🧩 @RegisterForReflection example on Quarkus

Author: nzuguem

03-quarkus/src/main/java/me/nzuguem/quarkusnative/Hello.java

@@ -0,0 +1,12 @@
+package me.nzuguem.quarkusnative;
+
+import io.quarkus.runtime.annotations.RegisterForReflection;
+
+@RegisterForReflection
+public class Hello {
+    
+    // This piece of code must be evaluated during the initialisation phase at build-time
+    // The consequence is that System.currentTimeMillis() will be frozen in the resulting native image: This shows the use cases to be avoided with native images 
+    public final static String MESSAGE = "Hello from Reflection - " + System.currentTimeMillis();
+
+}

03-quarkus/src/main/java/me/nzuguem/quarkusnative/HelloController.java

@@ -10,6 +10,7 @@
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
+import java.util.List;
 import java.util.stream.Collectors;
 
 import io.quarkus.logging.Log;
@@ -51,4 +52,25 @@ public Response hello() {
             return Response.serverError().build();
         }
     }
+
+    @GET
+    @Path("from/reflection")
+    @Produces(MediaType.TEXT_PLAIN)
+    public Response helloFromReflection() {
+
+        try {
+            var className = List.<String>of("me", "nzuguem", "quarkusnative", "Hello")
+            .stream().collect(Collectors.joining("."));
+
+            var message = (String) Class.forName(className).getDeclaredField("MESSAGE").get(String.class);
+
+            return Response.ok(message).build();
+
+        } catch (IllegalArgumentException | IllegalAccessException | NoSuchFieldException | ClassNotFoundException exception) {
+
+            Log.error(exception.getMessage(), exception);
+
+            return Response.serverError().build();
+        }
+    }
 }