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开源软件名称（OpenSource Name）：darmie/LuaJ开源软件地址(OpenSource Url)：https://github.com/darmie/LuaJ开源编程语言(OpenSource Language)：Java 91.4%开源软件介绍(OpenSource Introduction)：
#Getting Started with LuaJ. James Roseborough, Ian Farmer, Version 3.0 Copyright © 2009-2014 Luaj.org. (Also Nathan, Marcus, and Pratik for the crazy hack job with the chainsaw that makes it make it through proguard on Android without warnings.) Freely available under the terms of the Luaj license. introduction · examples · concepts · libraries · luaj api · parser · building · downloads · release notes 1 - IntroductionGoals of LuajLuaj is a lua interpreter based on the 5.2.x version of lua with the following goals in mind:
Luaj version and Lua VersionsLuaj 3.0.xSupport for lua 5.2.x features:
It also includes miscellaneous improvements over luaj 2.0.x:
Luaj 2.0.xSupport for lua 5.1.x features, plus:
Luaj 1.0.xSupport for most lua 5.1.x features. PerformanceGood performance is a major goal of luaj. The following table provides measured execution times on a subset of benchmarks from the computer language benchmarks game in comparison with the standard C distribution.
Luaj in interpreted mode performs well for the benchmarks, and even better when the lua-to-java-bytecode (luajc) compiler is used, and actually executes faster than C-based lua in some cases. It is also faster than Java-lua implementations Jill, Kahlua, and Mochalua for all benchmarks tested. 2 - ExamplesRun a lua script in Java SEFrom the main distribution directory line type: java -cp lib/luaj-jse-3.0.jar lua examples/lua/hello.lua You should see the following output: hello, world To see how luaj can be used to acccess most Java API's including swing, try: java -cp lib/luaj-jse-3.0.jar lua examples/lua/swingapp.lua Links to sources: examples/lua/hello.lua examples/lua/swingapp.lua Compile lua source to lua bytecodeFrom the main distribution directory line type: java -cp lib/luaj-jse-3.0.jar luac examples/lua/hello.lua java -cp lib/luaj-jse-3.0.jar lua luac.out The compiled output "luac.out" is lua bytecode and should run and produce the same result. Compile lua source or bytecode to java bytecodeLuaj can compile lua sources or binaries directly to java bytecode if the bcel library is on the class path. From the main distribution directory line type: ant bcel-lib java -cp "lib/luaj-jse-3.0.jar;lib/bcel-5.2.jar" luajc -s examples/lua -d . hello.lua java -cp "lib/luaj-jse-3.0.jar;." lua -l hello The output hello.class is Java bytecode, should run and produce the same result. There is no runtime dependency on the bcel library, but the compiled classes must be in the class path at runtime, unless runtime jit-compiling via luajc and bcel are desired (see later sections). Lua scripts can also be run directly in this mode without precompiling using the lua command with the -b option and providing the bcel library in the class path: java -cp "lib/luaj-jse-3.0.jar;lib/bcel-5.2.jar" lua -b examples/lua/hello.lua Run a script in a Java ApplicationA simple hello, world example in luaj is: import org.luaj.vm2.*;
import org.luaj.vm2.lib.jse.*;
Globals globals = JsePlatform.standardGlobals();
LuaValue chunk = globals.load("print 'hello, world'");
chunk.call();Loading from a file is done via Globals.loadFile(): LuaValue chunk = globals.loadfile("examples/lua/hello.lua");Chunks can also be loaded from a chunk = globals.load(new StringReader("print 'hello, world'"), "main.lua");or an InputStream to be loaded as text source "t", or binary lua file "b": chunk = globals.load(new FileInputSStream("examples/lua/hello.lua"), "main.lua", "bt"));
A simple example may be found in examples/jse/SampleJseMain.java You must include the library lib/luaj-jse-3.0.jar in your class path. Run a script in a MIDletFor MIDlets the JmePlatform is used instead: import org.luaj.vm2.*;
import org.luaj.vm2.lib.jme.*;
Globals globals = JmePlatform.standardGlobals();
LuaValue chunk = globals.loadfile("examples/lua/hello.lua");
