Transform does not allow a type-only conversion

[gtg-bantonio]

Describe the bug

Good day, when we tried to use the Transform EIP, we can't remove the expression. According with the examples in Camel, it should be possible to only use type conversion only with this pattern.

- from:
    uri: direct:cheese
    steps:
      - transform:
          to-type: myDataType
      - to:
          uri: log:hello

Steps to reproduce the behavior

1. Add a new route
2. Add the Transform
3. Set only "To Type"
4. Try to run it
5. See error

Variant

Web Application

Container Management (if applicable)

Kubernetes

Operating System (if applicable)

Linux

Version

4.10.2

Relevant log output

org.apache.camel.FailedToCreateRouteException: Failed to create route: route-timer-test at: >>> Transform[Test] <<< in route: Route(route-timer-test)[From[timer:Test?repeatCount=1] -> [T... because: Both expression and data type set on transform EIP - please choose only one of them
	at org.apache.camel.reifier.RouteReifier.doCreateRoute(RouteReifier.java:246)
	at org.apache.camel.reifier.RouteReifier.createRoute(RouteReifier.java:88)
	at org.apache.camel.impl.DefaultModelReifierFactory.createRoute(DefaultModelReifierFactory.java:49)
	at org.apache.camel.impl.DefaultCamelContext.startRouteDefinitions(DefaultCamelContext.java:765)
	at org.apache.camel.impl.DefaultCamelContext.startRouteDefinitions(DefaultCamelContext.java:626)
	at org.apache.camel.impl.engine.AbstractCamelContext.doInit(AbstractCamelContext.java:2593)
	at org.apache.camel.support.service.BaseService.init(BaseService.java:85)
	at org.apache.camel.impl.engine.AbstractCamelContext.init(AbstractCamelContext.java:2211)
	at org.apache.camel.support.service.BaseService.start(BaseService.java:115)
	at org.apache.camel.impl.engine.AbstractCamelContext.start(AbstractCamelContext.java:2230)
	at org.apache.camel.impl.DefaultCamelContext.start(DefaultCamelContext.java:211)
	at org.apache.camel.main.KameletMain.doStart(KameletMain.java:405)
	at org.apache.camel.support.service.BaseService.start(BaseService.java:123)
	at org.apache.camel.dsl.jbang.core.commands.Run.runKameletMain(Run.java:1633)
	at org.apache.camel.dsl.jbang.core.commands.Run.run(Run.java:1002)
	at org.apache.camel.dsl.jbang.core.commands.Run.doCall(Run.java:369)
	at org.apache.camel.dsl.jbang.core.commands.CamelCommand.call(CamelCommand.java:71)
	at org.apache.camel.dsl.jbang.core.commands.CamelCommand.call(CamelCommand.java:37)
	at picocli.CommandLine.executeUserObject(CommandLine.java:2031)
	at picocli.CommandLine.access$1500(CommandLine.java:148)
	at picocli.CommandLine$RunLast.executeUserObjectOfLastSubcommandWithSameParent(CommandLine.java:2469)
	at picocli.CommandLine$RunLast.handle(CommandLine.java:2461)
	at picocli.CommandLine$RunLast.handle(CommandLine.java:2423)
	at picocli.CommandLine$AbstractParseResultHandler.execute(CommandLine.java:2277)
	at picocli.CommandLine$RunLast.execute(CommandLine.java:2425)
	at picocli.CommandLine.execute(CommandLine.java:2174)
	at org.apache.camel.dsl.jbang.core.commands.CamelJBangMain.run(CamelJBangMain.java:205)
	at org.apache.camel.dsl.jbang.core.commands.CamelJBangMain.run(CamelJBangMain.java:72)
	at main.CamelJBang.main(CamelJBang.java:36)
Caused by: java.lang.IllegalArgumentException: Both expression and data type set on transform EIP - please choose only one of them
	at org.apache.camel.reifier.TransformReifier.createProcessor(TransformReifier.java:36)
	at org.apache.camel.reifier.ProcessorReifier.makeProcessor(ProcessorReifier.java:843)
	at org.apache.camel.reifier.ProcessorReifier.addRoutes(ProcessorReifier.java:616)
	at org.apache.camel.reifier.RouteReifier.doCreateRoute(RouteReifier.java:238)

[davsclaus]

You can use marshal/unmarshal instead where you can refer to your data format

This transform EIP is hardly in use, and it has a mistake that its expression based but then the expression is mandatory in the model, but in the code it somehow ignores that. So the karavan tooling is correct but the eip in Camel has that problem.

[davsclaus]

https://issues.apache.org/jira/browse/CAMEL-22744

[gtg-bantonio]

@davsclaus that won't work because a data format is not the same as a data type. It took me a long to discover that, but I can't use a data type like google-sheets:application-x-struct to convert a JSON structure into a Google Sheets Data Range, and in Camel Main, it work as expected, just setting the toType.

[davsclaus]

Okay so this is to be fixed in Camel 4.17 onwards with a new transformDataType EIP you should use instead of transform.
And this will then be in any upcoming 4.18 LTS based Karavan release in the future.