Interceptors

Create module interceptors to listen and react to BoxLang runtime events

Interceptors follow the Observer/Intercepting Filter pattern, letting your module react to runtime events. Create them in pure BoxLang or Java.

🟦 BoxLang Interceptors

Register interceptors in your ModuleConfig.bx configure() method:

ModuleConfig.bx:

function configure() {
    settings = {};

    // Register interceptors
    interceptors = [
        {
            class: "interceptors.RequestLogger",
            properties: {
                logHeaders: true,
                logBody: false
            }
        }
    ];

    // Declare custom interception points
    customInterceptionPoints = [
        "onBeforeGreeting",
        "onAfterGreeting"
    ];
}

File: interceptors/RequestLogger.bx

class {
    property name="logHeaders";
    property name="logBody";

    function onRequestStart( event ) {
        log.info( "Request started!" )

        if ( logHeaders ) {
            log.debug( "Headers: #event.getData()#" )
        }
    }

    function onRequestEnd( event ) {
        log.info( "Request ended!" )
    }
}

☕ Java Interceptors

Lambda Interceptors

Register inline closures as interceptors for quick event handling:

function configure() {
    interceptors = [
        {
            class: ( event ) => {
                log.info( "Quick listener fired!" )
            },
            name: "QuickListener@myModule"
        }
    ];
}

Custom Interception Points

Declare your own events that other code can listen to:

function configure() {
    customInterceptionPoints = [
        "onBeforeGreeting",
        "onAfterGreeting"
    ];
}

// Announce from module code
function doGreeting( required string name ) {
    announce( "onBeforeGreeting", { name: name } )

    var greeting = "Hello, #name#!"

    announce( "onAfterGreeting", { name: name, greeting: greeting } )

    return greeting
}

Listening to Lifecycle Events

Your ModuleConfig.bx is automatically registered as an interceptor, so you can add any event method directly:

class {
    // Listen for other modules loading
    function postModuleLoad( event ) {
        var moduleName = event.getData().moduleName
        log.info( "Module loaded: #moduleName#" )
    }

    // Listen for runtime startup
    function onModuleServiceStartup( event ) {
        log.info( "All modules are ready!" )
    }
}

Interceptor names follow the convention ClassName@moduleName. If not specified, it's auto-derived from the class name.

Next Steps

• Services — Global runtime services (Java only)
• Schedulers — Scheduled task management (Java only)
• Advanced Collaboration — System settings and class resolvers