chunk.call();The file must be a resource within within the midlet jar for the loader to find it. Any files included via require() must also be part of the midlet resources. A simple example may be found in examples/jme/SampleMIDlet.java You must include the library lib/luaj-jme-3.0.jar in your midlet jar. An ant script to build and run the midlet is in build-midlet.xml You must install the wireless toolkit and define WTK_HOME for this script to work. Run a script using JSR-223 Dynamic ScriptingThe standard use of JSR-223 scripting engines may be used: ScriptEngineManager mgr = new ScriptEngineManager();
ScriptEngine e = mgr.getEngineByName("luaj");
e.put("x", 25);
e.eval("y = math.sqrt(x)");
System.out.println( "y="+e.get("y") );You can also look up the engine by language "lua" or mimetypes "text/lua" or "application/lua". All standard aspects of script engines including compiled statements are supported. You must include the library lib/luaj-jse-3.0.jar in your class path. A working example may be found in examples/jse/ScriptEngineSample.java To compile and run it using Java 1.6 or higher: javac -cp lib/luaj-jse-3.0.jar examples/jse/ScriptEngineSample.java java -cp "lib/luaj-jse-3.0.jar;examples/jse" ScriptEngineSample Excluding the lua bytecode compilerBy default, the compiler is included whenever standardGlobals() or debugGlobals() are called. Without a compiler, files can still be executed, but they must be compiled elsewhere beforehand. The "luac" utility is provided in the jse jar for this purpose, or a standard lua compiler can be used. To exclude the lua-to-lua-bytecode compiler, do not call standardGlobals() or debugGlobals() but instead initialize globals with including only those libraries that are needed and omitting the line: org.luaj.vm2.compiler.LuaC.install(globals); Including the LuaJC lua-bytecode-to-Java-bytecode compilerTo compile from lua to Java bytecode for all lua loaded at runtime, install the LuaJC compiler into a globals object use: org.luaj.vm2.jse.luajc.LuaJC.install(globals); This will compile all lua bytecode into Java bytecode, regardless of if they are loaded as lua source or lua binary files. The requires bcel to be on the class path, and the ClassLoader of JSE or CDC. 3 - ConceptsGlobalsThe old notion of platform has been replaced with creation of globals. The Globals class holds global state needed for executing closures as well as providing convenience functions for compiling and loading scripts. PlatformTo simplify construction of Globals, and encapsulate differences needed to support the diverse family of Java runtimes, luaj uses a Platform notion. Typically, a platform is used to construct a Globals, which is then provided as a global environment for client scripts. JsePlatformThe JsePlatform class can be used as a factory for globals in a typical Java SE application. All standard libraries are included, as well as the luajava library. The default search path is the current directory, and the math operations include all those supported by Java SE. AndroidAndroid applications should use the JsePlatform, and can include the Luajava library to simplify access to underlying Android APIs. A specialized Globals.finder should be provided to find scripts and data for loading. See examples/android/src/android/LuajView for an example that loads from the "res" Android project directory. The ant build script is examples/android/build.xml. AppletApplets in browsers should use the JsePlatform. The permissions model in applets is highly restrictive, so a specialization of the Luajava library must be used that uses default class loading. This is illustrated in the sample Applet examples/jse/SampleApplet.java, which can be built using build-applet.xml. JmePlatformThe JmePlatform class can be used to set up the basic environment for a Java ME application. The default search path is limited to the jar resources, and the math operations are limited to those supported by Java ME. All libraries are included except luajava, and the os, io, and math libraries are limited to those functions that can be supported on that platform. MIDletMIDlets require the JmePlatform. The JME platform has several limitations which carry over to luaj. In particular Globals.finder is overridden to load as resources, so scripts should be colocated with class files in the MIDlet jar file. Luajava cannot be used. Camples code is in examples/jme/SampleMIDlet.java, which can be built using build-midlet.xml. Thread SafetyLuaj 3.0 can be run in multiple threads, with the following restrictions:
