Cannot pass string to AWS Lambda using InvokeRequest.withPayload() method

Question

I have a lambda function that accepts a String as an input parameter. When running the lambda function I get the following error: Can not deserialize instance of java.lang.String out of START_OBJECT token\n

This is what my code too call it looks like:

InvokeRequest request = new InvokeRequest();
final String payload = "";
request.withFunctionName(FUNCTION_NAME).withPayload((String) null);
InvokeResult invokeResult = lambdaClient.invoke(request);
Assert.assertEquals(new String (invokeResult.getPayload().array(), "UTF-8"), "Success");

And this is what my handler looks like:

public String handleRequest(String s, Context context) {}

Now the contents of the string don't matter, it could be null it could be anything. I don't use the input. The obvious solution is to remove it, but because of an annotation generator i'm using I can't do that. I've tried a ByteBuffer input, String, empty String, JSON String {\"s\":\"s\"} but nothing seems to work. I believe I need to pass in a string (i.e no {}). But since I'm using InvokeRequest I don't believe I can do that. Any suggestions would be greatly appreciated.

Try using the solution as provided here. Hope it'll help stackoverflow.com/questions/41616806/… — Showmik Bose
– Showmik Bose, Commented Aug 20, 2019 at 11:45
Thanks for the link! I actually followed that same tutorial and it didn't work. I appreciate it though! — AwesomeBrownGuy
– AwesomeBrownGuy, Commented Aug 20, 2019 at 14:18

Jan · Accepted Answer · 2020-06-26 08:59:57Z

0

It works by passing a JSON valid String.

String payload = "{ \"subject\" : \"content\"}";
request.withFunctionName(functionName)           
                .withPayload(payload);

At the receiving end you have to map it from Object to String again if that's what you want. Here I used Jackson ObjectMapper for this.

ObjectMapper objectMapper = new ObjectMapper();
        try {
            String payload = objectMapper.writeValueAsString(input);
        } catch (JsonProcessingException e) {
            e.printStackTrace();
        }

answered Jun 26, 2020 at 8:59

Jan

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