BoxLang Runtime Architecture

Overview

BoxLang is a dynamic JVM language (JRE 21+) that compiles source to Java bytecode at runtime. The central singleton BoxRuntime acts as a service locator providing access to all core services. Understanding the architecture is essential for building modules, BIFs, interceptors, and custom language extensions.

BoxRuntime — The Central Singleton

import ortus.boxlang.runtime.BoxRuntime;

// Get the singleton instance
BoxRuntime runtime = BoxRuntime.getInstance();

// Start programmatically (e.g., in tests or embedding scenarios)
BoxRuntime runtime = BoxRuntime.getInstance( true );  // true = start immediately

// Core service accessors
runtime.getInterceptorService()    // Event system
runtime.getModuleService()         // Module management
runtime.getCacheService()          // Cache providers
runtime.getAsyncService()          // Executors, futures
runtime.getSchedulerService()      // Cron scheduling
runtime.getDataSourceService()     // JDBC connections
runtime.getFunctionService()       // BIF registry
runtime.getComponentService()      // Component/tag registry
runtime.getClassLocator()          // Class resolution
runtime.getConfiguration()         // Runtime config
runtime.getTypeService()           // Type system

Key Services

InterceptorService

Manages the global event bus. See interceptors skill for full details.

InterceptorService svc = runtime.getInterceptorService();
svc.announce( Key.of("myEvent"), dataStruct );
svc.register( myInterceptor );
svc.unregister( myInterceptor );

ModuleService

ModuleService moduleSvc = runtime.getModuleService();

// Check if a module is loaded
boolean loaded = moduleSvc.hasModule( Key.of("bx-redis") );

// Get module record
ModuleRecord record = moduleSvc.getModuleRecord( Key.of("bx-redis") );
String version = record.version;
String physPath = record.physicalPath;
IStruct settings = record.settings;

// List all loaded modules
Set<Key> modules = moduleSvc.getLoadedModules();

FunctionService (BIF Registry)

FunctionService fnSvc = runtime.getFunctionService();

// Register a custom BIF at runtime
fnSvc.registerGlobalFunction( Key.of("myBif"), new MyBIF() );

// Check if a BIF exists
boolean exists = fnSvc.hasGlobalFunction( Key.of("len") );

// Get a BIF instance
BIF len = fnSvc.getGlobalFunction( Key.of("len") );

AsyncService

AsyncService asyncSvc = runtime.getAsyncService();

// Create a named executor
IBoxExecutor executor = asyncSvc.newExecutor( "myPool", ExecutorType.FIXED, 4 );

// Get an existing executor
IBoxExecutor exec = asyncSvc.getExecutor( "boxlang-tasks" );

// Create a future
BoxFuture<Object> future = asyncSvc.newFuture( () -> expensiveWork() );

IBoxContext — Execution Context Hierarchy

Every BoxLang execution has a context. Contexts form a linked chain for scope resolution.

BoxRuntime
  └── ScriptingRequestBoxContext     (CLI / script execution)
      └── FunctionBoxContext         (inside a function call)
          └── ClosureBoxContext      (inside a closure)
              └── LambdaBoxContext   (inside a lambda)

  └── WebRequestBoxContext           (HTTP request)
      └── ApplicationBoxContext      (Application.bx scope)
          └── SessionBoxContext      (Session scope)
              └── FunctionBoxContext

import ortus.boxlang.runtime.context.IBoxContext;
import ortus.boxlang.runtime.context.FunctionBoxContext;
import ortus.boxlang.runtime.context.ScriptingRequestBoxContext;

// Traverse parent contexts
IBoxContext current = context;
while ( current != null ) {
    System.out.println( current.getClass().getSimpleName() );
    current = current.getParent();
}

// Find a scope nearby (walks up the context chain)
IScope localScope   = context.getScopeNearby( LocalScope.name );
IScope sessionScope = context.getScopeNearby( SessionScope.name );

// Resolve a variable (checks all scopes in order)
ScopeSearchResult result = context.scopeFindNearby( Key.of("myVar"), null );
if ( result != null ) {
    Object value = result.value();
    IScope foundIn = result.scope();
}

