Using the YcFunction interface for a Java handler

Written by

Updated at September 23, 2024

To create a Java handler, you can implement the YcFunction interface. To do this, add the SDK to the dependencies.

Example of a valid handler:

import yandex.cloud.sdk.functions.YcFunction;
import yandex.cloud.sdk.functions.Context;

public class Handler implements YcFunction<Integer, String> {
  @Override
  public String handle(Integer i, Context c) {
    return String.valueOf(i);
  }
}

Warning

Specify two values for YcFunction type parameters: the first one represents the input argument type, the second one, the return value type. For the handle method, make sure to provide the invocation context as its second argument.

Examples of invalid handlers:

import yandex.cloud.sdk.functions.YcFunction;
import yandex.cloud.sdk.functions.Context;
// YcFunction has only one parameter type specified
// Handler should not have any type parameters (see the handler requirements)
public class Handler<T> implements YcFunction<T, Integer> {
  @Override
  public Integer handle(T i, Context c) {
    return 2;
  }
}

import yandex.cloud.sdk.functions.YcFunction;
import yandex.cloud.sdk.functions.Context;
// YcFunction has neither parameter types specified
public class Handler implements YcFunction {
  @Override
  public Object apply(Object i, Context c) {
    return i;
  }
}

You can use any classes as input and return types.

Note

Fields of these classes may have any access modifiers. For non-public fields, you do not have to write getter/setter.

Example of function information output

The following function receives a number as an input, outputs the function data obtained from the invocation context to the execution log, and returns data on whether the received number is even.

Warning

To invoke the function, use the Yandex Cloud CLI or an HTTP request with the ?integration=raw parameter.

Handler.java file:

import yandex.cloud.sdk.functions.YcFunction;
import yandex.cloud.sdk.functions.Context;

public class Handler implements YcFunction<Integer, Boolean> {

  private String format(String f, String s) {
    return String.format(f, s);
  }

  @Override
  public Boolean handle(Integer number, Context c) {
    System.out.println(format("Function name: %s", c.getFunctionName()));
    System.out.println(format("Function version: %s", c.getFunctionVersion()));
    // if no service account is selected, an empty line is printed
    System.out.println(format("Service account token: %s", c.getTokenJson()));
    return number % 2 == 0;
  }
}

Example of input data:

The log will contain the following:

Function name: <function_name>
Function version: <function_version_ID>
Service account token: <service_account_token>

Returned string:

false

Using the YcFunction interface for a Java handler

Example of function information outputExample of function information output

Was the article helpful?

Example of function information output