AWS Lambda response in Java for Cognito

问题

How can I write an "AWS Lambda response" in Java so that Cognito is happy?

Something like this is passed to the lambda function

{
"version": number,
"triggerSource": "string",
"region": AWSRegion,
"userPoolId": "string",
"callerContext": 
    {
        "awsSdkVersion": "string",
        "clientId": "string"
    },
"request":
    {
        "userAttributes": {
            "string": "string",
            ....
        }
    },
"response": {}
}

Now I need to make the response in Java.. and send back to Cognito. At the moment Cognito throws an "InvalidLambdaResponseException".

Java code below just returns the event..

public class LambdaFunctionHandler implements RequestHandler<CognitoEvent, CognitoEvent> 
{
    @Override
    public CognitoEvent handleRequest(CognitoEvent arg0, Context arg1) 
    {
        return arg0;
    }
}

回答1:

You just need a class like this:

import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.NoArgsConstructor;
import lombok.Setter;

import java.util.Map;

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@JsonSerialize
public class Example {
    private int version;
    private String triggerSource;
    private String region;
    private String userPoolId;
    private Map<String, String> callerContext;
    private Request request;
    private Response response;

    @Getter
    @Setter
    @JsonSerialize
    public static class Request {
        private Map<String, String> userAttributes;
        public Request(Map<String, String> userAttr) {
            userAttributes = userAttr;
        }
    }

    @Getter
    @Setter
    @JsonSerialize
    public static class Response { }

}

That after you serialize will look like this:

{
  "version" : 1,
  "triggerSource" : "trigger",
  "region" : "us-east-1",
  "userPoolId" : "user-pool-id",
  "callerContext" : {
    "some-key" : "some-value"
  },
  "request" : {
    "userAttributes" : {
      "name" : "Michael J Leonard"
    }
  },
  "response" : { }
}

And have this as an input to your lambda. It might require some changes but this is an example of a template for the PostAuthentication lambda

来源：https://stackoverflow.com/questions/46526687/aws-lambda-response-in-java-for-cognito