Variable language

Q: How do I set a variable in YAML?

Use the setVariable step with name and an expression, for example setVariable: {name: question, simple: "${body}"}.

The variable language returns the value of one exchange variable (set with setVariable), or null when it is not set.

Name: variable · Crate: cameleer-core · Cargo feature: none, always included (build features) · Apache Camel: Variable

When to use it

Store intermediate results under a name (Camel 4 variables) without adding headers that would be sent to the next endpoint.
Keep the pieces of a multi-step agent flow apart: the user question, the retrieved context, the model answer.

Syntax

The expression text is the variable name. In Simple the same value is ${variable.name}, and ${variables} returns all of them. Variables are stored per exchange.

Examples

yaml example: variable-build-prompt

- route:
    id: variable-demo
    from:
      uri: direct:variable
      steps:
        - setVariable:
            name: question
            simple: "${body}"
        - setVariable:
            name: context
            constant: "Orders ship within 2 days."
        - setBody:
            simple: "Context: ${variable.context}\nQuestion: ${variable.question}"
        - setHeader:
            name: asked
            variable: question

text

When will my order ship?

text

Context: Orders ship within 2 days.
Question: When will my order ship?

json

{"body": "x", "variables": {"question": "When?", "score": 0.82}}

expression	result
`question`	`When?`
`score`	`0.82`
`missing`	(empty)

Options

The variable language has no options. It reads exchange variables only: Apache Camel's global: and route: prefixes are not interpreted by this language.

Rust DSL

rust

b.from("direct:variable-rust")
    .set_body(language("variable", "question"));

Common questions

How do I set a variable in YAML?

Use the setVariable step with name and an expression, for example setVariable: {name: question, simple: "${body}"}.

Are variables sent to endpoints?

No. Unlike headers, variables stay inside the exchange.

Simple language (${variable.name}, ${variables})
Header language, exchangeProperty language
Apache Camel Variable language

Found a problem?

If something on this page doesn't match what Cameleer does, or you hit a bug while building with it, please help fix it, whether you are a person or a coding agent: open an issue that describes what you saw, then fork the repository, fix it, add or update a test, run cargo test --workspace, and open a pull request. CONTRIBUTING.md explains the ground rules.