env();
+	ERR_FAIL_NULL(env);
+
+	base_class = p_base;
+	instance = env->NewGlobalRef(p_instance);
 }
 
 JavaObject::~JavaObject() {
+	if (instance) {
+		JNIEnv *env = get_jni_env();
+		ERR_FAIL_NULL(env);
+
+		env->DeleteGlobalRef(instance);
+	}
 }
 
 ////////////////////
@@ -649,6 +794,16 @@ bool JavaClass::_convert_object_to_variant(JNIEnv *env, jobject obj, Variant &va
 			return true;
 		} break;
 		case ARG_TYPE_CLASS: {
+			jclass java_class = env->GetObjectClass(obj);
+			Ref<JavaClass> java_class_wrapped = JavaClassWrapper::singleton->wrap_jclass(java_class);
+			env->DeleteLocalRef(java_class);
+
+			if (java_class_wrapped.is_valid()) {
+				Ref<JavaObject> ret = Ref<JavaObject>(memnew(JavaObject(java_class_wrapped, obj)));
+				var = ret;
+				return true;
+			}
+
 			return false;
 		} break;
 		case ARG_ARRAY_BIT | ARG_TYPE_VOID: {
@@ -966,43 +1121,67 @@ bool JavaClass::_convert_object_to_variant(JNIEnv *env, jobject obj, Variant &va
 }
 
 Ref<JavaClass> JavaClassWrapper::wrap(const String &p_class) {
-	if (class_cache.has(p_class)) {
-		return class_cache[p_class];
+	String class_name_dots = p_class.replace("/", ".");
+	if (class_cache.has(class_name_dots)) {
+		return class_cache[class_name_dots];
 	}
 
 	JNIEnv *env = get_jni_env();
 	ERR_FAIL_NULL_V(env, Ref<JavaClass>());
 
-	jclass bclass = env->FindClass(p_class.utf8().get_data());
+	jclass bclass = env->FindClass(class_name_dots.replace(".", "/").utf8().get_data());
 	ERR_FAIL_NULL_V(bclass, Ref<JavaClass>());
 
-	jobjectArray methods = (jobjectArray)env->CallObjectMethod(bclass, getDeclaredMethods);
+	jobjectArray constructors = (jobjectArray)env->CallObjectMethod(bclass, Class_getDeclaredConstructors);
+	ERR_FAIL_NULL_V(constructors, Ref<JavaClass>());
 
+	jobjectArray methods = (jobjectArray)env->CallObjectMethod(bclass, Class_getDeclaredMethods);
 	ERR_FAIL_NULL_V(methods, Ref<JavaClass>());
 
 	Ref<JavaClass> java_class = memnew(JavaClass);
+	java_class->java_class_name = class_name_dots;
+	Vector<String> class_name_parts = class_name_dots.split(".");
+	java_class->java_constructor_name = class_name_parts[class_name_parts.size() - 1];
+	java_class->_class = (jclass)env->NewGlobalRef(bclass);
+	class_cache[class_name_dots] = java_class;
+
+	LocalVector<jobject> methods_and_constructors;
+	int constructor_count = env->GetArrayLength(constructors);
+	int method_count = env->GetArrayLength(methods);
+	methods_and_constructors.resize(method_count + constructor_count);
+	for (int i = 0; i < constructor_count; i++) {
+		methods_and_constructors[i] = env->GetObjectArrayElement(constructors, i);
+	}
+	for (int i = 0; i < method_count; i++) {
+		methods_and_constructors[constructor_count + i] = env->GetObjectArrayElement(methods, i);
+	}
 
-	int count = env->GetArrayLength(methods);
-
-	for (int i = 0; i < count; i++) {
-		jobject obj = env->GetObjectArrayElement(methods, i);
+	for (int i = 0; i < (int)methods_and_constructors.size(); i++) {
+		jobject obj = methods_and_constructors[i];
 		ERR_CONTINUE(!obj);
 
-		jstring name = (jstring)env->CallObjectMethod(obj, getName);
-		String str_method = jstring_to_string(name, env);
-		env->DeleteLocalRef(name);
+		bool is_constructor = i < constructor_count;
+
+		String str_method;
+		if (is_constructor) {
+			str_method = "<init>";
+		} else {
+			jstring name = (jstring)env->CallObjectMethod(obj, Method_getName);
+			str_method = jstring_to_string(name, env);
+			env->DeleteLocalRef(name);
+		}
 
 		Vector<String> params;
 
-		jint mods = env->CallIntMethod(obj, getModifiers);
+		jint mods = env->CallIntMethod(obj, is_constructor ? Constructor_getModifiers : Method_getModifiers);
 
 		if (!(mods & 0x0001)) {
 			env->DeleteLocalRef(obj);
 			continue; //not public bye
 		}
 
