camel-language-rhai

Rhai scripting language for rust-camel

Overview

camel-language-rhai provides a Rhai scripting language integration for rust-camel, similar to Apache Camel's Groovy or JavaScript language support. Rhai is an embedded scripting language for Rust with no external dependencies.

Available Variables

Scripts have access to these variables injected from the Exchange:

Variable	Type	Description
`body`	String	Message body as text
`headers`	Map	Message headers as a key-value map
`properties`	Map	Exchange properties as a key-value map

Read-only API (`create_expression` / `create_predicate`)

Function	Description
`header("name")`	Look up a header value by name
`set_header("key", value)`	Set a header visible within the same script evaluation (not propagated back)
`property("name")`	Look up an exchange property by name
`set_property("key", value)`	Set a property visible within the same script evaluation (not propagated back)

Note: set_header and set_property in read-only mode are local to the script evaluation. Changes are not propagated back to the Exchange.

Mutating API (`create_mutating_expression`)

Use create_mutating_expression when you need script changes to persist back to the Exchange. The mutating engine uses direct map assignment instead of helper functions:

headers["tenant"] = "acme";        // set header — propagated back
properties["trace"] = "enabled";   // set property — propagated back
body = "new content";              // set body — propagated back
let v = headers["existing"];       // read header

Changes are applied atomically: if the script throws an error, all modifications are rolled back and the Exchange is restored to its pre-execution state.

The .script() builder method uses this API automatically:

RouteBuilder::from("direct:input")
    .script("rhai", r#"headers["tenant"] = "acme"; body = body + "_processed""#)
    .to("log:result")
    .route_id("script-example")
    .build()?;

Usage

use camel_language_rhai::RhaiLanguage;
use camel_language_api::Language;

let lang = RhaiLanguage::new();

// Predicate using header lookup
let pred = lang.create_predicate(r#"header("type") == "order""#).unwrap();

// Expression with string concatenation
let expr = lang.create_expression(r#"body + " processed""#).unwrap();

// Full Rhai scripting
let expr = lang.create_expression(r#"
    if header("priority") == "high" {
        "URGENT: " + body
    } else {
        body
    }
"#).unwrap();

Registration

use camel_language_rhai::RhaiLanguage;

let mut ctx = CamelContext::new();
ctx.register_language("rhai", Box::new(RhaiLanguage::new())).unwrap();

License

Apache-2.0

camel-language-rhai 0.5.1