如何确定对象是否存在 AWS S3 Node.JS sdk
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How to determine if object exists AWS S3 Node.JS sdk
提问by Maurício Giordano
I need to check if a file exists using AWS SDK. Here is what I'm doing:
我需要使用 AWS SDK 检查文件是否存在。这是我在做什么：
var params = {
Bucket: config.get('s3bucket'),
Key: path
};
s3.getSignedUrl('getObject', params, callback);
It works but the problem is that when the object doesn't exists, the callback (with arguments err and url) returns no error, and when I try to access the URL, it says "NoSuchObject".
它有效，但问题是当对象不存在时，回调（带有参数 err 和 url）不返回错误，当我尝试访问 URL 时，它显示“NoSuchObject”。
Shouldn't this getSignedUrlmethod return an error object when the object doesn't exists? How do I determine if the object exists? Do I really need to make a call on the returned URL?
getSignedUrl当对象不存在时，这个方法不应该返回一个错误对象吗？如何判断对象是否存在？我真的需要调用返回的 URL 吗？
回答by CaptEmulation
Before creating the signed URL, you need to check if the file exists directly from the bucket. One way to do that is by requesting the HEAD metadata.
在创建签名 URL 之前，您需要直接从存储桶中检查文件是否存在。一种方法是请求 HEAD 元数据。
// Using callbacks
s3.headObject(params, function (err, metadata) {
if (err && err.code === 'NotFound') {
// Handle no object on cloud here
} else {
s3.getSignedUrl('getObject', params, callback);
}
});
// Using async/await (untested)
try {
const headCode = await s3.headObject(params).promise();
const signedUrl = s3.getSignedUrl('getObject', params);
// Do something with signedUrl
} catch (headErr) {
if (headErr.code === 'NotFound') {
// Handle no object on cloud here
}
}
回答by banoth ravinder
by using headObjectmethod
通过使用headObject方法
AWS.config.update({
accessKeyId: "*****",
secretAccessKey: "****",
region: region,
version: "****"
});
const s3 = new AWS.S3();
const params = {
Bucket: s3BucketName,
Key: "filename" //if any sub folder-> path/of/the/folder.ext
}
try {
await s3.headObject(params).promise()
console.log("File Found in S3")
} catch (err) {
console.log("File not Found ERROR : " + err.code)
}
As params are constant, the best way to use it with const. If the file is not found in the s3 it throws the error NotFound : null.
由于 params 是常量，因此最好将它与const. 如果在 s3 中找不到该文件，则会引发错误NotFound : null。
If you want to apply any operations in the bucket, you have to change the permissions of CORS Configurationin the respective bucket in the AWS. For changing permissions Bucket->permission->CORS Configurationand Add this code.
如果要在存储桶中应用任何操作，则必须更改CORS ConfigurationAWS 中相应存储桶中的权限。用于更改权限Bucket->permission->CORS Configuration并添加此代码。
<CORSConfiguration>
<CORSRule>
<AllowedOrigin>*</AllowedOrigin>
<AllowedMethod>PUT</AllowedMethod>
<AllowedMethod>POST</AllowedMethod>
<AllowedMethod>DELETE</AllowedMethod>
<AllowedMethod>GET</AllowedMethod>
<AllowedMethod>HEAD</AllowedMethod>
<AllowedHeader>*</AllowedHeader>
</CORSRule>
</CORSConfiguration>
for more information about CORS Configuration : https://docs.aws.amazon.com/AmazonS3/latest/dev/cors.html
有关 CORS 配置的更多信息：https: //docs.aws.amazon.com/AmazonS3/latest/dev/cors.html
回答by sky
The simplest solution without try/catch block.
没有 try/catch 块的最简单的解决方案。
const exists = await s3
.headObject({
Bucket: S3_BUCKET_NAME,
Key: s3Key,
})
.promise()
.then(
() => true,
err => {
if (err.code === 'NotFound') {
return false;
}
throw err;
}
);
回答by H6.
You can also use the waitFormethod together with the state objectExists. This will use S3.headObject()internally.
