Query S3 json file in AWS - node.js

Question

I have json file uploaded to s3
then I wrote the following code to Query this file
const aws = require('aws-sdk');
const s3 = new aws.S3();
const bucket = 'hotels.mserver.online';
const objectKey = 'hotelsrates.json';
exports.handler = (event,context,callback) => {
// TODO implement
const response = getS3Objects(bucket,objectKey); //s3.listObjectsV2({}).promise();
console.log(response);
};
function getS3Objects(bucket,key) {
return s3.getObject({ Bucket:bucket, Key:key, ResponseContentType:'application/json '})
.promise().then(file => { return file })
.catch(error => { return error });
}`
but the result is getting null .

Answer 1

I understand what you are trying to accomplish here but that is not the right way to do it.
function getS3Objects(bucket,key){
return s3.getObject({Bucket:bucket,Key:key,ResponseContentType:'application/json'})
.promise().then(file=>{return file})
.catch(error =>{return error});
}`
The part above will still return a promise object, which means that you need to handle it accordingly. Instead of const response = getS3Objects(bucket,objectKey); you want to do
getS3Objects(bucket,objectKey).then(response => console.log(response));
Inside of your handler function.
Furthermore, your usage of s3.getObject function is incorrect. Where first argument is an object - parameters, and the second argument is a callback function.
s3.getObject(params, function(err, data) {
if (err) console.log(err, err.stack); // an error occurred
else console.log(data);
Therefore in your case, you want to modify your getS3Objects function a bit. If you want to use promises, then you can do it like this.
function getS3Objects(bucket, key) {
return new Promise((resolve, reject) => {
s3.getObject(
{
Bucket: bucket,
Key: key,
ResponseContentType: 'application/json'
},
(err, data) => {
if (err) {
reject(err);
} else {
resolve(data);
}
}
);
});
}

Answer 2

Another way that you can do this is as follows:
const AWS = require('aws-sdk');
const s3 = new AWS.S3();
async function readFile(Bucket, Key) {
const params = {
Bucket,
Key,
ResponseContentType: 'application/json',
};
const f = await s3.getObject(params).promise();
return f.Body.toString('utf-8');
}
readFile('mybucket', 'xyz.json').then(console.log);