使用Amazon Java SDK S3的putObject后，是否需关闭传入的InputStream？

Great question — this is one of those edge cases where the docs are a bit silent, but let's break this down clearly:

Short Answer #

Yes, you absolutely should manually close the InputStream you pass to putObject, or better yet, use Java's try-with-resources pattern to handle it automatically.

Why This Matters #

1. Java's Resource Management Convention
   In Java, the unwritten rule is: whoever creates a resource is responsible for closing it. When you pass your own InputStream to the SDK, the SDK doesn't assume ownership of that resource. The official examples use File because when you pass a File to putObject, the SDK creates the underlying FileInputStream itself and can safely close it. But for streams you create, that responsibility falls back to you.

2. SDK Behavior Isn't Guaranteed
   While some versions of the S3 SDK might attempt to close the stream after a successful upload, this isn't a documented guarantee. If the upload fails mid-process (e.g., network error, invalid bucket permissions), the SDK might not execute the cleanup logic, leaving your stream open and causing resource leaks — like stuck connections, exhausted memory, or blocked file handles.

3. Try-With-Resources Is Foolproof
   The safest way to handle this is to wrap your InputStream in a try-with-resources block, which ensures the stream is closed automatically whether the upload succeeds or fails. Here's a concrete example:

// Safe way to handle InputStream with putObject
try (InputStream myStream = new ByteArrayInputStream(myContent.getBytes())) {
    PutObjectRequest request = PutObjectRequest.builder()
            .bucket("my-target-bucket")
            .key("my-object-key")
            .build();
    
    s3Client.putObject(request, RequestBody.fromInputStream(myStream, myContent.length()));
} catch (IOException | S3Exception e) {
    // Handle your errors here
}

What If I Don't Close It? #

Depending on the type of stream, you could run into issues like:

• Network streams holding open connections, exhausting your connection pool
• File streams locking files on disk (preventing deletion or modification)
• Memory-based streams causing unnecessary memory bloat until garbage collection kicks in

Don't rely on the SDK to clean up after you — take control of your resource lifecycle.

内容的提问来源于stack exchange，提问作者Wim Deblauwe