functions.

Functions
Jni::org::qore::jni::Class	Jni::org::qore::jni::define_class (string name, binary bytecode)
	Creates a class object from bytecode data. More...
string	Jni::org::qore::jni::get_version ()
	Returns the version of the JNI API. More...
Jni::java::lang::Object	Jni::org::qore::jni::implement_interface (Jni::org::qore::jni::QoreInvocationHandler invocationHandler, Jni::java::lang::Class cls)
	Creates a Java object that implements given interface using an invocation handler. More...
Jni::java::lang::Object	Jni::org::qore::jni::implement_interface (Jni::java::lang::ClassLoader classLoader, Jni::org::qore::jni::QoreInvocationHandler invocationHandler, Jni::java::lang::Class cls)
	Creates a Java object that implements given interface using an invocation handler using an explicit class loader. More...
Jni::java::lang::Object	Jni::org::qore::jni::invoke (Jni::java::lang::reflect::Method method, *Jni::java::lang::Object object,...)
	Invokes a method with the given arguments in a virtual way; meaning that the method in the most derived class is executed; not necessarily the method passed as an argument. More...
Jni::java::lang::Object	Jni::org::qore::jni::invoke_nonvirtual (Jni::java::lang::reflect::Method method, *Jni::java::lang::Object object,...)
	Invokes a method with the given arguments in a non-virtual way; meaning that even if the object provided is a child class, the method given in the first argument is executed. More...
Jni::java::lang::Class	Jni::org::qore::jni::load_class (string name)
	Loads a Java class with given name. More...
Jni::org::qore::jni::JavaArray	Jni::org::qore::jni::new_array (Jni::java::lang::Class cls, int size)
	Allocates a new Java array. More...
	Jni::org::qore::jni::set_save_object_callback (*code save_object_callback)
	Sets the "save object" callback for Qore objects created from Java code. More...

Detailed Description

Function Documentation

define_class()

Jni::org::qore::jni::Class Jni::org::qore::jni::define_class	(	string	name,
		binary	bytecode
	)

Creates a class object from bytecode data.

Example:

java::lang::Class cls = define_class(name, bytecode);

Parameters

name	the name of the class (ex: "org/qore/my_package/ClassName")
bytecode	the byte code of the class

Note

the class will be created using the classloader for the containing Program object

Since

jni 1.1

get_version()

string Jni::org::qore::jni::get_version

(

)

Returns the version of the JNI API.

Returns

the version of the JNI API

implement_interface() [1/2]

Jni::java::lang::Object Jni::org::qore::jni::implement_interface	(	Jni::java::lang::ClassLoader	classLoader,
		Jni::org::qore::jni::QoreInvocationHandler	invocationHandler,
		Jni::java::lang::Class	cls
	)

Creates a Java object that implements given interface using an invocation handler using an explicit class loader.

Parameters

classLoader	the class loader that loaded the interface
invocationHandler	the invocation handler
cls	the interface to implement

Returns

a Java object that implements the interface by calling the invocation handler

Example:

ClassLoader classLoader = ...;
Class runnableClass = load_class("java/lang/Runnable");
QoreInvocationHandler h(any sub(Method m, *list args) { doRun(); });
Object runnableInstance = Jni::implement_interface(classLoader, h, runnableClass);
# runnableInstance now has a Java method void run() that calls Qore function doRun()

implement_interface() [2/2]

Jni::java::lang::Object Jni::org::qore::jni::implement_interface	(	Jni::org::qore::jni::QoreInvocationHandler	invocationHandler,
		Jni::java::lang::Class	cls
	)

Creates a Java object that implements given interface using an invocation handler.

Parameters

invocationHandler	the invocation handler
cls	the interface to implement

Returns

a Java object that implements the interface by calling the invocation handler

Example:

Class runnableClass = Jni::load_class("java/lang/Runnable");
QoreInvocationHandler h(any sub(Method m, *list args) { doRun(); });
Object runnableInstance = Jni::implement_interface(h, runnableClass);
# runnableInstance now has a Java method void run() that calls Qore function doRun()

invoke()

Jni::java::lang::Object Jni::org::qore::jni::invoke	(	Jni::java::lang::reflect::Method	method,
		*Jni::java::lang::Object	object,
			...
	)

Invokes a method with the given arguments in a virtual way; meaning that the method in the most derived class is executed; not necessarily the method passed as an argument.

Parameters

method	the method to invoke
object	the object to use to invoke the method; for static methods, this argument can be nothing

Note

• reflection is not used, so exceptions are thrown directly (i.e. not wrapped as java.lang.reflect.InvocationTargetException objects)
• for static method invocations, this function is identical to invoke_nonvirtual()

invoke_nonvirtual()

Jni::java::lang::Object Jni::org::qore::jni::invoke_nonvirtual	(	Jni::java::lang::reflect::Method	method,
		*Jni::java::lang::Object	object,
			...
	)

Invokes a method with the given arguments in a non-virtual way; meaning that even if the object provided is a child class, the method given in the first argument is executed.

Parameters

method	the method to invoke
object	the object to use to invoke the method; for static methods, this argument can be nothing

Note

• reflection is not used, so exceptions are thrown directly (i.e. not wrapped as java.lang.reflect.InvocationTargetException objects)
• for static method invocations, this function is identical to invoke()

load_class()

Jni::java::lang::Class Jni::org::qore::jni::load_class

(

string

name

)

Loads a Java class with given name.

Parameters

name	the name of the class to load in internal ("java/lang/String") format

Returns

the loaded class

Exceptions

JNI-ERROR

if the class cannot be loaded

Example:

Class c = Jni::load_class("java/lang/String");

new_array()

Jni::org::qore::jni::JavaArray Jni::org::qore::jni::new_array	(	Jni::java::lang::Class	cls,
		int	size
	)

Allocates a new Java array.

Parameters

cls	the Class of the component type of the Array
size	the size of the array to allocate

Returns

the allocated array

set_save_object_callback()

Jni::org::qore::jni::set_save_object_callback

(

*code

save_object_callback

)

Sets the "save object" callback for Qore objects created from Java code.

Restrictions:

Qore::PO_NO_PROCESS_CONTROL

Example:

hash<string, object> object_cache;
code callback = sub (object obj) {
    # save object in object cache, so it doesn't go out of scope
    object_cache{obj.uniqueHash()} = obj;
}
set_save_object_callback(callback);

Parameters

save_object_callback

the callback to save any Qore objects created in Java code, must take an argument of type object

Due to the differences in garbage collection approaches between Qore and Java, Qore objects must be managed with a deterministic life cycle; Java objects have only weak references to Qore objects due to the lack of destructors in Java and the lack of determinism in the JVM for object lifecycle management.

The callback set here will be called any time a Qore object is created from Java code; if no callback is set, then the standard thread-local implementation is used where Qore objects are saved in a thread-local hash.

See also

Managing the Lifecycle of Qore objects from Java for more information