KSQL：UDF 不接受参数 (STRING, STRING)

Question

I'm running in to a problem with KSQL while trying to set up an ETL pipeline using a UDF. At some point in the ETL process I need to isolate specific info from a description field (VARCHAR) in my data. A made-up example for context:

description = "species=dog.sex=male.color=blonde.age=10." (the real data is formatted in the same way)

I've written a simple UDF to isolate any information on demand. It looks like this:

package com.my.package;

/** IMPORTS **/
import io.confluent.ksql.function.udf.Udf;
import io.confluent.ksql.function.udf.UdfDescription;

/** ClASS DEFINITION **/
@UdfDescription(name = "extract_from_description",
                author = "Me",
                version = "0.0.1",
                description = "Given a description and a request for information, isolates and returns the requested information. Pass requested tag as 'tag='".) 
public class Extract_From_Description {

    @Udf(description = "Given a description and a request for information, isolates and returns the requested information. Pass requested tag as 'tag='.)
    public String extract_from_description(final String description, final String request) {
        return description.split(request)[1].split("\\.")[0];
    }
}

I can upload and register the function just fine, it's listed and described properly when I run:

ksql> list functions;
ksql> describe function EXTRACT_FROM_DESCRIPTION;

I call the function like this to create a new stream:

CREATE STREAM result AS
    SELECT recordId,
           OtherVariables,
           EXTRACT_FROM_DESCRIPTION(description, 'species=') AS species
    FROM parent_stream
    EMIT CHANGES;

There I get an error I can't make sense of:

Function 'extract_from_description' does not accept parameters (STRING, STRING). Valid alternatives are:

Apparently KSQL can't properly interpret what the input for the function is supposed to be (looks like it expects no input?) and I can't figure out why. I've read through documentation to see if I define my function in a weird way but can't find any differences between the examples and my function. I did notice there are supposed to be several ways to define the input a function takes and tried them all, but the result is always the same.

I use Maven to create the jar file for this function (JDK1.8.0_201). Can anyone help me figure out what's going on?

TL;DR: My KSQL UDF doesn't accept input of type (String, String) even though the function specifies the input should be of type (String, String)

Answer 1

Found the problem, answering here for anyone that might run in to the same problem. You need to specify the parameters using @UdfParameter, like this:

import io.confluent.ksql.function.udf.UdfParameter; // add this to the list of imports

// add @UdfParameter(name) to each input variable
public String extract_from_description(@UdfParameter(value = "description") final String description, @UdfParameter(value = "request") final String request){
           
  function body

}