// Invoke a BIF from Java code
Object result = context.invokeFunction( Key.of("len"), new Object[]{ "hello" } );

Scope Chain Resolution Order

When BoxLang resolves an unqualified variable name, it searches these scopes in order:

1. local — declared with var in current function
2. arguments — function parameters
3. variables — class/component private scope
4. Named scopes: url, form, cgi, cookie
5. request — per-request shared scope
6. session — user session
7. application — application-wide
8. server — server-wide

DynamicObject — BoxLang's Java Object Wrapper

DynamicObject wraps Java objects and provides BoxLang-style method invocation:

import ortus.boxlang.runtime.dynamic.DynamicObject;

// Wrap any Java object
DynamicObject wrapped = DynamicObject.of( new java.util.ArrayList() );

// Invoke methods
wrapped.invoke( context, "add", new Object[]{ "item" } );
Object size = wrapped.invoke( context, "size", new Object[]{} );

// Get/set fields
Object field = wrapped.getField( Key.of("fieldName") );
wrapped.setField( Key.of("fieldName"), value );

IBoxType — BoxLang Native Types

All BoxLang values implement IBoxType:

import ortus.boxlang.runtime.types.*;
import ortus.boxlang.runtime.types.IType;

// Core type classes
BoxArray   bxArray  = new BoxArray();            // Array
BoxStruct  bxStruct = BoxStruct.of("k","v");     // Struct
BoxString  bxStr    = BoxString.of("hello");     // String (immutable)
BoxInteger bxInt    = BoxInteger.of(42);         // Integer
BoxDouble  bxDbl    = BoxDouble.of(3.14);        // Double
BoxBoolean bxBool   = BoxBoolean.of(true);       // Boolean
BoxNull    bxNull   = BoxNull.INSTANCE;          // Null singleton

// Check type
if ( value instanceof BoxArray arr ) {
    // work with array
}
if ( value instanceof IStruct struct ) {
    // work with struct
}

// Key — interned string for scope/struct access
Key nameKey = Key.of("name");     // interned (fast equality)
Key idKey   = Key.of("id");

Parsing Pipeline

Source code → AST → Java Bytecode:

Source (.bx / .bxs / .bxm / .cfm / .cfc)
    │
    ▼
Lexer (ANTLR4)          → Token stream
    │
    ▼
Parser (ANTLR4)         → Parse tree
    │
    ▼
AST Builder             → BoxLang AST (BoxNode tree)
    │
    ▼
Transpiler/Transformer  → Java AST (JavaParser)
    │
    ▼
Java Compiler           → Java bytecode (.class)
    │
    ▼
ClassLoader             → Loaded & executed by JVM

Debug the AST

# Print the AST for a file
boxlang --bx-printast myScript.bxs

# Print AST from stdin
echo 'var x = 1 + 2' | boxlang --bx-printast -

# Print AST with file path context
boxlang --bx-printast /path/to/file.bxs

Compiled Class Caching

Once compiled, the generated .class files are cached by the ClassLoader. Re-compilation only happens when the source timestamp changes or when reloadOnChange=true is configured.

ClassLoader Isolation

Each module gets its own isolated ClassLoader for the libs/ directory:

BoxLang Runtime ClassLoader
├── Core BIFs & Runtime Classes
├── Module A ClassLoader
│   └── libs/moduleA-dependency.jar
├── Module B ClassLoader
│   └── libs/moduleB-dependency.jar  (no conflict with Module A)
└── Application ClassLoader
    └── Application-specific JARs (this.javaSettings)

This prevents JAR version conflicts between modules — each module's libs/ directory is visible only to that module.

