added a Java example for creating an S3 Object Lambda

[sobrab]

This PR adds a Java example for creating an S3 Object Lambda.

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[kaiz-io]

🚀

[sobrab]

Including what?

[sobrab]

This should be replaced by:

public void handleRequest(S3ObjectLambdaEvent event, Context context) throws IOException, InterruptedException {
  // the rest of the code
}

The catch block should be removed.

[sobrab]

This client is never closed. This line of code should be removed from here and the client should be created in the statement of the try block. So this code:

try (var s3Client = S3Client.create()) {
  // the rest of the code
}

should be replaced with this:

try (
  var s3Client = S3Client.create();
  var httpClient = HttpClient.newBuilder().build()
) {
  // the rest of the code
}

This will ensure that the httpClient is closed automatically.

[sobrab]

The way it is now, this catch block is useless. It does not actually handle the exceptions caught. So it can be removed altogether. Obviously, the handleRequest method would then have to declare the 2 checked exceptions. Something like this:

  public void handleRequest(S3ObjectLambdaEvent event, Context context) throws IOException, InterruptedException {
    try (
      var s3Client = S3Client.create();
      var httpClient = HttpClient.newBuilder().build()
    ) {
      // the rest of the code
    } // no more catch block here

Or, the catch block could actually handle the exceptions caught by doing the following:

• log the exception so that it shows up in CloudWatch (this way you have more details later on about what went wrong);
• send a response to the S3 Object Lambda with a 500 statusCode for Internal Server Error and the corresponding errorCode and errorMessage.

[sobrab]

This comment is wrong and it should be removed. The message is not prefixed with the request ID. The request ID will not show up in the CloudWatch logs.

[sobrab]

Hi @kaiz-io,

I believe that some things were overlooked. I don't know how to handle it though since the PR is already merged. However, I figured I should point out what I've noticed. Also, some of the comments are a bit excessive don't you think? I understand this is an example/tutorial but for the most part the code is self-explanatory. Is it really necessary to say that a method called md5Hex will calculate the MD5 hash? Or that a method called runtime will set the runtime? Perhaps all the comments should be double-checked. Anyway, just my 2 cents. Hope you don't mind. And please, do let me know if you need anything else from me related to this PR.

Bye.