[DynamoDB] Expected params.Item['age'].N to be a string

I am trying to use node.js to insert an record to dynamoDB in lambda, but get this error,

Part of the source :

exports.handler = (event, content, callback) => {
    var params = {
      Item: {
       "UserId": {
            S: "u_"+Math.random()
        },
       "Age": {
            N: event.age
        }
      },
      TableName: "userdata"
     };
     dynamodb.putItem(params, function(err, data) {
       if (err) {
           console.log(err, err.stack); // an error occurred
           callback(null, data);
       }else{
           console.log(data);           // successful response
           callback(null, data);
       }
     });
};

Json data in my request body:

{
    "age":12
}

Solution 1:

DynamoDB expect the N value is a string, but not in number format, so you need to convert the value in number format before you call putItem method. The first

exports.handler = (event, content, callback) => {
    var params = {
      Item: {
       "UserId": {
            S: "u_"+Math.random()
        },
       "Age": {
            N: event.age.toString()
        }
      },
      TableName: "userdata"
     };
     dynamodb.putItem(params, function(err, data) {
       if (err) {
           console.log(err, err.stack); // an error occurred
           callback(null, data);
       }else{
           console.log(data);           // successful response
           callback(null, data);
       }
     });
};

Solution 2:

If you have use apiGateway, you can change the data at body mapping template in "Integration Request", by adding double quotation marks, an example:

#set($inputRoot = $input.path('$'))
{
  "age"    : "$inputRoot.age"
}

Reference:

https://stackoverflow.com/questions/44011192/error-expected-params-itemid-n-to-be-a-string