NiFi 1.6：JoltTransformJSON用FlowFile属性作Jolt spec报错咨询

Unfortunately, Apache NiFi 1.6's JoltTransformJSON processor does NOT support using a FlowFile attribute as the Jolt specification—that's exactly why you're hitting the "JSON Spec provided is not valid JSON format" error.

Here's what's happening: When you try to reference a FlowFile attribute (like ${jolt.spec}) in the Jolt Specification field of the 1.6 processor, it doesn't recognize that as a pointer to an attribute. Instead, it treats the reference string itself as the raw JSON spec. Since ${jolt.spec} isn't valid JSON syntax, the processor throws that validation error immediately.

If you're stuck on NiFi 1.6 and need to use a dynamic spec stored in a FlowFile attribute, you have a couple of workarounds:

• Use ExecuteScript with custom code: Write a Groovy or Java script that pulls the Jolt spec from the FlowFile's attributes, applies the Jolt transform to the FlowFile content, and writes the transformed content back to a new FlowFile. This gives you full control over the logic, but requires some scripting knowledge.
• Dynamic spec file workflow: First use a PutFile processor to write the spec from the FlowFile attribute into a temporary file. Then configure JoltTransformJSON to reference this temporary file as its spec. After the transform completes, use a DeleteFile processor to clean up the temporary file to avoid clutter.

For what it's worth, the ability to load Jolt specs directly from FlowFile attributes was added in later NiFi versions (starting around 1.9.0, if I recall correctly). In those versions, the JoltTransformJSON processor includes a dedicated configuration option to choose between inline spec, file reference, or FlowFile attribute as the spec source.

内容的提问来源于stack exchange，提问作者raghu