Hello World

package helloworld;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import java.util.StringJoiner;

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;

/**
 * Handler for requests to Lambda function.
 */
public class App implements RequestHandler<Object, Object> {

    public Object handleRequest(final Object input, final Context context) {
        Map<String, String> headers = new HashMap<>();
        headers.put("Content-Type", "application/json");
        headers.put("X-Custom-Header", "application/json");
        try {
            final String pageContents = this.getPageContents("https://checkip.amazonaws.com");
            String output = String.format("{ \"message\": \"hello world\", \"location\": \"%s\" }", pageContents);
            return new GatewayResponse(output, headers, 200);
        } catch (IOException e) {
            return new GatewayResponse("{}", headers, 400);
        }
    }

    private String getPageContents(String address) throws IOException{
        BufferedReader br = null;
        StringJoiner lines = new StringJoiner(System.lineSeparator());
        try {
            URL url = new URL(address);
            br = new BufferedReader(new InputStreamReader(url.openStream()));
            String line;
            while ((line = br.readLine()) != null) {
                lines.add(line);
            }
        } finally {
            if (br != null) {
                br.close();
            }
        }
        return lines.toString();
    }
}

package helloworld;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * POJO containing response object for API Gateway.
 */
public class GatewayResponse {

    private final String body;
    private final Map<String, String> headers;
    private final int statusCode;

    public GatewayResponse(final String body, final Map<String, String> headers, final int statusCode) {
        this.statusCode = statusCode;
        this.body = body;
        this.headers = Collections.unmodifiableMap(new HashMap<>(headers));
    }

    public String getBody() {
        return body;
    }

    public Map<String, String> getHeaders() {
        return headers;
    }

    public int getStatusCode() {
        return statusCode;
    }
}

package helloworld;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;
import org.junit.Test;

public class AppTest {
  @Test
  public void successfulResponse() {
    App app = new App();
    GatewayResponse result = (GatewayResponse) app.handleRequest(null, null);
    assertEquals(result.getStatusCode(), 200);
    assertEquals(result.getHeaders().get("Content-Type"), "application/json");
    String content = result.getBody();
    assertNotNull(content);
    assertTrue(content.contains("\"message\""));
    assertTrue(content.contains("\"hello world\""));
    assertTrue(content.contains("\"location\""));
  }
}