Invoke lambda function handler java - aws-lambda

Question

I have a lambda function which has a handler which inturn has multiple routers. Each router corresponds to an API.
I have created a lambda client in java and need to call those APIs. To call these APIs, I need to invoke the handler and pass a payload to the client along with it. Can you guys help me with the syntax for invoking the handler and passing the payload.

Answer 1

If I understand your question correctly I first created a Lambda that looked like:
public class SampleHandler implements RequestStreamHandler {
private static final Logger logger = LogManager.getLogger(SampleHandler.class);
public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context) throws IOException {
logger.info("handlingRequest");
LambdaLogger lambdaLogger = context.getLogger();
ObjectMapper objectMapper = new ObjectMapper();
String inputString = new BufferedReader(new InputStreamReader(inputStream)).lines().collect(Collectors.joining("\n"));
JsonNode jsonNode = objectMapper.readTree(inputString);
String route = jsonNode.get("route").asText();
RouterResult routerResult = new RouterResult();
switch( route ) {
case "requestTypeA":
RequestTypeA requestTypeA = objectMapper.readValue(inputString, RequestTypeA.class);
routerResult.setResult(handleRequestTypeA(requestTypeA));
break;
case "requestTypeB":
RequestTypeB requestTypeB = objectMapper.readValue(inputString, RequestTypeB.class);
routerResult.setResult(handleRequestTypeB(requestTypeB));
break;
default:
logger.error( "don't know how to handle route of type \"" + route + "\n" );
routerResult.setResult("error");
}
outputStream.write(objectMapper.writeValueAsString(routerResult).getBytes(StandardCharsets.UTF_8));
logger.info("done with run, remaining time in ms is " + context.getRemainingTimeInMillis() );
}
private String handleRequestTypeA(RequestTypeA requestTypeA) {
logger.info("handling requestTypeA, requestTypeA.requestA is " + requestTypeA.getRequestA() );
return "handled requestTypeA";
}
private String handleRequestTypeB(RequestTypeB requestTypeB) {
logger.info("handling requestTypeB, requestTypeB.requestB is " + requestTypeB.getRequestB() );
return "handled requestTypeB";
}
}
with RouterRequest.java:
public class RouterRequest {
protected String route;
public String getRoute() {
return route;
}
}
and RequestTypeA.java:
public class RequestTypeA extends RouterRequest {
private String requestA;
public RequestTypeA() {
route = "requestTypeA";
}
public String getRequestA() {
return requestA;
}
public void setRequestA(String requestA) {
this.requestA = requestA;
}
}
and RequestTypeB.java
public class RequestTypeB extends RouterRequest {
private String requestB;
public RequestTypeB() {
route = "requestTypeB";
}
public String getRequestB() {
return requestB;
}
public void setRequestB(String requestB) {
this.requestB = requestB;
}
}
And a result class, RouterResult.java:
public class RouterResult {
private String result;
public String getResult() {
return result;
}
public void setResult(String result) {
this.result = result;
}
#Override
public String toString() {
return "RouterResult{" +
"result='" + result + '\'' +
'}';
}
}
Then, to invoke this Lambda, you will need a role that has the lambda:InvokeFunction permission. The code to invoke looks like:
public class RouterRunner {
private static final String AWS_ACCESS_KEY_ID = "<access key>";
private static final String AWS_SECRET_ACCESS_KEY = "<access secret>";
public static void main( String[] argv ) throws IOException {
AWSCredentials credentials = new BasicAWSCredentials( AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY );
AWSLambda lambda = AWSLambdaClientBuilder.standard()
.withRegion(Regions.US_WEST_2)
.withCredentials(new AWSStaticCredentialsProvider(credentials)).build();
RequestTypeA requestTypeA = new RequestTypeA();
requestTypeA.setRequestA("set from the runner, request type A");
ObjectMapper objectMapper = new ObjectMapper();
InvokeRequest invokeRequest = new InvokeRequest()
.withFunctionName("lambda-router")
.withPayload(objectMapper.writeValueAsString(requestTypeA));
invokeRequest.setInvocationType(InvocationType.RequestResponse);
InvokeResult invokeResult = lambda.invoke(invokeRequest);
String resultJSON = new String(invokeResult.getPayload().array(), StandardCharsets.UTF_8);
System.out.println( "result from lambda is " + resultJSON );
RouterResult routerResult = objectMapper.readValue(resultJSON, RouterResult.class);
System.out.println( "result.toString is " + routerResult.toString() );
RequestTypeB requestTypeB = new RequestTypeB();
requestTypeB.setRequestB("set from the runner, request type B");
invokeRequest = new InvokeRequest()
.withFunctionName("lambda-router")
.withPayload(objectMapper.writeValueAsString(requestTypeB));
invokeRequest.setInvocationType(InvocationType.RequestResponse);
invokeResult = lambda.invoke(invokeRequest);
resultJSON = new String(invokeResult.getPayload().array(), StandardCharsets.UTF_8);
System.out.println( "result from lambda is " + resultJSON );
routerResult = objectMapper.readValue(resultJSON, RouterResult.class);
System.out.println( "result.toString is " + routerResult.toString() );
}
}
There likely needs to be some error handling improvement and I'm sure you could make this a bit more efficient. But that's the overall idea. Ultimately on the Lambda side I convert the InputStream to a String and convert that String to some sort of object based on a common field in the request types. On the client side I convert the objects into JSON, send them out, and convert the result back from a JSON String back into the result object.