-		jobjectArray param_types = (jobjectArray)env->CallObjectMethod(obj, getParameterTypes);
-		int count2 = env->GetArrayLength(param_types);
+		jobjectArray param_types = (jobjectArray)env->CallObjectMethod(obj, is_constructor ? Constructor_getParameterTypes : Method_getParameterTypes);
+		int count = env->GetArrayLength(param_types);
 
 		if (!java_class->methods.has(str_method)) {
 			java_class->methods[str_method] = List<JavaClass::MethodInfo>();
@@ -1010,10 +1189,11 @@ Ref<JavaClass> JavaClassWrapper::wrap(const String &p_class) {
 
 		JavaClass::MethodInfo mi;
 		mi._static = (mods & 0x8) != 0;
+		mi._constructor = is_constructor;
 		bool valid = true;
 		String signature = "(";
 
-		for (int j = 0; j < count2; j++) {
+		for (int j = 0; j < count; j++) {
 			jobject obj2 = env->GetObjectArrayElement(param_types, j);
 			String strsig;
 			uint32_t sig = 0;
@@ -1029,7 +1209,7 @@ Ref<JavaClass> JavaClassWrapper::wrap(const String &p_class) {
 		}
 
 		if (!valid) {
-			print_line("Method can't be bound (unsupported arguments): " + p_class + "::" + str_method);
+			print_line("Method can't be bound (unsupported arguments): " + class_name_dots + "::" + str_method);
 			env->DeleteLocalRef(obj);
 			env->DeleteLocalRef(param_types);
 			continue;
@@ -1037,21 +1217,28 @@ Ref<JavaClass> JavaClassWrapper::wrap(const String &p_class) {
 
 		signature += ")";
 
-		jobject return_type = (jobject)env->CallObjectMethod(obj, getReturnType);
+		if (is_constructor) {
+			signature += "V";
+			mi.return_type = JavaClass::ARG_TYPE_CLASS;
+		} else {
+			jobject return_type = (jobject)env->CallObjectMethod(obj, Method_getReturnType);
+
+			String strsig;
+			uint32_t sig = 0;
+			if (!_get_type_sig(env, return_type, sig, strsig)) {
+				print_line("Method can't be bound (unsupported return type): " + class_name_dots + "::" + str_method);
+				env->DeleteLocalRef(obj);
+				env->DeleteLocalRef(param_types);
+				env->DeleteLocalRef(return_type);
+				continue;
+			}
+
+			signature += strsig;
+			mi.return_type = sig;
 
-		String strsig;
-		uint32_t sig = 0;
-		if (!_get_type_sig(env, return_type, sig, strsig)) {
-			print_line("Method can't be bound (unsupported return type): " + p_class + "::" + str_method);
-			env->DeleteLocalRef(obj);
-			env->DeleteLocalRef(param_types);
 			env->DeleteLocalRef(return_type);
-			continue;
 		}
 
-		signature += strsig;
-		mi.return_type = sig;
-
 		bool discard = false;
 
 		for (List<JavaClass::MethodInfo>::Element *E = java_class->methods[str_method].front(); E; E = E->next()) {
@@ -1103,14 +1290,14 @@ Ref<JavaClass> JavaClassWrapper::wrap(const String &p_class) {
 
 		env->DeleteLocalRef(obj);
 		env->DeleteLocalRef(param_types);
-		env->DeleteLocalRef(return_type);
 	}
 
+	env->DeleteLocalRef(constructors);
 	env->DeleteLocalRef(methods);
 
-	jobjectArray fields = (jobjectArray)env->CallObjectMethod(bclass, getFields);
+	jobjectArray fields = (jobjectArray)env->CallObjectMethod(bclass, Class_getFields);
 
-	count = env->GetArrayLength(fields);
+	int count = env->GetArrayLength(fields);
 
 	for (int i = 0; i < count; i++) {
 		jobject obj = env->GetObjectArrayElement(fields, i);
@@ -1146,7 +1333,18 @@ Ref<JavaClass> JavaClassWrapper::wrap(const String &p_class) {
 
 	env->DeleteLocalRef(fields);
 
-	return Ref<JavaClass>();
+	return java_class;
+}
+
+Ref<JavaClass> JavaClassWrapper::wrap_jclass(jclass p_class) {
+	JNIEnv *env = get_jni_env();
+	ERR_FAIL_NULL_V(env, Ref<JavaClass>());
+
+	jstring class_name = (jstring)env->CallObjectMethod(p_class, Class_getName);
+	String class_name_string = jstring_to_string(class_name, env);
+	env->DeleteLocalRef(class_name);
+
+	return wrap(class_name_string);
 }
 
