Fix #334: make BlackbirdModule java.io.Serializable (#335)

Author: cowtowncoder

android-record/src/main/java/tools/jackson/module/androidrecord/AndroidRecordModule.java

@@ -35,9 +35,11 @@
  *
  * @author Eran Leshem
  **/
-public class AndroidRecordModule extends SimpleModule
+public class AndroidRecordModule
+    extends SimpleModule
+    implements java.io.Serializable
 {
-  private static final long serialVersionUID = 1L;
+  private static final long serialVersionUID = 3L;
 
   static final class AndroidRecordNaming
     extends DefaultAccessorNamingStrategy
@@ -72,7 +74,7 @@ public String findNameForRegularGetter(AnnotatedMethod am, String name)
 
   static class AndroidRecordClassIntrospector extends BasicClassIntrospector
   {
-      private static final long serialVersionUID = 1L;
+      private static final long serialVersionUID = 3L;
 
       public AndroidRecordClassIntrospector() {
           super();
@@ -106,7 +108,7 @@ public BasicClassIntrospector forOperation(MapperConfig<?> config) {
 
   static class AndroidRecordAnnotationIntrospector extends AnnotationIntrospector
   {
-    private static final long serialVersionUID = 1L;
+    private static final long serialVersionUID = 3L;
 
     @Override
     public Version version() {

blackbird/src/main/java/tools/jackson/module/blackbird/BlackbirdModule.java

@@ -14,25 +14,77 @@
 import tools.jackson.module.blackbird.ser.BBSerializerModifier;
 
 public class BlackbirdModule extends JacksonModule
+    implements java.io.Serializable // @since 3.1
 {
-    private Function<Class<?>, Lookup> _lookups;
+    private static final long serialVersionUID = 3L;
+
+    // 13-Feb-2026, tatu: [blackbird#334] This is a mess due to need for
+    //    backwards-compatibility... but has to be
+
+    private final Supplier<MethodHandles.Lookup> _lookupSupplier;
+
+    private final Function<Class<?>, MethodHandles.Lookup> _lookupFunction;
 
     public BlackbirdModule() {
-        this(MethodHandles::lookup);
+        _lookupSupplier = null;
+        _lookupFunction = null;
+    }
+
+    /**
+     * @since 3.1 Use default (no-args) constructor and override
+     *    {@link #findLookupSupplier()}) instead.
+     */
+    @Deprecated // @since 3.1
+    public BlackbirdModule(Supplier<MethodHandles.Lookup> lookupS) {
+        _lookupSupplier = lookupS;
+        _lookupFunction = null;
     }
 
-    public BlackbirdModule(Function<Class<?>, MethodHandles.Lookup> lookups) {
-        _lookups = lookups;
+    /**
+     * @since 3.1 Use default (no-args) constructor and override
+     *  {@link #findLookup}) instead.
+     */
+    @Deprecated // @since 3.1
+    public BlackbirdModule(Function<Class<?>, MethodHandles.Lookup> lookupF) {
+        _lookupSupplier = null;
+        _lookupFunction = lookupF;
     }
 
-    public BlackbirdModule(Supplier<MethodHandles.Lookup> lookup) {
-        this(c -> {
+    /**
+     * Overridable method module uses to access {@code MethodHandles.Lookup} supplier;
+     * needed to keep module itself {@link java.io.Serializable}.
+     *
+     * @since 3.1
+     */
+    protected Function<Class<?>, Lookup> findLookup() {
+        if (_lookupFunction != null) {
+            return _lookupFunction;
+        }
+        return _wrapWithJdkClassCheck(findLookupSupplier());
+    }
+
+    /**
+     * Overridable method module uses to access {@code MethodHandles.Lookup} supplier
+     * used to create actual lookup {@code Function}
+     *
+     * @since 3.1
+     */
+    protected Supplier<MethodHandles.Lookup> findLookupSupplier() {
+        return (_lookupSupplier != null)
+                ? _lookupSupplier
+                : MethodHandles::lookup;
+        
+    }
+    
+    protected Function<Class<?>, Lookup> _wrapWithJdkClassCheck(Supplier<MethodHandles.Lookup> lookup)
+    {
+        return c -> {
             final String className = c.getName();
             return (className.startsWith("java.")
                     // 23-Apr-2021, tatu: [modules-base#131] "sun.misc" problematic too
                     || className.startsWith("sun.misc."))
                 ? null : lookup.get();
-        });
+        };
     }
 
     @Override
@@ -43,9 +95,10 @@ public void setupModule(SetupContext context)
         {
             return;
         }
+        Function<Class<?>, Lookup> lookup = findLookup();
         CrossLoaderAccess openSesame = new CrossLoaderAccess();
-        context.addDeserializerModifier(new BBDeserializerModifier(_lookups, openSesame));
-        context.addSerializerModifier(new BBSerializerModifier(_lookups, openSesame));
+        context.addDeserializerModifier(new BBDeserializerModifier(lookup, openSesame));
+        context.addSerializerModifier(new BBSerializerModifier(lookup, openSesame));
     }
 
