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Example Fn Java FDK : Service Connector Hub - Queue

This example provides a Function to use as a service connector hub target. The function accepts a typed event containing a batch of source messages.

Source

LoggingData.java

Dependencies

  • [fn-events] for ConnectorHubFunction classes.
  • [fn-events-testing] for ConnectorHubFunction testing library.

Demonstrated FDK features

This example showcases how to use the fn-event ConnectorHubFunction to use a Function as the target for Queue source.

Step by step

Set up the connector hub with Logging source and Function target:

The Function entrypoint extends the ConnectorHubFunction abstract class. Note: the func.yaml entrypoint remains the class which extends ConnectorHubFunction e.g. cmd: com.fnproject.fn.examples.Function::handler

Function.java

package com.fnproject.fn.examples;

import com.fnproject.events.ConnectorHubFunction;
import com.fnproject.events.input.ConnectorHubBatch;

public class Function extends ConnectorHubFunction<Employee> {

    public QueueService queueService;

    public Function() {
        this.queueService = new QueueService();
    }

    @Override
    public void handler(ConnectorHubBatch<Employee> batch) {
        for (Employee employee : batch.getBatch()) {
            queueService.readContent(employee);
        }
    }
}

The ConnectorHubBatch.java batch contains a list of messages from Queue as specified in Batch Settings.

The class Employee.java is a representation of messages received from the Queue.

Note the messages sent in to the Queue must be a valid String because Connector Hub forwards the message directly to the Function target.

  • wrong: a plain string
  • correct: "a plain string"

Function.java public class Function extends ConnectorHubFunction<Employee>.

To return an error response, throw RuntimeException.class. Doing so will cause the Function to return a 502 Retry policy

Test walkthrough

Unit testing ConnectorHubFunction is supported with the ConnectorHubTestFeature and FnTestingRule.

First of all, the class initializes the FnTestingRule harness, as explained in Testing Functions.

FunctionTest.java

package com.fnproject.fn.examples;

import static org.junit.Assert.assertEquals;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;
import java.util.Collections;
import com.fnproject.events.input.ConnectorHubBatch;
import com.fnproject.events.testing.ConnectorHubTestFeature;
import com.fnproject.fn.testing.FnResult;
import com.fnproject.fn.testing.FnTestingRule;
import org.junit.Rule;
import org.junit.Test;

public class FunctionTest {

    @Rule
    public FnTestingRule fn = FnTestingRule.createDefault();

    private final ConnectorHubTestFeature connectorHubTestFeature = ConnectorHubTestFeature.createDefault(fn);

    @Test
    public void testInvokeFunctionWithLoggingData() throws Exception {

        ConnectorHubBatch<Employee> event = createMinimalRequest();
        connectorHubTestFeature.givenEvent(event).enqueue();

        fn.thenRun(Function.class, "handler");

        FnResult result = fn.getOnlyResult();
        assertEquals(200, result.getStatus().getCode());
    }

    private static ConnectorHubBatch<Employee> createMinimalRequest() {
        Employee employee = new Employee();
        employee.setName("foo");

        ConnectorHubBatch<Employee> event = mock(ConnectorHubBatch.class);

        when(event.getBatch()).thenReturn(Collections.singletonList(employee));
        return event;
    }
}

Use connectorHubTestFeature.givenEvent(event).enqueue(); to queue the request event and invoke the Function with fn.thenRun(Function.class, "handler");.