topic Re: How to achieve schema (columns and types) using @DiscoverSchema annotation in Talend Studio

How to achieve schema (columns and types) using @DiscoverSchema annotation

Anonymous — Fri, 02 Jan 2026 14:45:42 GMT

Hi All,

I am not able to get schema columns names for my input component as per module name using @DiscoverSchema,Please help me with code. I have written code like below in service class .I need to write any thing in dataset class.

thanks,

venkat.

@DiscoverSchema("guessSchema")
public Schema guessSchema(@Option("dataset") final VtigercrmComponentsDataSet dataset ,final RecordBuilderFactory factory)
{

final Schema.Entry.Builder entryBuilder = factory.newEntryBuilder();
final Schema.Builder schemaBuilder = factory.newSchemaBuilder(org.talend.sdk.component.api.record.Schema.Type.RECORD);

Schema.Type type = Schema.Type.STRING;
//return (Schema) schemaBuilder.withEntry(entryBuilder.withName("name").withType(type).withNullable(false).build());

return factory.newSchemaBuilder(Schema.Type.RECORD)
.withEntry(factory.newEntryBuilder().withName("ResponseContent").withType(Schema.Type.LONG).build()).build();
}

Re: How to achieve schema (columns and types) using @DiscoverSchema annotation

Anonymous — Mon, 25 Mar 2019 05:56:07 GMT

Hi @Venkat_C ,

This guess schema will work only if your dataset is named "guessSchema", is it the case?

Re: How to achieve schema (columns and types) using @DiscoverSchema annotation

igorbeslic — Thu, 28 Mar 2019 14:43:31 GMT

Hi @Venkat_C did you get it working?

My team had same problem see thread:

https://community.talend.com/t5/Component-Development/Producer-and-DiscoverScheme/m-p/149874#M339

If you got it working what TS version you work with and which API version you use to develop your components?

Thank you!

Re: How to achieve schema (columns and types) using @DiscoverSchema annotation

Anonymous — Fri, 29 Mar 2019 06:00:43 GMT

Hi @igorbeslic ,

Yah,its working perfectly '@DiscoverSchema,i have declare List instance in my dataset class as like below and written @DiscoverSchema in service class.please find below link,it will use for create schema.

https://talend.github.io/component-runtime/main/1.1.3/record-types.html

@Option
@Structure(discoverSchema = "guessTableSchema",type=Type.IN)
@Documentation(value = "List of field names to return in the response.")
private List<String> fields = new ArrayList<>();

regards,

venkat

Re: How to achieve schema (columns and types) using @DiscoverSchema annotation

igorbeslic — Fri, 29 Mar 2019 20:10:57 GMT

Hi @Venkat_C thank you for your hints! Still for me documentation links are worthless. In link you provided there is no any note about:

@Option
@Structure(discoverSchema = "guessTableSchema",type=Type.IN)
@Documentation(value = "List of field names to return in the response.")
private List<String> fields = new ArrayList<>();

Do you have your component code available at GitHub? I sound desperate, but I think it would help more than all Telned documentation links people share in this forum. Or if you can share in this thread all important parts?

I used your hints with "@Structure" annotation but it does not trigger "@DiscoverSchema" method in "@Service" class. I put Talend Studio 7.2.1 M3 in debug mode and it does not track any interaction with service class. The "Discover schema" button in TS UI triggers "@Producer" method in my mapper's source class (invoked by "org.talend.sdk.component.runtime.di.schema.TaCoKitGuessSchema#guessSchemaThroughResult(java.lang.Object)").

Are you sure schema you get in your UI really comes from service annotated method "@DiscoverSchema"?

Thank you very much!

Re: How to achieve schema (columns and types) using @DiscoverSchema annotation

Anonymous — Fri, 29 Mar 2019 21:39:55 GMT

Hi Igor

Please dont mix two API - both use the same action.

1. @Structure is to have completion on a configuration field,
2. Guess Schema button is to initialize the struct associated to the component. For inputs, it tries to match a discover schema action based on the dataset used in the input configuration, if none is found it runs the producer method to get data.

I suspect something is fishy in the second case for you - was your action name originally if I recall correctly. Did you fix it, redeployed the component and restarted the studio or used the reload feature?

If still an issue please share your current/updated code to let us check what is missing.

Re: How to achieve schema (columns and types) using @DiscoverSchema annotation

igorbeslic — Mon, 01 Apr 2019 11:33:02 GMT

Hi @rmannibucau my component project is here

https://github.com/igorbeslic/talend-poc

Service implementation:

https://github.com/igorbeslic/talend-poc/blob/master/src/main/java/com/liferay/ebus/service/EBusService.java

Once deployed Talend Studio never invokes:

@DiscoverSchema(value = "Dataset")
public Schema discoverSchema(
	@Option("dataset") Dataset dataset,
	final RecordBuilderFactory recordBuilderFactory) {
//...
}

Thank you very much!!!

UPDATE:

I debug GuessSchema:

public TaCoKitGuessSchema(final PrintStream out, final Map<String, String> configuration, final String plugin,
            final String family, final String componentName, final String action)

last argument, "action" passed to TaCoKitGuessSchema is null. What could be reason for it?

Re: How to achieve schema (columns and types) using @DiscoverSchema annotation

Safus — Fri, 05 Feb 2021 11:58:54 GMT

Hi,

someone is facing this problem with the @DiscoverSchema ?

The method in my service class is triggered and my schema is created but the button never respects the order and never returning the same order.

It's all-time random :

Any Help ?

Thank you