Add compile-time generation of JNI class names

As with method signatures, register class names using template function
specialization in the QtJniTypes namespace, and then declare C++ types
as JNI classes with a class name string. Such classes implicitly get
registered as JNI types as well.

Add a QJniObject construct method (since C++ constructors that are
templates cannot be explicitly instantiated with a type), and a
QJniEnvironment::findClass overload.

Add test coverage, also for the recently added macros for native
methods.

As a drive-by, change the name of the Q_JNI_DECLARE_NATIVE_METHOD
macro to Q_DECLARE_JNI_NATIVE_METHOD for consistency.

Change-Id: Ic19562d78da726f202b3bdf4e9354e8ad24d8bd9
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>

6 files changed, 79 insertions, 6 deletions

diff --git a/src/corelib/kernel/qjnienvironment.h b/src/corelib/kernel/qjnienvironment.h
index 6cc8693227..f7ffa836c2 100644
--- a/src/corelib/kernel/qjnienvironment.h
+++ b/src/corelib/kernel/qjnienvironment.h
@@ -24,6 +24,8 @@ public:
     JNIEnv &operator*() const;
     JNIEnv *jniEnv() const;
     jclass findClass(const char *className);
+    template<typename Class>
+    jclass findClass() { return findClass(QtJniTypes::className<Class>().data()); }
     jmethodID findMethod(jclass clazz, const char *methodName, const char *signature);
     template<typename ...Args>
     jmethodID findMethod(jclass clazz, const char *methodName) {
diff --git a/src/corelib/kernel/qjniobject.h b/src/corelib/kernel/qjniobject.h
index bbaa6ee70c..3c7ca13ff2 100644
--- a/src/corelib/kernel/qjniobject.h
+++ b/src/corelib/kernel/qjniobject.h
@@ -45,6 +45,14 @@ public:
     inline QJniObject(QtJniTypes::Object wrapper) noexcept : QJniObject(jobject(wrapper)) {}
     ~QJniObject();
 
+    template<typename Class, typename ...Args>
+    static inline QJniObject construct(Args &&...args)
+    {
+        return QJniObject(QtJniTypes::className<Class>().data(),
+                          QtJniTypes::constructorSignature<Args...>().data(),
+                          std::forward<Args>(args)...);
+    }
+
     jobject object() const;
     template <typename T> T object() const
     {
diff --git a/src/corelib/kernel/qjnitypes.h b/src/corelib/kernel/qjnitypes.h
index 0ebc1a6bc9..ecb8ae02f9 100644
--- a/src/corelib/kernel/qjnitypes.h
+++ b/src/corelib/kernel/qjnitypes.h
@@ -214,6 +214,21 @@ constexpr auto typeSignature()
         staticAssertTypeMismatch();
 }
 
+template<bool flag = false>
+static void staticAssertClassNotRegistered()
+{
+    static_assert(flag, "Class not registered, use Q_DECLARE_JNI_CLASS");
+}
+
+template<typename T>
+constexpr auto className()
+{
+    if constexpr(std::is_same<T, jstring>::value)
+        return String("java/lang/String");
+    else
+        staticAssertClassNotRegistered();
+}
+
 template<typename T>
 static constexpr bool isPrimitiveType()
 {
@@ -298,13 +313,17 @@ struct Object
 
 } // namespace QtJniTypes
 
-#define Q_DECLARE_JNI_TYPE(Type, Signature)                      \
+#define Q_DECLARE_JNI_TYPE_HELPER(Type)                         \
 namespace QtJniTypes {                                          \
 struct Type : Object                                            \
 {                                                               \
     constexpr Type(jobject o) noexcept : Object{o} {}           \
 };                                                              \
 }                                                               \
+
+
+#define Q_DECLARE_JNI_TYPE(Type, Signature)                     \
+Q_DECLARE_JNI_TYPE_HELPER(Type)                                 \
 template<>                                                      \
 constexpr auto QtJniTypes::typeSignature<QtJniTypes::Type>()    \
 {                                                               \
@@ -315,7 +334,23 @@ constexpr auto QtJniTypes::typeSignature<QtJniTypes::Type>()    \
     return QtJniTypes::String(Signature);                       \
 }                                                               \
 
-#define Q_JNI_DECLARE_NATIVE_METHOD(Method)                     \
+#define Q_DECLARE_JNI_CLASS(Type, Signature)                    \
+Q_DECLARE_JNI_TYPE_HELPER(Type)                                 \
+template<>                                                      \
+constexpr auto QtJniTypes::className<QtJniTypes::Type>()        \
+{                                                               \
+    return QtJniTypes::String(Signature);                       \
+}                                                               \
+template<>                                                      \
+constexpr auto QtJniTypes::typeSignature<QtJniTypes::Type>()    \
+{                                                               \
+    return QtJniTypes::String("L")                              \
+         + QtJniTypes::String(Signature)                        \
+         + QtJniTypes::String(";");                             \
+}                                                               \
+
+
+#define Q_DECLARE_JNI_NATIVE_METHOD(Method)                     \
 namespace QtJniMethods {                                        \
 static constexpr auto Method##_signature =                      \
     QtJniTypes::nativeMethodSignature(Method);                  \
diff --git a/tests/auto/corelib/kernel/qjnienvironment/tst_qjnienvironment.cpp b/tests/auto/corelib/kernel/qjnienvironment/tst_qjnienvironment.cpp
index f699d6816a..76cad4ddc0 100644
--- a/tests/auto/corelib/kernel/qjnienvironment/tst_qjnienvironment.cpp
+++ b/tests/auto/corelib/kernel/qjnienvironment/tst_qjnienvironment.cpp
@@ -65,6 +65,7 @@ void tst_QJniEnvironment::jniEnv()
         // try to find an existing class with QJniEnvironment
         QJniEnvironment env;
         QVERIFY(env.findClass("java/lang/Object"));
+        QVERIFY(env.findClass<jstring>());
 