For an example of loading allocating per-thread Globals and invoking scripts in multiple threads see examples/jse/SampleMultiThreaded.java As an alternative, the JSR-223 scripting interface can be used, and should always provide a separate Globals instance per script engine instance by using a ThreadLocal internally. 4 - LibrariesStandard LibrariesLibraries are coded to closely match the behavior specified in See standard lua documentation for details on the library API's The following libraries are loaded by both JsePlatform.standardGlobals() and JmePlatform.standardGlobals(): base bit32 coroutine io math os package string table The JsePlatform.standardGlobals() globals also include: luajava The JsePlatform.debugGlobals() and JsePlatform.debugGlobals() functions produce globals that include: debug I/O LibraryThe implementation of the io library differs by platform owing to platform limitations. The JmePlatform.standardGlobals() instantiated the io library io in src/jme/org/luaj/vm2/lib/jme/JmeIoLib.java The JsePlatform.standardGlobals() includes support for random access and is in src/jse/org/luaj/vm2/lib/jse/JseIoLib.java OS LibraryThe implementation of the os library also differs per platform. The basic os library implementation us used by JmePlatform and is in: src/core/org/luaj/lib/OsLib.java A richer version for use by JsePlatform is : src/jse/org/luaj/vm2/lib/jse/JseOsLib.java Time is a represented as number of seconds since the epoch, and locales are not implemented. Coroutine LibraryThe coroutine library is implemented using one JavaThread per coroutine. This allows coroutine.yield() can be called from anywhere, as with the yield-from-anywhere patch in C-based lua. Luaj uses WeakReferences and the OrphanedThread error to ensure that coroutines that are no longer referenced are properly garbage collected. For thread safety, OrphanedThread should not be caught by Java code. See LuaThread and OrphanedThread javadoc for details. Debug LibraryThe debug library is not included by default by JmePlatform.standardGlobals() or JsePlatform.standardGlobsls() . The functions JmePlatform.debugGlobals() and JsePlatform.debugGlobsls() create globals that contain the debug library in addition to the other standard libraries. To install dynamically from lua use java-class-based require:: require 'org.luaj.vm2.lib.DebugLib'The lua command line utility includes the debug library by default. The Luajava LibraryThe JsePlatform.standardGlobals() includes the luajava library, which simplifies binding to Java classes and methods. It is patterned after the original luajava project. The following lua script will open a swing frame on Java SE: jframe = luajava.bindClass( "javax.swing.JFrame" )
frame = luajava.newInstance( "javax.swing.JFrame", "Texts" );
frame:setDefaultCloseOperation(jframe.EXIT_ON_CLOSE)
frame:setSize(300,400)
frame:setVisible(true)See a longer sample in examples/lua/swingapp.lua for details, including a simple animation loop, rendering graphics, mouse and key handling, and image loading. Or try running it using: java -cp lib/luaj-jse-3.0.jar lua examples/lua/swingapp.lua The Java ME platform does not include this library, and it cannot be made to work because of the lack of a reflection API in Java ME. The lua connand line tool includes luajava. 5 - LuaJ APIAPI JavadocThe javadoc for the main classes in the LuaJ API are on line at docs/api You can also build a local version from sources using ant doc LuaValue and VarargsAll lua value manipulation is now organized around LuaValue which exposes the majority of interfaces used for lua computation. org.luaj.vm2.LuaValue Common FunctionsLuaValue exposes functions for each of the operations in LuaJ. Some commonly used functions and constants include: call(); // invoke the function with no arguments
call(LuaValue arg1); // call the function with 1 argument
invoke(Varargs arg); // call the function with variable arguments, variable return values
get(int index); // get a table entry using an integer key
get(LuaValue key); // get a table entry using an arbitrary key, may be a LuaInteger
rawget(int index); // raw get without metatable calls