     @Override

blackbird/src/test/java/tools/jackson/module/blackbird/BlackbirdModuleJDKSerializabilityTest.java

@@ -0,0 +1,86 @@
+package tools.jackson.module.blackbird;
+
+import java.io.*;
+
+import org.junit.jupiter.api.Test;
+
+import tools.jackson.databind.ObjectMapper;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class BlackbirdModuleJDKSerializabilityTest extends BlackbirdTestBase
+{
+    static class Point {
+        public int x, y;
+    }
+
+    // First: verify that newly constructed module (registered to Mapper)
+    // can be JDK serialized, deserialized
+    @Test
+    public void testMapperWithoutUse() throws Exception
+    {
+        ObjectMapper mapper = newBlackbirdMapper();
+        byte[] ser = jdkSerialize(mapper);
+        ObjectMapper m2 = jdkDeserialize(ser);
+        assertNotNull(m2);
+
+        // and that it can be used successfully
+        _serDeserPointWith(m2);
+    }
+
+    // 24-May-2020, tatu: Fine with 3.0
+    @Test
+    public void testMapperAfterUse() throws Exception
+    {
+        ObjectMapper mapper = newBlackbirdMapper();
+
+        // force use of mapper first
+        _serDeserPointWith(mapper);
+
+        // then freeze/thaw
+        byte[] ser = jdkSerialize(mapper);
+        ObjectMapper m3 = jdkDeserialize(ser);
+        assertNotNull(m3);
+
+        _serDeserPointWith(m3);
+    }
+
+    /*
+    /**********************************************************
+    /* Helper methods
+    /**********************************************************
+     */
+    
+    private void _serDeserPointWith(ObjectMapper mapper) throws Exception
+    {
+        final Point input = new Point();
+        byte[] rawPoint = mapper.writeValueAsBytes(input);
+        Point result = mapper.readValue(rawPoint, Point.class);
+        assertNotNull(result);
+        assertEquals(input.x, result.x);
+        assertEquals(input.y, result.y);
+    }
+
+    protected byte[] jdkSerialize(Object o) throws IOException
+    {
+        ByteArrayOutputStream bytes = new ByteArrayOutputStream(1000);
+        ObjectOutputStream obOut = new ObjectOutputStream(bytes);
+        obOut.writeObject(o);
+        obOut.close();
+        return bytes.toByteArray();
+    }
+
+    @SuppressWarnings("unchecked")
+    protected <T> T jdkDeserialize(byte[] raw) throws IOException
+    {
+        ObjectInputStream objIn = new ObjectInputStream(new ByteArrayInputStream(raw));
+        try {
+            return (T) objIn.readObject();
+        } catch (ClassNotFoundException e) {
+            fail("Missing class: "+e.getMessage());
+            return null;
+        } finally {
+            objIn.close();
+        }
+    }
+}

blackbird/src/test/java/tools/jackson/module/blackbird/BlackbirdTestBase.java

@@ -1,6 +1,5 @@
 package tools.jackson.module.blackbird;
 
-import java.lang.invoke.MethodHandles;
 import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 
@@ -217,7 +216,7 @@ protected static JsonMapper.Builder blackbirdMapperBuilder() {
     protected static JsonMapper.Builder mapperBuilder() {
         return JsonMapper.builder()
                 .polymorphicTypeValidator(new NoCheckSubTypeValidator())
-                .addModule(new BlackbirdModule(MethodHandles::lookup));
+                .addModule(new BlackbirdModule());
     }
 
     protected static JsonMapper newVanillaJSONMapper() {

blackbird/src/test/java/tools/jackson/module/blackbird/TestAccessFallback.java

@@ -1,7 +1,5 @@
 package tools.jackson.module.blackbird;
 
-import java.lang.reflect.Proxy;
-
 import tools.jackson.databind.ObjectMapper;
 
 import org.junit.jupiter.api.Test;

blackbird/src/test/java/tools/jackson/module/blackbird/TestVersions.java

@@ -1,7 +1,6 @@
 package tools.jackson.module.blackbird;
 
 import java.io.*;
-import java.lang.invoke.MethodHandles;
 
 import org.junit.jupiter.api.Test;
 
@@ -18,7 +17,7 @@ public class TestVersions extends BlackbirdTestBase
     @Test
     public void testMapperVersions() throws IOException
     {
-        BlackbirdModule module = new BlackbirdModule(c -> MethodHandles.lookup());
+        BlackbirdModule module = new BlackbirdModule();
         assertVersion(module);
     }
 

release-notes/VERSION

@@ -22,6 +22,11 @@ Active maintainers:
 === Releases ===
 ------------------------------------------------------------------------
 
+3.1.0 (not yet released)
+
+#334: (blackbird) `BlackbirdModule` does not implement `java.io.Serializable`
+ (reported by @waldemarmeier)
+
 3.1.0-rc1 (27-Jan-2026)
 
 #229: Add `jackson-module-spi-subtypes` module