feat: Add headers, panic, echo and store utilities (#728)

src/ui/README.md

@@ -27,8 +27,13 @@ Several "utility" endpoints are provided with useful functionality for various s
 
 | Method | Name                           | Description                                                                 |
 | ------ | ------------------------------ | --------------------------------------------------------------------------- |
-| `GET`  | `/utility/stress/{iterations}` | Stress the CPU with the number of iterations increasing the CPU consumption |
 | `GET`  | `/utility/status/{code}`       | Returns HTTP response with given HTTP status code                           |
+| `GET`  | `/utility/headers`             | Print the HTTP headers of the inbound request                               |
+| `GET`  | `/utility/panic`               | Shutdown the application with an error code                                 |
+| `POST` | `/utility/echo`                | Write back the POST payload sent                                            |
+| `POST` | `/utility/store`               | Write the payload to a file and return a hash                               |
+| `GET`  | `/utility/store/{hash}`        | Return the payload from the file system previously written                  |
+| `GET`  | `/utility/stress/{iterations}` | Stress the CPU with the number of iterations increasing the CPU consumption |
 
 ## Running
 

src/ui/src/main/java/com/amazon/sample/ui/web/UtilityController.java

@@ -21,14 +21,35 @@
 import org.springframework.http.ResponseEntity;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RequestHeader;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.ResponseBody;
 
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Map;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.context.ApplicationContext;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+
 @Controller
 @RequestMapping("/utility")
 public class UtilityController {
 
+    private final ApplicationContext context;
+
+    public UtilityController(ApplicationContext context) {
+        this.context = context;
+    }
+
     @GetMapping("/stress/{iterations}")
     @ResponseBody
     public double stress(@PathVariable int iterations) {
@@ -51,4 +72,75 @@ private double monteCarloPi(int iterations) {
     public ResponseEntity<String> status(@PathVariable int code) {
         return ResponseEntity.status(code).body("OK");
     }
+
+    @GetMapping(value = "/headers", produces = MediaType.APPLICATION_JSON_VALUE)
+    public ResponseEntity<Map<String, List<String>>> statusHeaders(@RequestHeader HttpHeaders headers) {
+        return ResponseEntity.ok()
+            .body(headers);
+    }
+
+    @GetMapping("/panic")
+    public ResponseEntity<String> panic() {
+        Thread thread = new Thread(() -> {
+            try {
+                Thread.sleep(500); // Small delay to allow response to be sent
+                SpringApplication.exit(context, () -> 1);
+                System.exit(255);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+            }
+        });
+        thread.start();
+        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Shutting down...");
+    }
+
+    // function /echo that answer the hash provided as POST input
+    @PostMapping("/echo")
+    @ResponseBody
+    public ResponseEntity<String> echo(@RequestBody String body) {
+        return ResponseEntity.ok()
+            .body(body);
+    }
+
+    // function /store what take a POST hash to write to a locally created file
+    @PostMapping("/store")
+    @ResponseBody
+    public ResponseEntity<String> store(@RequestBody String body) {
+        String filename = String.valueOf(Math.abs(body.hashCode())); // ensure positive number
+        try (java.io.FileWriter fileWriter = new java.io.FileWriter("/tmp/" + filename + ".json")) {
+            fileWriter.write(body);
+            return ResponseEntity.ok()
+                .body("{\"hash\": \"" + filename + "\"}");
+        } catch (Exception e) {
+            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR)
+                .body("Error writing file: " + e.getMessage());
+        }
+    }
+
+    // function /store/{hash} that read a local hash file
+    @GetMapping("/store/{hash}")
+    @ResponseBody
+    public ResponseEntity<String> store_hash(@PathVariable String hash) {
+        // Validate hash format - only allow numeric characters
+        if (!hash.matches("^[0-9]+$")) {
+            return ResponseEntity.badRequest()
+                .body("Invalid hash format");
+        }
+
+        // Normalize the path and verify it's within the intended directory
+        Path filePath = Paths.get("/tmp", hash + ".json").normalize();
+        if (!filePath.startsWith("/tmp/")) {
+            return ResponseEntity.badRequest()
+                .body("Invalid path");
+        }
+
+        try {
+            String body = new String(Files.readAllBytes(filePath));
+            return ResponseEntity.ok()
+                .body(body);
+        } catch (Exception e) {
+            return ResponseEntity.status(HttpStatus.NOT_FOUND)
+                .body("Error reading file: " + e.getMessage());
+        }
+    }
 }