您也可以将waitFor方法与状态一起使用objectExists。这将在S3.headObject()内部使用。
var params = {
Bucket: config.get('s3bucket'),
Key: path
};
s3.waitFor('objectExists', params, function(err, data) {
if (err) console.log(err, err.stack); // an error occurred
else console.log(data); // successful response
});
回答by Amaynut
Use getObjectmethod like this:
使用getObject方法如下：
var params = {
Bucket: config.get('s3bucket'),
Key: path
};
s3.getObject(params, function(err, data){
if(err) {
console.log(err);
}else {
var signedURL = s3.getSignedUrl('getObject', params, callback);
console.log(signedURL);
}
});
回答by ABHAY JOHRI
Synchronous call on S3 in Nodejs instead of asynchronous call using Promise
在 Nodejs 中同步调用 S3 而不是使用 Promise 的异步调用
var request = require("request");
var AWS = require("aws-sdk");
AWS.config.update({
accessKeyId: "*****",
secretAccessKey: "********"
});
const s3 = new AWS.S3();
var response;
function initialize(bucket,key) {
// Setting URL and headers for request
const params = {
Bucket: bucket,
Key: key
};
// Return new promise
return new Promise(function(resolve, reject) {
s3.headObject(params, function(err, resp, body) {
if (err) {
console.log('Not Found : ' + params.Key );
reject(params.Key);
} else {
console.log('Found : ' + params.Key );
resolve(params.Key);
}
})
})
}
function main() {
var foundArray = new Array();
var notFoundArray = new Array();
for(var i=0;i<10;i++)
{
var key = '1234'+ i;
var initializePromise = initialize('****',key);
initializePromise.then(function(result) {
console.log('Passed for : ' + result);
foundArray.push(result);
console.log (" Found Array : "+ foundArray);
}, function(err) {
console.log('Failed for : ' + err);
notFoundArray.push(err);
console.log (" Not Found Array : "+ notFoundArray);
});
}
}
main();
回答by ABHAY JOHRI
Synchronous Put Operation
同步看跌操作
var request = require("request");
var AWS = require("aws-sdk");
AWS.config.update({
accessKeyId: "*****",
secretAccessKey: "***"
});
const s3 = new AWS.S3();
var response;
function initialize(bucket,key) {
// Setting URL and headers for request
const params = {
Bucket: bucket,
Key: key
};
// Return new promise
return new Promise(function(resolve, reject) {
s3.putObject(params, function(err, resp, body) {
if (err) {
reject();
} else {
resolve();
}
})
})
}
function main() {
var promiseArray = [];
var prefix = 'abc/test/';
for(var i=0;i<10;i++)
{
var key = prefix +'1234'+ i;
promiseArray[i] = initialize('bucket',key);
promiseArray[i].then(function(result) {
console.log (" Successful ");
}, function(err) {
console.log (" Error ");
});
}
console.log('Promises ' + promiseArray);
Promise.all(promiseArray).then(function(values) {
console.log("******TESTING****");
});
}
main();
回答by ABHAY JOHRI
Promise.All without failure Synchronous Operation
Promise.All 无失败同步操作
var request = require("request");
var AWS = require("aws-sdk");
AWS.config.update({
accessKeyId: "*******",
secretAccessKey: "***********"
});
const s3 = new AWS.S3();
var response;
function initialize(bucket,key) {
// Setting URL and headers for request
const params = {
Bucket: bucket,
Key: key
};
// Return new promise
return new Promise(function(resolve, reject) {
s3.headObject(params, function(err, resp, body) {
if (err) {
resolve(key+"/notfound");
} else{
resolve(key+"/found");
}
})
})
}
function main() {
var foundArray = new Array();
var notFoundArray = new Array();
var prefix = 'abc/test/';
var promiseArray = [];
try{
for(var i=0;i<10;i++)
{
var key = prefix +'1234' + i;
console.log("Key : "+ key);
promiseArray[i] = initialize('bucket',key);
promiseArray[i].then(function(result) {
console.log("Result : " + result);
var temp = result.split("/");
console.log("Temp :"+ temp);
if (temp[3] === "notfound")
{
console.log("NOT FOUND");
}else{
console.log("FOUND");
}
}, function(err) {
console.log (" Error ");
});
}
Promise.all(promiseArray).then(function(values) {
console.log("^^^^^^^^^^^^TESTING****");
}).catch(function(error) {
console.error(" Errro : "+ error);
});
}catch(err){
console.log(err);
}
}
main();
