From 47dc6b96aefb1f153d027362bec8ab4999e9208c Mon Sep 17 00:00:00 2001
From: Joe Di Pol <joe.dipol@oracle.com>
Date: Thu, 21 Mar 2024 17:09:13 -0700
Subject: [PATCH] Update streaming example so it starts and downloads last
 uploaded file

---
 examples/webserver/streaming/README.md        | 13 ++++++---
 .../examples/webserver/streaming/Main.java    |  2 +-
 .../webserver/streaming/StreamingService.java | 27 ++++++++++++-------
 3 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/examples/webserver/streaming/README.md b/examples/webserver/streaming/README.md
index ca171f6c584..6ef6e9346a4 100644
--- a/examples/webserver/streaming/README.md
+++ b/examples/webserver/streaming/README.md
@@ -1,9 +1,14 @@
 # Streaming Example
 
-This application uses NIO and data buffers to show the implementation of a simple streaming service.
- Files can be uploaded and downloaded in a streaming fashion using `Subscriber<DataChunk>` and 
-`Producer<DataChunk>`. As a result, service runs in constant space instead of proportional
-to the size of the file being uploaded or downloaded.
+This application is an example of a very simple streaming service. It leverages the
+fact that Helidon uses virtual threads to perform simple input/output stream blocking
+operations in the endpoint handlers. As a result, this service runs in constant space instead
+of proportional to the size of the file being uploaded or downloaded.
+
+There are two endpoints:
+
+- `upload` : uploads a file to the service
+- `download` : downloads the previously uploaded file
 
 ## Build and run
 
diff --git a/examples/webserver/streaming/src/main/java/io/helidon/examples/webserver/streaming/Main.java b/examples/webserver/streaming/src/main/java/io/helidon/examples/webserver/streaming/Main.java
index 068d176669f..81a9c2627b1 100644
--- a/examples/webserver/streaming/src/main/java/io/helidon/examples/webserver/streaming/Main.java
+++ b/examples/webserver/streaming/src/main/java/io/helidon/examples/webserver/streaming/Main.java
@@ -25,7 +25,7 @@
  */
 public class Main {
 
-    static final String LARGE_FILE_RESOURCE = "/large-file.bin";
+    static final String LARGE_FILE_PATH = "target/classes/large-file.bin";
 
     private Main() {
     }
diff --git a/examples/webserver/streaming/src/main/java/io/helidon/examples/webserver/streaming/StreamingService.java b/examples/webserver/streaming/src/main/java/io/helidon/examples/webserver/streaming/StreamingService.java
index faac94da8ec..af50f95e858 100644
--- a/examples/webserver/streaming/src/main/java/io/helidon/examples/webserver/streaming/StreamingService.java
+++ b/examples/webserver/streaming/src/main/java/io/helidon/examples/webserver/streaming/StreamingService.java
@@ -16,6 +16,7 @@
 
 package io.helidon.examples.webserver.streaming;
 
+import java.io.File;
 import java.io.IOException;
 import java.io.UncheckedIOException;
 import java.net.URISyntaxException;
@@ -26,6 +27,7 @@
 import java.util.Objects;
 import java.util.logging.Logger;
 
+import io.helidon.http.Status;
 import io.helidon.webserver.http.HttpRules;
 import io.helidon.webserver.http.HttpService;
 import io.helidon.webserver.http.ServerRequest;
@@ -38,14 +40,13 @@
 public class StreamingService implements HttpService {
     private static final Logger LOGGER = Logger.getLogger(StreamingService.class.getName());
 
-    private final Path filePath;
+    // Last file uploaded (or default). Since we don't do any locking
+    // when operating on the file this example is not safe for concurrent requests.
+    private volatile File file;
 
     StreamingService() {
-        try {
-            filePath = Paths.get(Objects.requireNonNull(getClass().getResource(Main.LARGE_FILE_RESOURCE)).toURI());
-        } catch (URISyntaxException e) {
-            throw new RuntimeException(e);
-        }
+        // Default download file;
+        file = Paths.get(Main.LARGE_FILE_PATH).toFile();
     }
 
     @Override
@@ -59,22 +60,28 @@ private void upload(ServerRequest request, ServerResponse response) {
         try {
             Path tempFilePath = Files.createTempFile("large-file", ".tmp");
             Files.copy(request.content().inputStream(), tempFilePath, StandardCopyOption.REPLACE_EXISTING);
+            file = tempFilePath.toFile();
             response.send("File was stored as " + tempFilePath);
         } catch (IOException e) {
             throw new UncheckedIOException(e);
         }
-        LOGGER.info("Exiting upload ...");
+        LOGGER.info("Exiting upload after uploading " + file.length() + " bytes...");
     }
 
     private void download(ServerRequest request, ServerResponse response) {
         LOGGER.info("Entering download ..." + Thread.currentThread());
-        long length = filePath.toFile().length();
+        if (!file.canRead()) {
+            LOGGER.warning("Can't read file " + file.getAbsolutePath());
+            response.status(Status.INTERNAL_SERVER_ERROR_500).send();
+            return;
+        }
+        long length = file.length();
         response.headers().contentLength(length);
         try {
-            Files.copy(filePath, response.outputStream());
+            Files.copy(file.toPath(), response.outputStream());
         } catch (IOException e) {
             throw new UncheckedIOException(e);
         }
-        LOGGER.info("Exiting download ...");
+        LOGGER.info("Exiting download after serving " + length + " bytes...");
     }
 }