3 unstable releases

Uses new Rust 2024

new 0.3.5	Mar 8, 2026
0.3.0	Mar 8, 2026
0.2.1	Mar 4, 2026

#735 in Rust patterns

Used in 8 crates (via camel-core)

Apache-2.0

145KB
3K SLoC

camel-language-simple

Simple Language interpreter for rust-camel YAML DSL

Overview

camel-language-simple implements Apache Camel's Simple Language — a lightweight expression language for accessing exchange data and building predicates in route definitions.

Supported Expressions

Syntax	Description
`${header.name}`	Access a message header by name
`${body}`	Access the message body as text
`${body.field}`	Access JSON body field (dot-notation)
`${body.nested.field}`	Access nested JSON fields
`${body.array.0}`	Access array element by index
`${exchangeProperty.name}`	Access an exchange property

Note: Body field access (${body.field}) only works on Body::Json and returns Value::Null for other body types or missing fields.

Supported Operators

Operator	Example	Description
`==`	`${header.type} == 'order'`	Equality
`!=`	`${header.type} != null`	Inequality
`>`	`${header.age} > 18`	Greater than (numeric)
`<`	`${header.age} < 100`	Less than (numeric)
`>=`	`${header.count} >= 5`	Greater than or equal
`<=`	`${header.count} <= 10`	Less than or equal
`contains`	`${body} contains 'hello'`	String contains

Usage

use camel_language_simple::SimpleLanguage;
use camel_language_api::Language;

let lang = SimpleLanguage;

// Create a predicate
let pred = lang.create_predicate("${header.type} == 'order'").unwrap();

// Create an expression
let expr = lang.create_expression("${header.name}").unwrap();

Registration

SimpleLanguage is registered by default in CamelContext under the name "simple":

let ctx = CamelContext::new();
let lang = ctx.resolve_language("simple").unwrap();

License

Apache-2.0

Dependencies

~5.5–8MB
~133K SLoC