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miniJVM

Develop iOS Android app in java, Cross platform java virtual machine , the minimal jvm .

Features
Architecture
Build for iOS/Android platform
Build for Windows/Linux/MacOS platform
How to debug source
Using miniJVM in project
Documentation
License

Features

• Jvm Build pass: iOS / Android / mingw-w64 32|64bit / MSVC 32|64bit / MacOS / Linux
• No dependence Library
• Minimal memory footprint
• Minimal binary, embedded jvm
• Minimal bootstrap classlib , So the classes is NOT FULL of jdk 1.8
• Support java source compiler(janino compiler)
• Jit support
• Low latency java garbage collection
• Java remote debug supported, JDWP Spec
• Translate minijvm classes to C source code to improve execute speed.

iOS/Android Platform Extended Features

• OpenGL ES 3.0
• Swing like gui lib, HTML like XML layout
• Audio/Video Playback and Capture
• Take photo from Camera or Album
• Save and Load file from mobile device
• Api compatible with miniJVM desktop platform, app can running on desktop platform

MiniJVM on Web

MiniJVM on web build by Starcommander. Source Web demo

MiniJVM gui Demo

• Instant Message app Demo , Source
• 3D game app Demo, Source

Architecture:

Changelog:

2023.09. Rebound the glfw and glfm graphics jni and separated the GUI java class into the xgui package .
2022.11. Add documentation.
2021.03. Add j2c module, it 's a tool for convert minijvm java source code to c source code , then build it as native application , support desktop and mobile platform .
2020.12. Add build script and release v2.1.
2020.10. Refactor source and remove binary in repository.
2020.10. Https supported.
2020.03. Add xml layout for gui system, add 3D game demo for minijvm, fix jdwp debug for jetbrain idea.
2019.12. Bind cross-platform awtk ui system , see awtk-minijvm
2019.12. Jit enabled, it based on sljit project
2019.10. Jit is developing
2018.12. Optimize performance
2017.09. miniJVM start

Build for iOS/Android platform:

Write java code once , running on all of iOS / Android / MacOSX / Win / Linux platforms
There were not essential jar file pre-built, so build these jar file first
Develop IDE: Eclipse, Netbeans or JetBrains Intelli Idea

1. Run script /binary/build_jar.sh or /binary/build_jar.bat to generted jars.
   Or

   Build maven projects /minijvm/java copy to /mobile/assets/resfiles/minijvm_rt.jar
   Build maven projects /mobile/java/glfm_gui, copy to /mobile/assets/resfiles/glfm_gui.jar
   Build maven projects /mobile/java/ExApp, copy to /mobile/assets/resfiles/ExApp.jar
   Maybe you can change /mobile/java/ExApp/src/main/java/test/MyApp.java , Add your resource to /mobile/java/ExApp/src/main/resource/res/ , such as audio or image etc, Configure /mobile/java/ExApp/src/main/config.txt for icon ,version, boot class, etc

2. XCode open /mobile/iosapp ,setup developer account in Signing&Capabilities , build and install app to Device , verify app before running app (Setting->General->Device Management->{Developer account}->Verify App->Trust)

3. Android Studio open /mobile/androidapp build and install app to Android device

4. The AppManager is running

Build for Windows/Linux/MacOS platform

1. Run script /binary/build_jar.sh or /binary/build_jar.bat to generted jars
   Or

   Build java bootstrap classes /minijvm/java , Maven build jar and copy to /binary/lib/minijvm_rt.jar
   Build gui classes /desktop/glfw_gui/java , Maven build jar and copy to /binary/libex/glfw_gui.jar
   Build console test case classes /test/minijvm_test , Maven build jar and copy to /binary/libex/minijvm_test.jar
   Build gui test app classes /mobile/java/ExApp , Maven built jar and copy to /binary/{platform}/apps/ExApp.jar

2. Run /binary/build_mac_linux.sh or /binary/build_wini686.bat or /binary/build_winx64.bat to generted binaries
   Or

   Build gui jni c dynamic library /desktop/glfw_gui/c by cmake
   Build minijvm /minijvm/c by cmake

3. Run test script /binary/{platform}/test.sh | test.bat

How to debug source

Almost all Java IDEs support remote debugging. The IDE connects to the debug port of the miniJVM through TCP, and then enters the debugging state. The miniJVM has two options, one is to enable the debugging function, and the other is to wait for the IDE to connect to the debug port after the VM is started, and execute the bytecode only after that. These two options need to be setup before initializing the VM.
These two options defined in jvm.h

struct _MiniJVM {
    ...
    s32 jdwp_enable;// 0:disable java debug , 1:enable java debug and disable jit
    s32 jdwp_suspend_on_start;
    ...
};

1. Open miniJVM debug mode, mini_jvm jdwp listen on port 8000
   Desktop platform : Run mini_jvm with flag: -Xdebug for debug mode ,Or change source before build.
   /minijvm/c/main.c 134: jvm->jdwp_enable = 1; //change "jdwp" to 1
   iOS/Android : change source before build
   /mobile/c/glfmapp/main.c 50: refers.jvm->jdwp_enable = 1; //change 0 to 1
   If debug on phone device, check the device ip address from General Setting -> wifi ->(i)

