1 # This file is part of NIT ( http://www.nitlanguage.org ).
3 # Copyright 2014 Alexis Laferrière <alexis.laf@xymus.net>
5 # Licensed under the Apache License, Version 2.0 (the "License");
6 # you may not use this file except in compliance with the License.
7 # You may obtain a copy of the License at
9 # http://www.apache.org/licenses/LICENSE-2.0
11 # Unless required by applicable law or agreed to in writing, software
12 # distributed under the License is distributed on an "AS IS" BASIS,
13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 # See the License for the specific language governing permissions and
15 # limitations under the License.
17 # Supporting services for the FFI with Java
19 # This modules relies on `Sys::jvm`, `Sys::jni_env` and
20 # `Sys::create_default_jvm` to get a handle on a JVM. You can adapt the
21 # behavior of the FFI and services in this module by redefing
22 # `Sys::create_default_jvm` and supply your own JVM object. You can manage
23 # multiple java thread by switching the current environment in a redef
24 # of `Sys::jni_env`, and multiple JVM using `Sys::jvm`.
26 # The module `jvm` gives more control over the JVM instances and wraps
27 # most of JNI functions. You can use it to further customize the behavior
30 c_compiler_option
("-I $(JAVA_HOME)/include/")
31 c_linker_option
("-L $(JNI_LIB_PATH) -ljvm")
37 private var jvm_cache
: nullable JavaVM = null
38 private var jni_env_cache
: nullable JniEnv = null
40 # Default Java Virtual Machine to use (will be instanciated using
41 # `create_default_jvm` if not already set)
44 if jvm_cache
== null then create_default_jvm
45 return jvm_cache
.as(not null)
48 # Sets the current default Java Virtual Machine (use with `jni_env=`)
49 fun jvm
=(jvm
: JavaVM) do jvm_cache
= jvm
51 # Current main `JniEnv`
54 if jni_env_cache
== null then create_default_jvm
55 return jni_env_cache
.as(not null)
58 # Sets the current default JNI env (use with `jvm=`)
59 fun jni_env
=(jni_env
: JniEnv) do jni_env_cache
= jni_env
61 # Called by `jvm` and `jni_env` to instanciate a Java Virual Machine.
62 # Used mostly for the FFI with Java.
63 protected fun create_default_jvm
65 var builder
= new JavaVMBuilder
67 # By default, look for Java classes in a jar file the same dir as the executable
68 builder
.options
.add
"-Djava.class.path={sys.program_name}.jar"
70 var jvm
= builder
.create_jvm
71 assert jvm
!= null else print
"JVM creation failed"
74 self.jni_env
= builder
.jni_env
.as(not null)
77 # Get a Java class by its name from the current `jni_env`
78 fun load_jclass
(name
: NativeString): JClass import jni_env
`{
79 JNIEnv *nit_ffi_jni_env = Sys_jni_env(recv);
81 // retreive the implementation Java class
82 jclass java_class = (*nit_ffi_jni_env)->FindClass(nit_ffi_jni_env, name);
83 if (java_class == NULL) {
84 fprintf(stderr, "Nit FFI with Java error: failed to load class.\\n");
85 (*nit_ffi_jni_env)->ExceptionDescribe(nit_ffi_jni_env);
93 # A standard Java string `java.lang.String`
95 # Converted to a Nit string using `to_s`, or to a C string with `to_cstring`.
96 # Created using `String::to_java_string` or `NativeString::to_java_string`.
97 extern class JavaString in "Java" `{ java.lang.String `}
100 redef type SELF: JavaString
102 # Get the string from Java and copy it to Nit memory
103 fun to_cstring: NativeString import sys, Sys.jni_env `{
104 Sys sys
= JavaString_sys(recv
);
105 JNIEnv *env
= Sys_jni_env(sys
);
107 // Get the data from
Java
108 const jbyte
*java_cstr
= (char
*)(*env
)->GetStringUTFChars(env
, recv
, NULL);
109 jsize len
= (*env
)->GetStringUTFLength(env
, recv
);
111 // Copy it
in control of
Nit
112 char
*nit_cstr
= (char
*)malloc
(len
+1);
113 memcpy
(nit_cstr
, java_cstr
, len
);
114 nit_cstr
[len
] = '\0';
116 // Free JNI ref
and return
117 (*env
)->ReleaseStringUTFChars(env
, recv
, java_cstr
);
121 redef fun to_s do return to_cstring.to_s
124 redef class NativeString
125 # Get a Java string from this C string
127 # This instance is only valid until the next execution of Java code.
128 # You can use `new_local_ref
` to keep it longer.
129 fun to_java_string: JavaString import sys, Sys.jni_env `{
130 Sys sys
= JavaString_sys(recv
);
131 JNIEnv *env
= Sys_jni_env(sys
);
132 return (*env
)->NewStringUTF(env
, recv
);
137 fun to_java_string: JavaString do return to_cstring.to_java_string
140 redef extern class JavaObject
141 type SELF: JavaObject
143 # Returns a global reference to the Java object behind this reference
145 # You must use a global reference when keeping a Java object
146 # across execution of Java code, per JNI specification.
147 fun new_global_ref: SELF import sys, Sys.jni_env `{
148 Sys sys
= JavaObject_sys(recv
);
149 JNIEnv *env
= Sys_jni_env(sys
);
150 return (*env
)->NewGlobalRef(env
, recv
);
153 # Delete this global reference
154 fun delete_global_ref import sys, Sys.jni_env `{
155 Sys sys
= JavaObject_sys(recv
);
156 JNIEnv *env
= Sys_jni_env(sys
);
157 (*env
)->DeleteGlobalRef(env
, recv
);
160 # Delete this local reference
161 fun delete_local_ref import sys, Sys.jni_env `{
162 Sys sys
= JavaObject_sys(recv
);
163 JNIEnv *env
= Sys_jni_env(sys
);
164 (*env
)->DeleteLocalRef(env
, recv
);
167 # Pops the current local reference frame and return a valid reference to self
169 # Similiar to `JavaVM::pop_local_frame
` but returns a value.
170 fun pop_from_local_frame: SELF
172 var jni_env = sys.jni_env
173 return pop_from_local_frame_with_env(jni_env)
176 private fun pop_from_local_frame_with_env(jni_env: JniEnv): SELF `{
177 return (*jni_env
)->PopLocalFrame(jni_env
, recv
);