README.md

Example Fn Java FDK : API Gateway

This example provides a Function to use as an API Gateway backend. The function accepts a typed request for easy object handling and returns http response.

Dependencies

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

Demonstrated FDK features

This example showcases how to use the fn-event APIGatewayFunction to use a Function as the backend.

Step by step

Set the API Gateway and Function backend Adding a Function in OCI Functions as an API Gateway Back End

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

Function.java

import com.fnproject.events.APIGatewayFunction;
import com.fnproject.events.input.APIGatewayRequestEvent;
import com.fnproject.events.output.APIGatewayResponseEvent;
import com.fnproject.fn.api.Headers;
import org.apache.http.HttpStatus;

public class Function extends APIGatewayFunction<RequestEmployee, ResponseEmployee> {

    @Override
    public APIGatewayResponseEvent<ResponseEmployee> handler(APIGatewayRequestEvent<RequestEmployee> requestEvent) {
        ResponseEmployee employee = new ResponseEmployee();
        Optional<String> id = requestEvent.getQueryParameters().get("id");
        id.ifPresent(s -> employee.setId(Integer.parseInt(s)));

        if (requestEvent.getBody() != null) {
            employee.setName(requestEvent.getBody().getName());
        }

        return new APIGatewayResponseEvent.Builder<ResponseEmployee>()
            .statusCode(HttpStatus.SC_CREATED)
            .headers(Headers.emptyHeaders()
                .addHeader("X-Custom-Header", "HeaderValue")
                .addHeader("X-Custom-Header-2", "HeaderValue2"))
            .body(employee)
            .build();
    }
}

The APIGatewayRequestEvent.class requestUrl is relative to the deployment path prefix see API Gateway using HTTP backend

The class RequestEmployee.java is the request body type and ResponseEmployee.java is the response body type. These are passed in position 1 and 2 of abstract class Function.java public class Function extends APIGatewayFunction<RequestEmployee, ResponseEmployee> {.

To return an error response, throw RuntimeException.class.

Test walkthrough

Unit testing APIGatewayFunction is supported with the APIGatewayTestFeature and FnTestingRule.

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

FunctionTest.java

import static org.junit.Assert.*;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;
import java.io.IOException;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import com.fnproject.events.input.APIGatewayRequestEvent;
import com.fnproject.events.output.APIGatewayResponseEvent;
import com.fnproject.events.testing.APIGatewayTestFeature;
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 APIGatewayTestFeature apiGatewayFeature = APIGatewayTestFeature.createDefault(fn);

    @Test
    public void testHttpAttributes() throws IOException {
        RequestEmployee requestEmployee = new RequestEmployee();
        requestEmployee.setName("John");

        APIGatewayRequestEvent<RequestEmployee> event = mock(APIGatewayRequestEvent.class);

        when(event.getBody()).thenReturn(requestEmployee);
        when(event.getMethod()).thenReturn("POST");
        when(event.getRequestUrl()).thenReturn("/v2?id=123");
        when(event.getQueryParameters()).thenReturn(new QueryParametersImpl(Collections.singletonMap("id", Collections.singletonList("123"))));
        when(event.getHeaders()).thenReturn(Collections.unmodifiableMap(new HashMap<String, List<String>>() {{
            put("myHeader", Collections.singletonList("headerValue"));
        }}));

        apiGatewayFeature.givenEvent(event)
            .enqueue();

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

        APIGatewayResponseEvent<ResponseEmployee> responseEvent = apiGatewayFeature.getResult(ResponseEmployee.class);

        ResponseEmployee responseEventBody = responseEvent.getBody();
        assertEquals(123, responseEventBody.getId());
        assertEquals("John", responseEventBody.getName());
        assertEquals(Integer.valueOf(201), responseEvent.getStatus());
        assertEquals("HeaderValue", responseEvent.getHeaders().get("X-Custom-Header").get(0));
        assertEquals("HeaderValue2", responseEvent.getHeaders().get("X-Custom-Header-2").get(0));
    }
}

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

And get the Function response using APIGatewayResponseEvent<ResponseEmployee> responseEvent = apiGatewayFeature.getResult(ResponseEmployee.class);