CAMEL-21208: Replace manual string-based code generation with FreeMarker templates

[gnodet]

JIRA: CAMEL-21208

Summary

• Add FreeMarker 2.3.34 as a template engine dependency to camel-jbang-core
• Create TemplateHelper utility using FreeMarker's square bracket syntax ([=var], [#if]...[/#if]) to avoid conflicts with ${...} (Maven/Camel expressions) and <...> (XML tags) in generated content
• Convert all 23 .tmpl template files to .ftl FreeMarker templates with proper directives for conditionals and loops
• Refactor ExportCamelMain, ExportSpringBoot, ExportQuarkus, Export, Run, and Init commands to use TemplateHelper instead of manual StringBuilder/replaceAll/replaceFirst code generation
• Extract shared helpers (buildRepositoryList, buildDependencyList, formatBuildProperties, mavenGavComparator) into ExportBaseCommand to eliminate duplication
• Maintain backward compatibility for catalog-provided templates in ExportSpringBoot (legacy regex processing path)
• Remove 4 unreferenced templates (main-docker-*.tmpl, main-jkube-pom.tmpl)
• Keep deprecated bind templates (.tmpl) used by TemplateProvider

Motivation

The existing code generation approach used raw string manipulation (replaceFirst, replaceAll, StringBuilder.append) to produce POM files, Dockerfiles, README files, and source code. This was:

• Error-prone (regex escaping issues, ordering dependencies between replacements)
• Hard to read and maintain (XML structure buried in Java string concatenation)
• Difficult to extend (adding new conditional sections required careful regex surgery)

FreeMarker templates make the generated output structure visible and maintainable, with proper control flow ([#if], [#list]) replacing ad-hoc string manipulation.

Test plan

• All 311 camel-jbang-core tests pass
• All 128 camel-jbang-plugin-kubernetes tests pass
• CI build passes

[github-actions]

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[github-actions]

🧪 CI tested the following changed modules:

• dsl/camel-jbang/camel-jbang-core
• dsl/camel-jbang/camel-jbang-plugin-kubernetes

All tested modules (26 modules)

• Camel :: Coverage
• Camel :: Coverage [pom]
• Camel :: JBang :: Core
• Camel :: JBang :: Core [jar]
• Camel :: JBang :: Integration tests
• Camel :: JBang :: Integration tests [jar]
• Camel :: JBang :: MCP
• Camel :: JBang :: MCP [jar]
• Camel :: JBang :: Main
• Camel :: JBang :: Main [jar]
• Camel :: JBang :: Plugin :: Edit
• Camel :: JBang :: Plugin :: Edit [jar]
• Camel :: JBang :: Plugin :: Generate
• Camel :: JBang :: Plugin :: Generate [jar]
• Camel :: JBang :: Plugin :: Kubernetes
• Camel :: JBang :: Plugin :: Kubernetes [jar]
• Camel :: JBang :: Plugin :: Route Parser
• Camel :: JBang :: Plugin :: Route Parser [jar]
• Camel :: JBang :: Plugin :: Testing
• Camel :: JBang :: Plugin :: Testing [jar]
• Camel :: JBang :: Plugin :: Validate
• Camel :: JBang :: Plugin :: Validate [jar]
• Camel :: Launcher
• Camel :: Launcher [jar]
• Camel :: Launcher :: Container
• Camel :: Launcher :: Container [pom]

[Croway]

can this be extracted to avoid code duplication?

[gnodet]

Claude Code on behalf of Guillaume Nodet

Good catch. Looking at this more carefully — the Dockerfile template rendering now uses FreeMarker through the base class, and the Quarkus override handles the fast-jar vs uber-jar distinction which genuinely needs different logic. So the apparent duplication in Export.java line 311 is the shared base implementation. Will add a clarifying comment.

[apupier]

Hey AI agent, please rebase and resolve the conflict