Key Java Packages

Package	Contents
ortus.boxlang.runtime	BoxRuntime, configuration
ortus.boxlang.runtime.bifs	BIF base classes, annotations
ortus.boxlang.runtime.context	Context classes, scope resolution
ortus.boxlang.runtime.scopes	Scope implementations, Key
ortus.boxlang.runtime.types	BoxArray, BoxStruct, IStruct, etc.
ortus.boxlang.runtime.events	BaseInterceptor, InterceptorService
ortus.boxlang.runtime.services	All service classes
ortus.boxlang.runtime.modules	ModuleRecord, ModuleService
ortus.boxlang.runtime.dynamic	DynamicObject, Java interop
ortus.boxlang.runtime.loader	Class loading, bytecode generation
ortus.boxlang.compiler.ast	AST node classes

Virtual Threads and Project Loom

BoxLang uses JRE 21 virtual threads (Project Loom) for its default executor:

// Virtual thread executor (default in BoxLang)
// - Lightweight: millions can coexist
// - Ideal for I/O-bound work (HTTP, DB, file I/O)
// - Automatically unmounted during blocking operations

ExecutorService virtualExec = Executors.newVirtualThreadPerTaskExecutor();

// BoxLang's AsyncService uses virtual threads by default:
// Type.VIRTUAL → Executors.newVirtualThreadPerTaskExecutor()
// Type.FIXED   → Executors.newFixedThreadPool(n)
// Type.CACHED  → Executors.newCachedThreadPool()

Java CDS (Class Data Sharing)

BoxLang supports Java CDS archives for faster startup:

# Generate a CDS archive
java -Xshare:dump -XX:SharedArchiveFile=boxlang.jsa -jar boxlang.jar

# Use the archive on startup (significantly faster cold starts)
java -Xshare:on -XX:SharedArchiveFile=boxlang.jsa -jar boxlang.jar

Runtime Configuration Access

// Get boxlang.json configuration
BoxLangConfiguration config = runtime.getConfiguration();

boolean debugMode   = config.debugMode;
String  timezone    = config.timezone;
IStruct modules     = config.modules;
IStruct caches      = config.caches;
IStruct datasources = config.datasources;

// Get a module's settings
IStruct moduleSettings = config.modules
    .getAsStruct( Key.of("bx-redis") )
    .getAsStruct( Key.of("settings") );

Embedding BoxLang in a Java Application

import ortus.boxlang.runtime.BoxRuntime;
import ortus.boxlang.runtime.context.ScriptingRequestBoxContext;
import ortus.boxlang.runtime.scopes.Key;

// Start the runtime
BoxRuntime runtime = BoxRuntime.getInstance( true );

// Create a scripting context
ScriptingRequestBoxContext context = new ScriptingRequestBoxContext( runtime.getRuntimeContext() );

// Set variables
context.getScope( VariablesScope.name ).put( Key.of("greeting"), "Hello!" );

// Execute BoxLang code
runtime.executeStatement( "println( greeting )", context );

// Execute a file
runtime.executeTemplate( "/path/to/script.bxs", context );

// Shutdown
runtime.shutdown();

Attempt — Null-Safe Value Wrapper

Attempt<T> is a fluent, immutable wrapper for values that may be null or invalid. It is analogous to Java's Optional but with built-in BoxLang validation support. Used extensively in BIFs and services, especially for optional argument handling.

import ortus.boxlang.runtime.dynamic.Attempt;

// Create an attempt from any value (including null)
Attempt<String> attempt = Attempt.of( arguments.get( Key.of("name") ) );
Attempt<Integer> empty  = Attempt.empty();

// Basic presence checks
if ( attempt.isPresent() ) { ... }
if ( attempt.isEmpty() )   { ... }

// Get value (throws NoElementException if empty)
String value = attempt.get();

// Get with default
String value = attempt.orElse( "default" );
String value = attempt.orElseGet( () -> computeDefault() );

// Throw a specific exception if empty
Attempt.of( null ).orThrow( "mymodule.NotFound", "Value not found" );

// Map and filter
Attempt<Integer> len = attempt.map( s -> s.length() );
Attempt<String> filtered = attempt.filter( s -> s.length() > 3 );

// Build a stream
attempt.stream().forEach( v -> process(v) );

Attempt with Validation

// Validate type (uses BoxLang's isValid() function)
Attempt.of( value ).toBeType( "email" ).isValid();  // true/false

// Range validation (inclusive)
Attempt.of( 42 ).toBeBetween( 1.0, 100.0 ).isValid();

