Bcel version problem when using LuaJC in multi Thread #85

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open-autonomous-connection · 2021-03-25T08:50:28Z

lewy95 commented

2021-03-25 08:50:28 +00:00

(Migrated from github.com)

I tried to use LuaJC in the situation of multi thread but got failed.

Problems

I used the official case referring to http://www.luaj.org/luaj/3.0/examples/jse/SampleMultiThreaded.java, and I just added one line code 'LuaJC.install(g);' after the initialization of Globals，just like the code below.

public void run() {
    try {
        // Each thread must have its own Globals.
        Globals g = JsePlatform.standardGlobals();
        LuaJC.install(g);
        // Once a Globals is created, it can and should be reused
        // within the same thread.
        g.loadfile(script1).call();
        // g.loadfile(script2).call();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

But the result is always wrong with Exception:

Exception in thread "Runner-0" java.lang.ClassFormatError: Invalid length 65535 in LocalVariableTable in class file lua_hello$sayHello at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:763) at java.lang.ClassLoader.defineClass(ClassLoader.java:642) at org.luaj.vm2.luajc.JavaLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:2671) at java.lang.Class.getConstructor0(Class.java:3075) at java.lang.Class.newInstance(Class.java:412) at org.luaj.vm2.luajc.JavaLoader.load(Unknown Source) at org.luaj.vm2.luajc.JavaLoader.load(Unknown Source) at org.luaj.vm2.luajc.JavaLoader.load(Unknown Source) at org.luaj.vm2.luajc.LuaJC.load(Unknown Source) at org.luaj.vm2.Globals.load(Unknown Source) at org.luaj.vm2.Globals.loadfile(Unknown Source) at cn.xzxy.lewy.luaj.SampleMultiThreaded$Runner.run(SampleMultiThreaded.java:40) at java.lang.Thread.run(Thread.java:748)

So，I gusse there is a problem when bcel complies the same lua file in multi thread situation.

Solutions

After tough attempts，I find two solutions.

move the code into main thread jusy like this

static class Runner implements Runnable {
        final String script;
        LuaValue luaValue;

        Runner(String script) {
            Globals g = JsePlatform.standardGlobals();
            LuaJC.install(g);
            luaValue = g.loadfile(script);
            this.script = script;
        }

        public void run() {
            try {
                luaValue.call();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

replace the bcel 5.2 with bcel 6.5.0

<dependency>
    <groupId>org.apache.bcel</groupId>
    <artifactId>bcel</artifactId>
    <version>6.5.0</version>
</dependency>

Conclusion

According to the introduction of official website, the bcel-5.2.jar is the first we know.

java -cp "lib/luaj-jse-3.0.1.jar;lib/bcel-5.2.jar" lua -b examples/lua/hello.lua

But bcel-5.2.jar can only work when we use LuaJC in single thread situation. We should use the version of 6.5.0 to deal with multi thread.

Finally，LuaJC is indeed the better way that java program calls lua script.

I tried to use LuaJC in the situation of multi thread but got failed. ### Problems I used the official case referring to http://www.luaj.org/luaj/3.0/examples/jse/SampleMultiThreaded.java, and I just added one line code 'LuaJC.install(g);' after the initialization of Globals，just like the code below. ``` public void run() { try { // Each thread must have its own Globals. Globals g = JsePlatform.standardGlobals(); LuaJC.install(g); // Once a Globals is created, it can and should be reused // within the same thread. g.loadfile(script1).call(); // g.loadfile(script2).call(); } catch (Exception e) { e.printStackTrace(); } } ``` But the result is always wrong with Exception: `Exception in thread "Runner-0" java.lang.ClassFormatError: Invalid length 65535 in LocalVariableTable in class file lua_hello$sayHello at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:763) at java.lang.ClassLoader.defineClass(ClassLoader.java:642) at org.luaj.vm2.luajc.JavaLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at java.lang.ClassLoader.loadClass(ClassLoader.java:357) at java.lang.Class.getDeclaredConstructors0(Native Method) at java.lang.Class.privateGetDeclaredConstructors(Class.java:2671) at java.lang.Class.getConstructor0(Class.java:3075) at java.lang.Class.newInstance(Class.java:412) at org.luaj.vm2.luajc.JavaLoader.load(Unknown Source) at org.luaj.vm2.luajc.JavaLoader.load(Unknown Source) at org.luaj.vm2.luajc.JavaLoader.load(Unknown Source) at org.luaj.vm2.luajc.LuaJC.load(Unknown Source) at org.luaj.vm2.Globals.load(Unknown Source) at org.luaj.vm2.Globals.loadfile(Unknown Source) at cn.xzxy.lewy.luaj.SampleMultiThreaded$Runner.run(SampleMultiThreaded.java:40) at java.lang.Thread.run(Thread.java:748)` So，I gusse there is a problem when bcel complies the same lua file in multi thread situation. ### Solutions After tough attempts，I find two solutions. 1. move the code into main thread jusy like this ``` static class Runner implements Runnable { final String script; LuaValue luaValue; Runner(String script) { Globals g = JsePlatform.standardGlobals(); LuaJC.install(g); luaValue = g.loadfile(script); this.script = script; } public void run() { try { luaValue.call(); } catch (Exception e) { e.printStackTrace(); } } } ``` 2. replace the bcel 5.2 with bcel 6.5.0 ``` <dependency> <groupId>org.apache.bcel</groupId> <artifactId>bcel</artifactId> <version>6.5.0</version> </dependency> ``` ### Conclusion According to the introduction of official website, the bcel-5.2.jar is the first we know. `java -cp "lib/luaj-jse-3.0.1.jar;lib/bcel-5.2.jar" lua -b examples/lua/hello.lua` But bcel-5.2.jar can only work when we use LuaJC in single thread situation. We should use the version of `6.5.0` to deal with multi thread. Finally，LuaJC is indeed the better way that java program calls lua script.

open-autonomous-connection commented

2026-03-01 18:01:24 +00:00

We updated bcel

open-autonomous-connection closed this issue

2026-03-01 18:01:24 +00:00

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Reference: open-autonomous-connection/luaj#85