2. Run the VM with jars eg:
   mini_jvm.exe -Xdebug -bootclasspath ../lib/minijvm_rt.jar -cp ../libex/glfw_gui.jar org.mini.glfw.GlfwMain

3. IDE open project , eg: /mobile/java/ExApp
   Intelli idea : menu Run -> Edit Configurations , + remote , Transport : socket , Debugger mode : attach , host is your mini_jvm running on host ip and port ,ex "127.0.0.1:8000" or "192.168.0.32:8000"
   Eclipse : configuration like as idea
   Netbeans : menu Debug -> connect to Debugger, Connector : SocketAttach , host is your mini_jvm running on the host and port, ex. "localhost:8000" , Timeout: 10000

4. Then you can set breakpoints and pause vm and watch variables

Project based miniJVM

Awtk-minijvm :AWTK cross platform native ui bind to minijvm
LWJGUI-Mobile : java LWJGL UI library
BiBiX : java instantial messager
G3d : java 3d game demo
MiniJVM web demo : miniJVM on web demo

miniJVM referenced project and technology

Oracle CLDC :referenced cldc api
OpenJDK : referenced java api
Miniz :for read jar files
Glfm :for cross platform (android/ios) GUI
Nanovg :for GUI paint function
Stb :for GUI truetype font and image
Glad :for replace openGL/GLES head file
Glfw :for pc cross platform GUI
Dirent :for linux style on win vc file and directory access
Tinycthread :for cross platform thread
JRegex :for java String regex match
Janino :for compile java source file
MiniAudio :for java audio playback and capture
Sljit :Platform independent low-level JIT compiler
Mbedtls :Https support by mbedtls
Avian :referenced java api

Development IDE usage

C / ObjC: JetBrains CLion, Xcode, Virtual studio
Swift : XCode
Java : Jetbrain Idea, Netbeans
Android : Android Studio

Using miniJVM in project

Copy C source /minijvm/c to your project source folder, copy built jar minijvm_rt.jar to you projec resource folder

#include "jvm/jvm.h"

int main(int argc, char **argv) {
    char *bootclasspath = "../../binary/lib/minijvm_rt.jar";
    char *classpath = "../../binary/libex/minijvm_test.jar;./";
    char *main_name = "test.Foo3";

    s32 ret = 1;
    MiniJVM *jvm = jvm_create();
    if (jvm != NULL) {
        jvm->jdwp_enable = 0; //value 1 for java remote debug enable
        jvm->jdwp_suspend_on_start = 0;
        jvm->max_heap_size = 25 * 1024 * 1024; //

        ret = jvm_init(jvm, bootclasspath, classpath);
        if (ret) {
            printf("[ERROR]minijvm init error.\n");
        } else {
            ret = call_main(jvm, main_name, NULL);
        }
        jvm_destroy(jvm);
    }
    return ret;
}

Third liberies

• Janino java compiler

Project: Janino
Janino is a super-small, super-fast Java compiler.
Janino can not only compile a set of source files to a set of class files like JAVAC, but also compile a Java expression, a block, a class body, one .java file or a set of .java files in memory, load the bytecode and execute it directly in the same JVM. Janino compiler is not the full java compiler, see limitation , like :

List<String> list=new ArrayList();
list.add("abc");
String s=(String)list.get(0);//can't ignore (String) cast qualifier.

Download jars :
janino.jar
commons-compiler.jar

#compile /binary/res/BpDeepTest.java
mini_jvm -bootclasspath ../lib/minijvm_rt.jar -cp ../libex/janino.jar:../libex/commons-compiler.jar   org.codehaus.janino.Compiler  ../res/BpDeepTest.java

• Luaj

Project: Luaj
miniJVM adapted : [Luaj minijvm] https://github.com/digitalgust/minijvm_third_lib Lightweight, fast, Java-centric Lua interpreter written for JME and JSE, with string, table, package, math, io, os, debug, coroutine & luajava libraries, JSR-223 bindings, all metatags, weak tables and unique direct lua-to-java-bytecode compiling. Download jars :
luaj.jar

mini_jvm -bootclasspath ../lib/minijvm_rt.jar -cp ../libex/luaj.jar Sample

Screen shot

Directorie struct

.
├── binary              miniJVM binary  for build(win32/win64/mac/linux/
├── desktop
│   ├── awtk_gui        open source gui frame awtk jni
│   └── glfw_gui        desktop openGL, glfw, miniaudio, native module
├── j2c                 miniJVM java source translate to c tools
│   ├── app
│   └── translator
├── minijvm             Core source
│   ├── c               miniJVM c source 
│   └── java            miniJVM runtime library
├── mobile
│   ├── androidapp      Android launcher
│   ├── assets          mobile app resource, font files, jar files ,pic ,audio etc.
│   ├── c               mobile native lib, openGLES, glfm framework, gui jni, glfmapp
│   ├── iosapp          iOS launcher
│   └── java            mobile java lib, GUI, AppManager, app example
├── doc
└── test                miniJVM test case 

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License

License: MIT

Gust , digitalgust@163.com .