CODEWITHSUNDEEP
javajsonamazon-dynamodb
Prateek
Prateek

Reputation: 373

How to perform an updateItem operation with a JSON payload on a Dynamo DB table

The Dynamo DB document API allows put operation using a json payload

Item item = Item.fromJSON(payload);
table.putItem(item);

However I couldn't find a similar way for performing an updateItem with a Json payload.

Is there a Dynamo DB support for that?

Upvotes: 4

Views: 3011

Answers (3)

abhisekpaul
abhisekpaul

Reputation: 515

Here is a snippet as to how you would do it in Javascript. 

let updateExpression = 'SET ';
let expressionAttributeValues = {};

const keys = Object.keys(payload);
for (const key of keys) {
  updateExpression += `${key}=:${key},`;
  expressionAttributeValues[`:${key}`] = payload[key];
}
updateExpression=updateExpression.slice(0,-1);

let params = {  
  TableName : 'your_table_name',
  Key: {
    id: id
  }, 
  UpdateExpression : updateExpression,
  ExpressionAttributeValues : expressionAttributeValues,
  ReturnValues: "ALL_NEW"
}

db.update(params,(err, result)=>{});

Upvotes: 5

Baron Von Derlan
Baron Von Derlan

Reputation: 56

I was struggling with this for a while in the end you have to use a map.

UpdateItemOutcome updateItemOutcome = table.updateItem(
                new UpdateItemSpec()
                        .withPrimaryKey("id", "yourId")                            
                        .withUpdateExpression("SET document.field = :field")
                        .withValueMap(new ValueMap()
                                        .withMap(":field", "map of key value pairs that will get serialized to json")));

Upvotes: 1

Daniela Miao
Daniela Miao

Reputation: 1373

The UpdateItemSpec currently doesn't accept Item as input -- you will have to parse the json content first (presumably via Item.fromJSON) and then use either AttributeUpdate or UpdateExpression to specify the update action on each individual field (SET, ADD etc.)

Here is the documentation to using UpdateExpression to update an item http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/JavaDocumentAPIItemCRUD.html#JavaDocumentAPIItemUpdate

Upvotes: 0

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