 JavaClassWrapper *JavaClassWrapper::singleton = nullptr;
@@ -1158,16 +1356,23 @@ JavaClassWrapper::JavaClassWrapper(jobject p_activity) {
 	ERR_FAIL_NULL(env);
 
 	jclass bclass = env->FindClass("java/lang/Class");
-	getDeclaredMethods = env->GetMethodID(bclass, "getDeclaredMethods", "()[Ljava/lang/reflect/Method;");
-	getFields = env->GetMethodID(bclass, "getFields", "()[Ljava/lang/reflect/Field;");
+	Class_getDeclaredConstructors = env->GetMethodID(bclass, "getDeclaredConstructors", "()[Ljava/lang/reflect/Constructor;");
+	Class_getDeclaredMethods = env->GetMethodID(bclass, "getDeclaredMethods", "()[Ljava/lang/reflect/Method;");
+	Class_getFields = env->GetMethodID(bclass, "getFields", "()[Ljava/lang/reflect/Field;");
 	Class_getName = env->GetMethodID(bclass, "getName", "()Ljava/lang/String;");
+	Class_getSuperclass = env->GetMethodID(bclass, "getSuperclass", "()Ljava/lang/Class;");
+	env->DeleteLocalRef(bclass);
+
+	bclass = env->FindClass("java/lang/reflect/Constructor");
+	Constructor_getParameterTypes = env->GetMethodID(bclass, "getParameterTypes", "()[Ljava/lang/Class;");
+	Constructor_getModifiers = env->GetMethodID(bclass, "getModifiers", "()I");
 	env->DeleteLocalRef(bclass);
 
 	bclass = env->FindClass("java/lang/reflect/Method");
-	getParameterTypes = env->GetMethodID(bclass, "getParameterTypes", "()[Ljava/lang/Class;");
-	getReturnType = env->GetMethodID(bclass, "getReturnType", "()Ljava/lang/Class;");
-	getName = env->GetMethodID(bclass, "getName", "()Ljava/lang/String;");
-	getModifiers = env->GetMethodID(bclass, "getModifiers", "()I");
+	Method_getParameterTypes = env->GetMethodID(bclass, "getParameterTypes", "()[Ljava/lang/Class;");
+	Method_getReturnType = env->GetMethodID(bclass, "getReturnType", "()Ljava/lang/Class;");
+	Method_getName = env->GetMethodID(bclass, "getName", "()Ljava/lang/String;");
+	Method_getModifiers = env->GetMethodID(bclass, "getModifiers", "()I");
 	env->DeleteLocalRef(bclass);
 
 	bclass = env->FindClass("java/lang/reflect/Field");

platform/android/jni_utils.cpp

@@ -30,6 +30,8 @@
 
 #include "jni_utils.h"
 
+#include "api/java_class_wrapper.h"
+
 jvalret _variant_to_jvalue(JNIEnv *env, Variant::Type p_type, const Variant *p_arg, bool force_jobject) {
 	jvalret v;
 
@@ -185,6 +187,16 @@ jvalret _variant_to_jvalue(JNIEnv *env, Variant::Type p_type, const Variant *p_a
 			v.obj = arr;
 
 		} break;
+		case Variant::OBJECT: {
+			Ref<JavaObject> generic_object = *p_arg;
+			if (generic_object.is_valid()) {
+				jobject obj = env->NewLocalRef(generic_object->get_instance());
+				v.val.l = obj;
+				v.obj = obj;
+			} else {
+				v.val.i = 0;
+			}
+		} break;
 
 		default: {
 			v.val.i = 0;
@@ -358,9 +370,11 @@ Variant _jobject_to_variant(JNIEnv *env, jobject obj) {
 		return ret;
 	}
 
+	Ref<JavaObject> generic_object(memnew(JavaObject(JavaClassWrapper::get_singleton()->wrap(name), obj)));
+
 	env->DeleteLocalRef(c);
 
-	return Variant();
+	return generic_object;
 }
 
 Variant::Type get_jni_type(const String &p_type) {
@@ -395,10 +409,10 @@ Variant::Type get_jni_type(const String &p_type) {
 		idx++;
 	}
 
-	return Variant::NIL;
+	return Variant::OBJECT;
 }
 
-const char *get_jni_sig(const String &p_type) {
+String get_jni_sig(const String &p_type) {
 	static struct {
 		const char *name;
 		const char *sig;
@@ -430,5 +444,5 @@ const char *get_jni_sig(const String &p_type) {
 		idx++;
 	}
 
-	return "Ljava/lang/Object;";
+	return "L" + p_type.replace(".", "/") + ";";
 }

platform/android/jni_utils.h

@@ -52,6 +52,6 @@ Variant _jobject_to_variant(JNIEnv *env, jobject obj);
 
 Variant::Type get_jni_type(const String &p_type);
 
-const char *get_jni_sig(const String &p_type);
+String get_jni_sig(const String &p_type);
 
 #endif // JNI_UTILS_H