Add test to reproduce #285 (#289)

Author: apoorvam

blackbird/src/main/java/com/fasterxml/jackson/module/blackbird/CrossLoaderAccess.java

@@ -106,7 +106,8 @@ private static boolean hasFullAccess(MethodHandles.Lookup lookup) {
 
     private static Class<?> accessClassIn(MethodHandles.Lookup lookup) throws IOException, ReflectiveOperationException {
         Package pkg = lookup.lookupClass().getPackage();
-        String accessClassName = pkg.getName() + "." + CLASS_NAME;
+        final String pkgName = pkg.getName();
+        String accessClassName = pkgName.isEmpty() ? CLASS_NAME : (pkgName + "." + CLASS_NAME);
         ClassLoader lookupClassLoader = lookup.lookupClass().getClassLoader();
         try {
             return Class.forName(accessClassName, true, lookupClassLoader);
@@ -115,9 +116,9 @@ private static Class<?> accessClassIn(MethodHandles.Lookup lookup) throws IOExce
             try {
                 return Class.forName(accessClassName, true, lookupClassLoader);
             } catch (ClassNotFoundException ign) { }
-            String fqcn = pkg.getName()
-                    .replace('.', '/')
-                + "/" + CLASS_NAME;
+            String fqcn = pkgName.isEmpty() ? CLASS_NAME
+                    : (pkgName.replace('.', '/') + "/" + CLASS_NAME);
+
             ByteArrayOutputStream classBytes = new ByteArrayOutputStream(HEADER.length + FOOTER.length + fqcn.length() + 16);
             DataOutputStream dataOut = new DataOutputStream(classBytes);
             for (int b : HEADER) {

blackbird/src/test/java/com/fasterxml/jackson/module/blackbird/ser/TestNoPackageSerialization.java

@@ -0,0 +1,78 @@
+package com.fasterxml.jackson.module.blackbird.ser;
+
+import java.io.File;
+import java.lang.reflect.Field;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Arrays;
+
+import org.junit.jupiter.api.Test;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.module.blackbird.BlackbirdTestBase;
+
+import javax.tools.*;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class TestNoPackageSerialization extends BlackbirdTestBase
+{
+    @Test
+    public void testSerializeDeserializeDefaultPackageClass() throws Exception {
+        // Define the source code for a class in the default package (no package
+        // declaration)
+        String source = "package dynamicClassTest;" +
+                "public class Person {" +
+                "    public String name;" +
+                "    public int age;" +
+                "    public Person() {}" +
+                "    public Person(String name, int age) {" +
+                "        this.name = name;" +
+                "        this.age = age;" +
+                "    }" +
+                "}";
+
+        // Create a temporary directory for the compiled class
+        Path tempDir = Files.createTempDirectory("dynamicClassTest");
+        File sourceFile = new File(tempDir.toFile(), "Person.java");
+        //System.out.println(sourceFile.getAbsolutePath());
+        Files.write(sourceFile.toPath(), source.getBytes(StandardCharsets.UTF_8));
+
+        // Compile the source file using the JDK compiler
+        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
+        StandardJavaFileManager fileManager = compiler.getStandardFileManager(null, null, null);
+        Iterable<? extends JavaFileObject> compilationUnits = fileManager.getJavaFileObjects(sourceFile);
+        JavaCompiler.CompilationTask task = compiler.getTask(
+                null, fileManager, null,
+                Arrays.asList("-d", tempDir.toString()),
+                null, compilationUnits);
+        assertTrue(task.call(), "Compilation failed");
+        fileManager.close();
+
+        // Load the compiled class using a URLClassLoader
+        try (URLClassLoader classLoader = new URLClassLoader(new URL[] { tempDir.toUri().toURL() })) {
+            Class<?> personClass = classLoader.loadClass("dynamicClassTest.Person");
+
+            // Instantiate the Person object using reflection
+            Object personInstance = personClass.getConstructor(String.class, int.class)
+                    .newInstance("John Doe", 42);
+            final ObjectMapper mapper = newObjectMapper();
+
+            // Perform serialization and deserialization
+            String json = mapper.writeValueAsString(personInstance);
+            Object deserialized = mapper.readValue(json, personClass);
+
+            // Verify that the deserialized object has the expected field values via
+            // reflection
+            Field nameField = personClass.getField("name");
+            Field ageField = personClass.getField("age");
+
+            assertEquals("John Doe", nameField.get(deserialized));
+            assertEquals(42, ageField.get(deserialized));
+        }
+    }
+}

release-notes/CREDITS-2.x

@@ -160,3 +160,9 @@ Jack Dunning (@JDUNNIN)
 * Contributed #251: Constructor is not recognized when a record uses both arrays
   and generic types
  (2.18.0)
+
+Apoorva Manjunath (@apoorvam)
+
+* Reported, contributed fix for #285: `JacksonBlackbirdAccess` Class access
+  exception with Groovy Script serialization using `BlackbirdModule`
+ (2.19.0)

release-notes/VERSION-2.x

@@ -27,6 +27,9 @@ Active maintainers:
 
 #268: Unify testing structure/tools [JSTEP-10]
  (contributed by Joo-Hyuk K)
+#285: `JacksonBlackbirdAccess` Class access exception with Groovy Script
+  serialization using `BlackbirdModule`
+ (reported, fix contributed by Apoorva M)
 
 2.18.3 (28-Feb-2025)
 2.18.2 (27-Nov-2024)