Error executing “Hello World” for AWS Lambda in Java

Question

I have written following Hello World Lambda which I am executing by uploading on AWS via AWS toolkit for Eclipse.

public class HelloWorldLambdaHandler implements RequestHandler<String, String> {

    public String handleRequest(String input, Context context) {

        System.out.println("Hello World! executed with input: " + input);

        return input;

    }

}

I am getting the following error when executing the above code. Any idea what I may be doing wrong here? BTW Maven project which has this handler doesn't have any other class and the only dependency is aws-lambda-java-core version 1.1.0.

Skip uploading function code since no local change is found...

Invoking function...

==================== FUNCTION OUTPUT ====================

{"errorMessage":"An error occurred during JSON parsing","errorType":"java.lang.RuntimeException","stackTrace":[],"cause":{"errorMessage":"com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_OBJECT token\n at [Source: lambdainternal.util.NativeMemoryAsInputStream@2f7c7260; line: 1, column: 1]","errorType":"java.io.UncheckedIOException","stackTrace":[],"cause":{"errorMessage":"Can not deserialize instance of java.lang.String out of START_OBJECT token\n at [Source: lambdainternal.util.NativeMemoryAsInputStream@2f7c7260; line: 1, column: 1]","errorType":"com.fasterxml.jackson.databind.JsonMappingException","stackTrace":["com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:148)","com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:835)","com.fasterxml.jackson.databind.deser.std.StringDeserializer.deserialize(StringDeserializer.java:59)","com.fasterxml.jackson.databind.deser.std.StringDeserializer.deserialize(StringDeserializer.java:12)","com.fasterxml.jackson.databind.ObjectReader._bindAndClose(ObjectReader.java:1441)","com.fasterxml.jackson.databind.ObjectReader.readValue(ObjectReader.java:1047)"]}}}

 

Answer 1

Amazon cannot deserialize JSON to string. It is not compatible. So, for handling JSON you can use Map or a custom POJO. 

public class HelloWorldLambdaHandler {

    public String handleRequest(Map<String,Object> input, Context context) {

        System.out.println(input);

        return "Hello";

    }

}