Using an Amazon S3 trigger to invoke a Lambda function
The Lambda function retrieves the source S3 bucket name and the key name of the uploaded object from the event parameter that it receives. The function uses the Amazon S3 getObject API to retrieve the content type of the object.
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Usage Example with Node:
Consuming an S3 event with Lambda using JavaScript.
const aws = require('aws-sdk');
const s3 = new aws.S3({ apiVersion: '2006-03-01' });
exports.handler = async (event, context) => {
// Get the object from the event and show its content type
const bucket = event.Records[0].s3.bucket.name;
const key = decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, ' '));
const params = {
Bucket: bucket,
Key: key,
};
try {
const { ContentType } = await s3.headObject(params).promise();
console.log('CONTENT TYPE:', ContentType);
return ContentType;
} catch (err) {
console.log(err);
const message = `Error getting object ${key} from bucket ${bucket}. Make sure they exist and your bucket is in the same region as this function.`;
console.log(message);
throw new Error(message);
}
};
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