CAMEL-23757: Add Java DSL model writer for full-circle DSL transformation

[davsclaus]

Summary

• Add a new core/camel-java-io module that generates fluent Java DSL source code from Camel model definitions
• Enables full-circle DSL transformation: XML/YAML → Model → Java DSL (and back via existing parsers)
• Follows the same code-generation pattern as existing camel-xml-io and camel-yaml-io modules

Architecture

Layer	XML	YAML	Java DSL (new)
Module	core/camel-xml-io	core/camel-yaml-io	core/camel-java-io
Generated class	ModelWriter	YamlModelWriter	JavaDslModelWriter
Support class	BaseWriter	YamlModelWriterSupport	JavaDslModelWriterSupport
Package	o.a.c.xml.out	o.a.c.yaml.out	o.a.c.java.out
Mojo	XmlModelWriterGeneratorMojo	YamlModelWriterGeneratorMojo	JavaDslModelWriterGeneratorMojo
Template	model-writer.vm	model-yaml-writer.vm	model-java-dsl-writer.vm

Example Output

from("direct:start")
    .routeId("myRoute")
    .choice()
        .when(simple("${header.type} == 'a'"))
            .to("mock:a")
        .when(simple("${header.type} == 'b'"))
            .to("mock:b")
        .otherwise()
            .to("mock:other")
    .end()
    .to("mock:result");

New Files

• JavaDslModelWriterGeneratorMojo.java — Mojo extending ModelWriterGeneratorMojo for code generation
• model-java-dsl-writer.vm — Velocity template producing the generated JavaDslModelWriter class
• core/camel-java-io/ — New module with JavaDslModelWriterSupport (DSL rendering helpers) and generated JavaDslModelWriter
• Test suite covering simple routes, choice/when/otherwise, filter, split, setHeader, setVariable, transform, wireTap, multicast, toD, removeHeader, multiple expression languages, and writer reusability

Test Plan

• Unit tests for all major EIP patterns (12 tests)
• Expected output files for exact string comparison
• Writer reusability test (same instance, multiple routes)
• Full root build passes (mvn clean install -DskipTests)

Claude Code on behalf of Claus Ibsen

🤖 Generated with Claude Code

[github-actions]

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[github-actions]

🧪 CI tested the following changed modules:

• catalog/camel-catalog
• core
• core/camel-api
• core/camel-core-model
• core/camel-java-io
• core/camel-xml-io
• tooling/maven/camel-package-maven-plugin
• tooling/spi-annotations

ℹ️ Dependent modules were not tested because the total number of affected modules exceeded the threshold (50). Use the test-dependents label to force testing all dependents.

⚠️ Some tests are disabled on GitHub Actions (@DisabledIfSystemProperty(named = "ci.env.name")) and require manual verification:

• core: 2 test(s) disabled on GitHub Actions

Build reactor — dependencies compiled but only changed modules were tested (8 modules)

• Camel :: API
• Camel :: Catalog :: Camel Catalog
• Camel :: Core Model
• Camel :: Core Modules
• Camel :: Java DSL IO
• Camel :: Maven Plugins :: Camel Maven Package
• Camel :: SPI Annotations
• Camel :: XML IO

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