valueOf(int i); // return LuaValue corresponding to an integer
valueOf(String s); // return LuaValue corresponding to a String
toint(); // return value as a Java int
tojstring(); // return value as a Java String
isnil(); // is the value nil
NIL; // the value nil
NONE; // a Varargs instance with no values VarargsThe interface Varargs provides an abstraction for both a variable argument list and multiple return values. For convenience, LuaValue implements Varargs so a single value can be supplied anywhere variable arguments are expected. org.luaj.vm2.Varargs Common FunctionsVarargs exposes functions for accessing elements, and coercing them to specific types: narg(); // return number of arguments
arg1(); // return the first argument
arg(int n); // return the nth argument
isnil(int n); // true if the nth argument is nil
checktable(int n); // return table or throw error
optlong(int n,long d); // return n if a long, d if no argument, or error if not a longSee the Varargs API for a complete list. LibFunctionThe simplest way to implement a function is to choose a base class based on the number of arguments to the function. LuaJ provides 5 base classes for this purpose, depending if the function has 0, 1, 2, 3 or variable arguments, and if it provide multiple return values. org.luaj.vm2.lib.ZeroArgFunction, org.luaj.vm2.lib.OneArgFunction, org.luaj.vm2.lib.TwoArgFunction, org.luaj.vm2.lib.ThreeArgFunction, org.luaj.vm2.lib.VarArgFunction Each of these functions has an abstract method that must be implemented, and argument fixup is done automatically by the classes as each Java function is invoked. An example of a function with no arguments but a useful return value might be: pubic class hostname extends ZeroArgFunction {
public LuaValue call() {
return valueOf(java.net.InetAddress.getLocalHost().getHostName());
}
}The value env is the environment of the function, and is normally supplied by the instantiating object whenever default loading is used. Calling this function from lua could be done by: local hostname = require( 'hostname' )while calling this function from Java would look like: new hostname().call();Note that in both the lua and Java case, extra arguments will be ignored, and the function will be called. Also, no virtual machine instance is necessary to call the function. To allow for arguments, or return multiple values, extend one of the other base classes. Libraries of Java FunctionsWhen require() is called, it will first attempt to load the module as a Java class that implements LuaFunction. To succeed, the following requirements must be met:
If luaj can find a class that meets these critera, it will instantiate it, cast it to LuaFunction then call() the instance with two arguments: the modname used in the call to require(), and the environment for that function. The Java may use these values however it wishes. A typical case is to create named functions in the environment that can be called from lua. A complete example of Java code for a simple toy library is in examples/jse/hyperbolic.java import org.luaj.vm2.LuaValue;
import org.luaj.vm2.lib.*;
public class hyperbolic extends TwoArgFunction {
public hyperbolic() {}
public LuaValue call(LuaValue modname, LuaValue env) {
LuaValue library = tableOf();
library.set( "sinh", new sinh() );
library.set( "cosh", new cosh() );
env.set( "hyperbolic", library );
return library;
}
static class sinh extends OneArgFunction {
public LuaValue call(LuaValue x) {
return LuaValue.valueOf(Math.sinh(x.checkdouble()));
}
}
static class cosh extends OneArgFunction {
public LuaValue call(LuaValue x) {
return LuaValue.valueOf(Math.cosh(x.checkdouble()));
}
}
}In this case the call to require invokes the library itself to initialize it. The library implementation puts entries into a table, and stores this table in the environment. The lua script used to load and test it is in examples/lua/hyperbolicapp.lua require 'hyperbolic'
print('hyperbolic', hyperbolic)
print('hyperbolic.sinh', hyperbolic.sinh)
print('hyperbolic.cosh', hyperbolic.cosh)
print('sinh(0.5)', hyperbolic.sinh(0.5))
print('cosh(0.5)', hyperbolic.cosh(0.5))For this example to work the code in hyperbolic.java must be compiled and put on the class path. |
