RML Compilation

The rml parameter allows you to provide an RML (RDF Mapping Language) mapping file instead of a Velocity template. At runtime, the RML mapping is compiled into an equivalent MTL (Mapping Template Language) template and then executed normally.

This is a feature of the Mapping Template component — it does not require the separate camel-chimera-rmlmapper module.

How It Works

1. The RML mapping file is read from the rml ChimeraResource.
2. The mapping is compiled to an MTL .vm template file, written to the basePath directory.
3. The compiled template is executed against the readers in the exchange body.

Constraints

• rml and template are mutually exclusive — you cannot set both.
• Typically used with the mapt://readers input format, since RML mappings often reference multiple logical sources.

Parameters

All Mapping Template parameters apply. The key parameter is:

Parameter	Type	Required	Default	Description
rml	ChimeraResourceBean	Yes	—	Resource pointing to an RML mapping file (typically Turtle). See ChimeraResource.

Example

Compile and execute an RML mapping against two CSV readers:

Java DSLYAML

ChimeraResourceBean rmlMapping = new ChimeraResourceBean(
    "file://./data/mapping.ttl", "rml");
getCamelContext().getRegistry().bind("rmlMapping", rmlMapping);

from("direct:reader1")
    .setVariable("readerFormat", constant("csv"))
    .setVariable("readerName", constant("reader1"))
    .to("direct:aggregate");

from("direct:reader2")
    .setVariable("readerFormat", constant("csv"))
    .setVariable("readerName", constant("reader2"))
    .to("direct:aggregate");

from("direct:aggregate")
    .aggregate(constant(true), new ReadersAggregation())
    .completionSize(2)
    .to("mapt://readers?rml=#bean:rmlMapping&basePath=./output");

- beans:
    - name: rmlMapping
      type: com.cefriel.util.ChimeraResourceBean
      properties:
        url: "file://./data/mapping.ttl"
        serializationFormat: "rml"

- route:
    id: reader1
    from: "direct:reader1"
    steps:
      - setVariable:
          name: readerFormat
          constant: "csv"
      - setVariable:
          name: readerName
          constant: "reader1"
      - to: "direct:aggregate"

- route:
    id: reader2
    from: "direct:reader2"
    steps:
      - setVariable:
          name: readerFormat
          constant: "csv"
      - setVariable:
          name: readerName
          constant: "reader2"
      - to: "direct:aggregate"

- route:
    id: aggregate
    from: "direct:aggregate"
    steps:
      - aggregate:
          constant: true
          aggregationStrategy: "#class:com.cefriel.aggregationStrategy.ReadersAggregation"
          completionSize: 2
          steps:
            - to:
                uri: "mapt://readers"
                parameters:
                  rml: "#rmlMapping"
                  basePath: "./output"

The compiled MTL template is written to the basePath directory (e.g., ./output/template.rml.vm).