// Regex pattern
Attempt.of( "hello" ).toMatchRegex( "^[a-z]+$" ).isValid();
Attempt.of( "HELLO" ).toMatchRegex( "^[a-z]+$", false ).isValid(); // case-insensitive

// Custom predicate
Attempt.of( user ).toSatisfy( u -> u.isActive() ).isValid();

Using Attempt in BIF Argument Handling

@Override
public Object invoke( IBoxContext context, ArgumentsScope arguments ) {
    // getAsAttempt returns Attempt<T> — safe for optional params
    String name    = arguments.getAsAttempt( Key.of("name"), String.class ).orElse( "World" );
    Integer timeout = arguments.getAsAttempt( Key.of("timeout"), Integer.class ).orElse( 30 );

    return "Hello, " + name + "!";
}

Type Casters

BoxLang provides a rich set of type casters in ortus.boxlang.runtime.dynamic.casters. Each returns a CastAttempt<T> (similar to Attempt) with .wasSuccessful() and .get().

import ortus.boxlang.runtime.dynamic.casters.*;

// Safe casting — returns CastAttempt
CastAttempt<String>  strAttempt  = StringCaster.attempt( value );
CastAttempt<Integer> intAttempt  = IntegerCaster.attempt( value );
CastAttempt<Long>    longAttempt = LongCaster.attempt( value );
CastAttempt<Double>  dblAttempt  = DoubleCaster.attempt( value );
CastAttempt<Boolean> boolAttempt = BooleanCaster.attempt( value );

if ( intAttempt.wasSuccessful() ) {
    int n = intAttempt.get();
}

// Direct casting (throws if fails)
String  str  = StringCaster.cast( value );
Integer num  = IntegerCaster.cast( value );
Boolean bool = BooleanCaster.cast( value );
Array   arr  = ArrayCaster.cast( value );
IStruct strc = StructCaster.cast( value );

// Specific casters available:
// ArrayCaster, BooleanCaster, DateTimeCaster, DoubleCaster,
// FloatCaster, IntegerCaster, KeyCaster, LongCaster,
// NumberCaster, QueryCaster, StringCaster, StructCaster,
// UUIDCaster, XMLCaster, ThrowableCaster, FunctionCaster

IService — Creating Custom Runtime Services

Implement IService to create a service that's lifecycle-managed by the BoxLang runtime. The runtime discovers and calls lifecycle methods automatically.

import ortus.boxlang.runtime.services.IService;
import ortus.boxlang.runtime.scopes.Key;

public class MyCustomService implements IService {

    private static final Key SERVICE_NAME = Key.of( "MyCustomService" );
    private BoxLangLogger     logger;

    @Override
    public Key getName() {
        return SERVICE_NAME;
    }

    @Override
    public void onConfigurationLoad() {
        // Called when boxlang.json is loaded; access config here
        this.logger = BoxRuntime.getInstance().getLoggingService().getLogger( "mycustomservice" );
        logger.debug( "Configuration loaded" );
    }

    @Override
    public void onStartup() {
        logger.info( "MyCustomService started" );
        // Initialize resources, open connections, warm up caches, etc.
    }

    @Override
    public void onShutdown( Boolean force ) {
        logger.info( "MyCustomService shutting down (force={})", force );
        // Release resources, close connections, flush buffers
    }

    // Add your service-specific methods:
    public String doSomething( String input ) {
        return input.toUpperCase();
    }
}

Registering a Service in a Module

// ModuleConfig.bx (via Java in onLoad)
// or register directly from Java:
BoxRuntime.getInstance().registerService( new MyCustomService() );

// ModuleConfig.bx
class {
    function onLoad() {
        var svc = createObject( "java", "com.example.services.MyCustomService" ).init()
        boxRuntime.registerService( svc )
        log.info( "MyCustomService registered" )
    }
}

Accessing a Registered Service

// Retrieve by name
MyCustomService svc = (MyCustomService) BoxRuntime.getInstance()
    .getService( Key.of("MyCustomService") );

svc.doSomething( "hello" );

References

• BoxLang Source
• BoxRuntime.java
• IBoxContext
• Attempt.java
• IService.java
• BoxLang Overview
• JEP 444 — Virtual Threads