Converting DynamoDB JSON to Standard JSON with Java

You can use ItemUtils class in aws sdk. Below is sample code using Kotlin:

import com.amazonaws.services.dynamodbv2.document.ItemUtilsimport com.amazonaws.services.dynamodbv2.model.AttributeValuefun main(args: Array<String>) {    val data = HashMap<String,AttributeValue>()    data.put("hello",AttributeValue().withS("world"))    println(data.toString())    println(ItemUtils.toItem(data).toJSON())}

Output:

{hello={S: world,}}{"hello":"world"}

Below is the complete code for converting from Dynamo JSON to Standard JSON:

import com.amazonaws.services.dynamodbv2.document.Item;import com.amazonaws.services.dynamodbv2.document.internal.InternalUtils;import com.amazonaws.services.dynamodbv2.model.AttributeValue;import com.amazonaws.services.lambda.runtime.Context;import com.amazonaws.services.lambda.runtime.RequestHandler;import com.amazonaws.services.lambda.runtime.events.DynamodbEvent;import com.amazonaws.services.lambda.runtime.events.DynamodbEvent.DynamodbStreamRecord;import com.google.gson.Gson;import java.util.ArrayList;import java.util.List;import java.util.Map;/** * Main Lambda class to receive event stream, parse it to Survey * and process them. */public class SurveyEventProcessor implements        RequestHandler<DynamodbEvent, String> {    private static final String INSERT = "INSERT";    private static final String MODIFY = "MODIFY";    public String handleRequest(DynamodbEvent ddbEvent, Context context) {        List<Item> listOfItem = new ArrayList<>();        List<Map<String, AttributeValue>> listOfMaps = null;        for (DynamodbStreamRecord record : ddbEvent.getRecords()) {            if (INSERT.equals(record.getEventName()) || MODIFY.equals(record.getEventName())) {                listOfMaps = new ArrayList<Map<String, AttributeValue>>();                listOfMaps.add(record.getDynamodb().getNewImage());                listOfItem = InternalUtils.toItemList(listOfMaps);            }            System.out.println(listOfItem);            try {               // String json = new ObjectMapper().writeValueAsString(listOfItem.get(0));                Gson gson = new Gson();                Item item = listOfItem.get(0);                String json = gson.toJson(item.asMap());                System.out.println("JSON is ");                System.out.println(json);            }catch (Exception e){                e.printStackTrace();            }        }        return "Successfully processed " + ddbEvent.getRecords().size() + " records.";    }} 

Following is a simple solution which can be applied to convert any DynamoDB Json to Simple JSON.

//passing the reponse.getItems() public static Object getJson(List<Map<String,AttributeValue>> mapList) {    List<Object> finalJson= new ArrayList();    for(Map<String,AttributeValue> eachEntry : mapList) {        finalJson.add(mapToJson(eachEntry));    }    return finalJson;}//if the map is null then it add the key and value(string) in the finalKeyValueMappublic static Map<String,Object> mapToJson(Map<String,AttributeValue> keyValueMap){    Map<String,Object> finalKeyValueMap = new HashMap();    for(Map.Entry<String, AttributeValue> entry : keyValueMap.entrySet())     {        if(entry.getValue().getM() == null) {            finalKeyValueMap.put(entry.getKey(),entry.getValue().getS());        }        else {            finalKeyValueMap.put(entry.getKey(),mapToJson(entry.getValue().getM()));        }    }    return finalKeyValueMap;}

This will produce your desired Json in the form of List>. Then using the Gson you can convert it into the Json format.

Gson gson = new Gson();String jsonString = gson.toJson(getJson(response.getItems()));