         // try to find a nonexistent class
         QVERIFY(!env.findClass("this/doesnt/Exist"));
@@ -98,14 +99,14 @@ static void callbackFromJava(JNIEnv *env, jobject /*thiz*/, jstring value)
     Q_UNUSED(env)
     registerNativesString = QJniObject(value).toString();
 }
-Q_JNI_DECLARE_NATIVE_METHOD(callbackFromJava);
+Q_DECLARE_JNI_NATIVE_METHOD(callbackFromJava);
 
 static void callbackFromJavaNoCtor(JNIEnv *env, jobject /*thiz*/, jstring value)
 {
     Q_UNUSED(env)
     registerNativesString = QJniObject(value).toString();
 }
-Q_JNI_DECLARE_NATIVE_METHOD(callbackFromJavaNoCtor);
+Q_DECLARE_JNI_NATIVE_METHOD(callbackFromJavaNoCtor);
 
 void tst_QJniEnvironment::registerNativeMethods()
 {
@@ -145,7 +146,7 @@ static void intCallbackFromJava(JNIEnv *env, jobject /*thiz*/, jint value)
     Q_UNUSED(env)
     registerNativeInteger = static_cast<int>(value);
 }
-Q_JNI_DECLARE_NATIVE_METHOD(intCallbackFromJava);
+Q_DECLARE_JNI_NATIVE_METHOD(intCallbackFromJava);
 
 void tst_QJniEnvironment::registerNativeMethodsByJclass()
 {
diff --git a/tests/auto/corelib/kernel/qjniobject/tst_qjniobject.cpp b/tests/auto/corelib/kernel/qjniobject/tst_qjniobject.cpp
index 8faa9b6fbb..e57785c5c5 100644
--- a/tests/auto/corelib/kernel/qjniobject/tst_qjniobject.cpp
+++ b/tests/auto/corelib/kernel/qjniobject/tst_qjniobject.cpp
@@ -135,6 +135,11 @@ void tst_QJniObject::ctor()
     }
 
     {
+        QJniObject object = QJniObject::construct<jstring>();
+        QVERIFY(object.isValid());
+    }
+
+    {
         QJniObject string = QJniObject::fromString(QLatin1String("Hello, Java"));
         QJniObject object("java/lang/String", "(Ljava/lang/String;)V", string.object<jstring>());
         QVERIFY(object.isValid());
@@ -143,7 +148,7 @@ void tst_QJniObject::ctor()
 
     {
         QJniObject string = QJniObject::fromString(QLatin1String("Hello, Java"));
-        QJniObject object("java/lang/String", string.object<jstring>());
+        QJniObject object = QJniObject::construct<jstring>(string.object<jstring>());
         QVERIFY(object.isValid());
         QCOMPARE(string.toString(), object.toString());
     }
diff --git a/tests/auto/corelib/kernel/qjnitypes/tst_qjnitypes.cpp b/tests/auto/corelib/kernel/qjnitypes/tst_qjnitypes.cpp
index c4abfe399a..395028b8cb 100644
--- a/tests/auto/corelib/kernel/qjnitypes/tst_qjnitypes.cpp
+++ b/tests/auto/corelib/kernel/qjnitypes/tst_qjnitypes.cpp
@@ -14,6 +14,7 @@ public:
 
 private slots:
     void initTestCase();
+    void nativeMethod();
 };
 
 struct QtJavaWrapper {};
@@ -45,6 +46,11 @@ static_assert(QtJniTypes::typeSignature<QtJniTypes::JavaType>() == "Lorg/qtproje
 Q_DECLARE_JNI_TYPE(ArrayType, "[Lorg/qtproject/qt/ArrayType;")
 static_assert(QtJniTypes::typeSignature<QtJniTypes::ArrayType>() == "[Lorg/qtproject/qt/ArrayType;");
 
+static_assert(QtJniTypes::className<jstring>() == "java/lang/String");
+
+Q_DECLARE_JNI_CLASS(QtTextToSpeech, "org/qtproject/qt/android/speech/QtTextToSpeech")
+static_assert(QtJniTypes::className<QtJniTypes::QtTextToSpeech>() == "org/qtproject/qt/android/speech/QtTextToSpeech");
+
 static_assert(QtJniTypes::fieldSignature<jint>() == "I");
 static_assert(QtJniTypes::fieldSignature<jint>() != "X");
 static_assert(QtJniTypes::fieldSignature<jint>() != "Ljava/lang/Object;");
@@ -97,6 +103,22 @@ void tst_QJniTypes::initTestCase()
 
 }
 
+static bool nativeFunction(JNIEnv *, jclass, int, jstring, long)
+{
+    return true;
+}
+Q_DECLARE_JNI_NATIVE_METHOD(nativeFunction)
+
+static_assert(QtJniTypes::nativeMethodSignature(nativeFunction) == "(ILjava/lang/String;J)Z");
+
+void tst_QJniTypes::nativeMethod()
+{
+    const auto method = Q_JNI_NATIVE_METHOD(nativeFunction);
+    QVERIFY(method.fnPtr == nativeFunction);
+    QCOMPARE(method.name, "nativeFunction");
+    QCOMPARE(method.signature, "(ILjava/lang/String;J)Z");
+}
+
 QTEST_MAIN(tst_QJniTypes)
 
 #include "tst_qjnitypes.moc"