Javascript 如何使用 lambda 函数从 AWS s3 获取文本文件的内容？

How to get contents of a text file from AWS s3 using a lambda function?

提问by jstnchng

I was wondering if I could set up a lambda function for AWS, triggered whenever a new text file is uploaded into an s3 bucket. In the function, I would like to get the contents of the text file and process it somehow. I was wondering if this was possible...?

我想知道是否可以为 AWS 设置一个 lambda 函数，每当一个新的文本文件上传到 s3 存储桶时就会触发。在函数中，我想获取文本文件的内容并以某种方式对其进行处理。我想知道这是否可能......？

For example, if I upload foo.txt, with contents foobarbaz, I would like to somehow get foobarbaz in my lambda function so I can do stuff with it. I know I can get metadata from getObject, or a similar method.

例如，如果我上传内容为 foobarbaz 的 foo.txt，我想以某种方式在我的 lambda 函数中获取 foobarbaz，以便我可以用它做一些事情。我知道我可以从 getObject 或类似的方法获取元数据。

Thanks!

谢谢！

回答by jarmod

The S3 object key and bucket name are passed into your Lambda function via the eventparameter. You can then get the object from S3 and read its contents.

S3 对象键和存储桶名称通过事件参数传递到您的 Lambda 函数中。然后，您可以从 S3 获取对象并读取其内容。

Basic code to retrieve bucket and object key from the Lambda eventis as follows:

从 Lambda 检索存储桶和对象键的基本代码event如下：

exports.handler = function(event, context, callback) {
   var src_bkt = event.Records[0].s3.bucket.name;
   var src_key = event.Records[0].s3.object.key;
};

Once you have the bucket and key, you can call getObject to retrieve the object:

获得存储桶和密钥后，您可以调用 getObject 来检索对象：

var AWS = require('aws-sdk');
var s3 = new AWS.S3();

exports.handler = function(event, context, callback) {

    // Retrieve the bucket & key for the uploaded S3 object that
    // caused this Lambda function to be triggered
    var src_bkt = event.Records[0].s3.bucket.name;
    var src_key = event.Records[0].s3.object.key;

    // Retrieve the object
    s3.getObject({
        Bucket: src_bkt,
        Key: src_key
    }, function(err, data) {
        if (err) {
            console.log(err, err.stack);
            callback(err);
        } else {
            console.log("Raw text:\n" + data.Body.toString('ascii'));
            callback(null, null);
        }
    });
};

Here's an updated JavaScript example using ES6-style code and promises, minus error-handling:

这是一个使用 ES6 样式代码和 promise 的更新 JavaScript 示例，减去错误处理：

const AWS = require('aws-sdk');
const s3 = new AWS.S3();

exports.handler = async (event, context) => {
  const Bucket = event.Records[0].s3.bucket.name;
  const Key = event.Records[0].s3.object.key;
  const data = await s3.getObject({ Bucket, Key }).promise();
  console.log("Raw text:\n" + data.Body.toString('ascii'));
};

A number of posters have asked for the equivalent in Java, so here's an example:

许多海报要求 Java 中的等价物，所以这里有一个例子：

package example;

import java.net.URLDecoder;

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;
import com.amazonaws.services.lambda.runtime.events.S3Event;
import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.AmazonS3Client;
import com.amazonaws.services.s3.event.S3EventNotification.S3EventNotificationRecord;

public class S3GetTextBody implements RequestHandler<S3Event, String> {

    public String handleRequest(S3Event s3event, Context context) {
        try {
            S3EventNotificationRecord record = s3event.getRecords().get(0);

            // Retrieve the bucket & key for the uploaded S3 object that
            // caused this Lambda function to be triggered
            String bkt = record.getS3().getBucket().getName();
            String key = record.getS3().getObject().getKey().replace('+', ' ');
            key = URLDecoder.decode(key, "UTF-8");

            // Read the source file as text
            AmazonS3 s3Client = new AmazonS3Client();
            String body = s3Client.getObjectAsString(bkt, key);
            System.out.println("Body: " + body);
            return "ok";
        } catch (Exception e) {
            System.err.println("Exception: " + e);
            return "error";
        }
    }
}

回答by jaywalker

You can use data.Body.toString('ascii')to get the contents of the text file, assuming that the text file was encoded used ascii format. You can also pass other encoding types to the function. Check out Node-Bufferfor further details.

您可以使用data.Body.toString('ascii')来获取文本文件的内容，假设文本文件是使用 ascii 格式编码的。您还可以将其他编码类型传递给函数。查看节点缓冲区以获取更多详细信息。

回答by Shubham Bansal

I am using lambda function with a python 3.6 environment. The code below will read the contents of a file main.txt inside bucket my_s3_bucket. Make sure to replace name of bucket and file name according to your needs.

我在 python 3.6 环境中使用 lambda 函数。下面的代码将读取存储桶 my_s3_bucket 中文件 main.txt 的内容。确保根据您的需要替换存储桶名称和文件名。

def lambda_handler(event, context):
    # TODO implement
    import boto3

    s3 = boto3.client('s3')
    data = s3.get_object(Bucket='my_s3_bucket', Key='main.txt')
    contents = data['Body'].read()
    print(contents)