X-Git-Url: http://nitlanguage.org

diff --git a/lib/java.nit b/lib/java.nit
index 9db363c..de82015 100644
--- a/lib/java.nit
+++ b/lib/java.nit
@@ -15,6 +15,17 @@
 # limitations under the License.
 
 # Supporting services for the FFI with Java
+#
+# This modules relies on `Sys::jvm`, `Sys::jni_env` and
+# `Sys::create_default_jvm` to get a handle on a JVM. You can adapt the
+# behavior of the FFI and services in this module by redefing
+# `Sys::create_default_jvm` and supply your own JVM object. You can manage
+# multiple java thread by switching the current environment in a redef
+# of `Sys::jni_env`, and multiple JVM using `Sys::jvm`.
+#
+# The module `jvm` gives more control over the JVM instances and wraps
+# most of JNI functions. You can use it to further customize the behavior 
+# of your code.
 module java is
 	c_compiler_option("-I $(JAVA_HOME)/include/")
 	c_linker_option("-L $(JNI_LIB_PATH) -ljvm")
@@ -38,7 +49,6 @@ redef class Sys
 	fun jvm=(jvm: JavaVM) do jvm_cache = jvm
 
 	# Current main `JniEnv`
-	# FIXME support threaded Java
 	fun jni_env: JniEnv
 	do
 		if jni_env_cache == null then create_default_jvm
@@ -49,7 +59,7 @@ redef class Sys
 	fun jni_env=(jni_env: JniEnv) do jni_env_cache = jni_env
 
 	# Called by `jvm` and `jni_env` to instanciate a Java Virual Machine.
-	# Used mostly for FFI with Java.
+	# Used mostly for the FFI with Java.
 	protected fun create_default_jvm
 	do
 		var builder = new JavaVMBuilder
@@ -63,4 +73,94 @@ redef class Sys
 		self.jvm = jvm
 		self.jni_env = builder.jni_env.as(not null)
 	end
+
+	# Get a Java class by its name from the current `jni_env`
+	fun load_jclass(name: NativeString): JClass import jni_env `{
+		JNIEnv *nit_ffi_jni_env = Sys_jni_env(recv);
+
+		// retreive the implementation Java class
+		jclass java_class = (*nit_ffi_jni_env)->FindClass(nit_ffi_jni_env, name);
+		if (java_class == NULL) {
+			fprintf(stderr, "Nit FFI with Java error: failed to load class.\\n");
+			(*nit_ffi_jni_env)->ExceptionDescribe(nit_ffi_jni_env);
+			exit(1);
+		}
+
+		return java_class;
+	`}
+end
+
+# A standard Java string `java.lang.String`
+#
+# Converted to a Nit string using `to_s`, or to a C string with `to_cstring`.
+# Created using `String::to_java_string` or `NativeString::to_java_string`.
+extern class JavaString in "Java" `{ java.lang.String `}
+	super JavaObject
+
+	redef type SELF: JavaString
+
+	# Get the string from Java and copy it to Nit memory
+	fun to_cstring: NativeString import sys, Sys.jni_env `{
+		Sys sys = JavaString_sys(recv);
+		JNIEnv *env = Sys_jni_env(sys);
+
+		// Get the data from Java
+		const jbyte *java_cstr = (char*)(*env)->GetStringUTFChars(env, recv, NULL);
+		jsize len = (*env)->GetStringUTFLength(env, recv);
+
+		// Copy it in control of Nit
+		char *nit_cstr = (char*)malloc(len+1);
+		memcpy(nit_cstr, java_cstr, len);
+		nit_cstr[len] = '\0';
+
+		// Free JNI ref and return
+		(*env)->ReleaseStringUTFChars(env, recv, java_cstr);
+		return nit_cstr;
+	`}
+
+	redef fun to_s do return to_cstring.to_s
+end
+
+redef class NativeString
+	# Get a Java string from this C string
+	#
+	# This instance is only valid until the next execution of Java code.
+	# You can use `new_local_ref` to keep it longer.
+	fun to_java_string: JavaString import sys, Sys.jni_env `{
+		Sys sys = JavaString_sys(recv);
+		JNIEnv *env = Sys_jni_env(sys);
+		return (*env)->NewStringUTF(env, recv);
+	`}
+end
+
+redef class String
+	fun to_java_string: JavaString do return to_cstring.to_java_string
+end
+
+redef extern class JavaObject
+	type SELF: JavaObject
+
+	# Returns a global reference to the Java object behind this reference
+	#
+	# You must use a global reference when keeping a Java object
+	# across execution of Java code, per JNI specification.
+	fun new_global_ref: SELF import sys, Sys.jni_env `{
+		Sys sys = JavaObject_sys(recv);
+		JNIEnv *env = Sys_jni_env(sys);
+		return (*env)->NewGlobalRef(env, recv);
+	`}
+
+	# Delete this global reference
+	fun delete_global_ref import sys, Sys.jni_env `{
+		Sys sys = JavaObject_sys(recv);
+		JNIEnv *env = Sys_jni_env(sys);
+		(*env)->DeleteGlobalRef(env, recv);
+	`}
+
+	# Delete this local reference
+	fun delete_local_ref import sys, Sys.jni_env `{
+		Sys sys = JavaObject_sys(recv);
+		JNIEnv *env = Sys_jni_env(sys);
+		(*env)->DeleteLocalRef(env, recv);
+	`}
 end