'Error executing "Hello World" for AWS Lambda in Java

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 following error when executing above code. Any idea what I maybe doing wrong here? BTW Maven project which have this handler, doesn't have any other class and 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)"]}}}

aws-lambda

Solution 1:^[1]

For some reason Amazon can't deserialize json to a String. You would think String would be as general as input parameter as you can get but rightly or wrongly it's not compatible.

To handle JSON you can either use a Map or a custom POJO.

public class HelloWorldLambdaHandler {
    public String handleRequest(Map<String,Object> input, Context context) {
        System.out.println(input);
        return "Hello";
    }
}

Solution 2:^[2]

Read the error from the stack trace. It says "Can not deserialize instance of java.lang.String out of START_OBJECT token". The "START_OBJECT" token is '{'.

The problem was simply that you need to pass an actual String as input, e.g., "A String". This is your json input. Not {}. {} is not a String. You don't need any braces, just a string (in quotes). On the other hand, {} is a valid Person object, so it worked once you changed it to handle a Person as the input.

Solution 3:^[3]

I tried with the following value in the test :

"TestInput"

instead of :

{ Input : "TestInput"}

and it seems to have worked fine.

Solution 4:^[4]

The complete working solution is

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;
    }
}

then input has to be in double quotes as a String - "Test Input"

Solution 5:^[5]

The input window for the test configurator takes raw json, or strings.

If you pass raw json, AWS converts the json into a Map where the variable names are keys that map the respective values.
If you wrap the json in double quotes and delimit inner quotes, this is an acceptable Java string representation of a json object and can be parsed as usual.

Solution 6:^[6]

Workaround 1:

Instead of

{
  "key1": "value1",
  "key2": "value2",
  "key3": "value3"
}

use some String as input, as shown below

"anyString"

It'll work fine.

Workaround 2: please refer the answer of @Lionel Port.

Reason:

As @Lionel Port suggested, you must be having String as inputType in your handleRequest() method!

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

you can see here, input type is String and you're passing Json, that's why giving this error!

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	Lionel Port
Solution 2	Kelly Denehy
Solution 3	Samuel Hulla
Solution 4	kanaparthikiran
Solution 5	Javageek
Solution 6	Demobilizer

'Error executing "Hello World" for AWS Lambda in Java

Solution 1:[1]

Solution 2:[2]

Solution 3:[3]

Solution 4:[4]

Solution 5:[5]

Solution 6:[6]