fix(java): fix row encoder for private struct (#2469)

## What does this PR do?

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## Related issues

Closes #2439

## Does this PR introduce any user-facing change?

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issue](https://github.com/apache/fory/issues/new/choose) describing the
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- [ ] Does this PR introduce any public API change?
- [ ] Does this PR introduce any binary protocol compatibility change?

## Benchmark

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Author: chaokunyang

java/fory-core/src/main/java/org/apache/fory/type/TypeUtils.java

@@ -619,43 +619,38 @@ public static boolean isBean(TypeRef<?> typeRef, TypeResolutionContext ctx) {
         || ctx.getCustomTypeRegistry().isExtraSupportedType(typeRef)) {
       return false;
     }
-    // since we need to access class in generated code in our package, the class must be public
     // if ReflectionUtils.hasNoArgConstructor(cls) return false, we use Unsafe to create object.
-    if (Modifier.isPublic(cls.getModifiers())) {
-      // bean class can be static nested class, but can't be not a non-static inner class
-      if (cls.getEnclosingClass() != null && !Modifier.isStatic(cls.getModifiers())) {
-        return false;
-      }
-      TypeResolutionContext newTypePath = ctx.appendTypePath(typeRef);
-      if (cls == Object.class) {
-        // return false for typeToken that point to un-specialized generic type.
-        return false;
-      }
-      boolean maybe =
-          !SUPPORTED_TYPES.contains(typeRef)
-              && !typeRef.isArray()
-              && !cls.isEnum()
-              && !ITERABLE_TYPE.isSupertypeOf(typeRef)
-              && !MAP_TYPE.isSupertypeOf(typeRef);
-      if (maybe) {
-        for (Descriptor d : Descriptor.getDescriptors(cls)) {
-          TypeRef<?> t = d.getTypeRef();
-          // do field modifiers and getter/setter validation here, not in getDescriptors.
-          // If Modifier.isFinal(d.getModifiers()), use reflection
-          // private field that doesn't have getter/setter will be handled by reflection.
-          TypeRef<?> replacementType =
-              ctx.getCustomTypeRegistry().replacementTypeFor(cls, t.getRawType());
-          if (replacementType != null) {
-            t = replacementType;
-          }
-          if (!isSupported(t, newTypePath)) {
-            return false;
-          }
+    // bean class can be static nested class, but can't be not a non-static inner class
+    if (cls.getEnclosingClass() != null && !Modifier.isStatic(cls.getModifiers())) {
+      return false;
+    }
+    TypeResolutionContext newTypePath = ctx.appendTypePath(typeRef);
+    if (cls == Object.class) {
+      // return false for typeToken that point to un-specialized generic type.
+      return false;
+    }
+    boolean maybe =
+        !SUPPORTED_TYPES.contains(typeRef)
+            && !typeRef.isArray()
+            && !cls.isEnum()
+            && !ITERABLE_TYPE.isSupertypeOf(typeRef)
+            && !MAP_TYPE.isSupertypeOf(typeRef);
+    if (maybe) {
+      for (Descriptor d : Descriptor.getDescriptors(cls)) {
+        TypeRef<?> t = d.getTypeRef();
+        // do field modifiers and getter/setter validation here, not in getDescriptors.
+        // If Modifier.isFinal(d.getModifiers()), use reflection
+        // private field that doesn't have getter/setter will be handled by reflection.
+        TypeRef<?> replacementType =
+            ctx.getCustomTypeRegistry().replacementTypeFor(cls, t.getRawType());
+        if (replacementType != null) {
+          t = replacementType;
+        }
+        if (!isSupported(t, newTypePath)) {
+          return false;
         }
-        return true;
-      } else {
-        return false;
       }
+      return true;
     } else {
       return false;
     }

java/fory-format/src/main/java/org/apache/fory/format/encoder/RowEncoderBuilder.java

@@ -184,7 +184,7 @@ public String genCode() {
   @Override
   public Expression buildEncodeExpression() {
     Reference inputObject = new Reference(ROOT_OBJECT_NAME, TypeUtils.OBJECT_TYPE, false);
-    Expression bean = new Expression.Cast(inputObject, beanType, ctx.newName(beanClass));
+    Expression bean = tryCastIfPublic(inputObject, beanType);
     Reference writer = new Reference(ROOT_ROW_WRITER_NAME, rowWriterTypeToken, false);
     Reference schemaExpr = new Reference(SCHEMA_NAME, schemaTypeToken, false);
 

java/fory-format/src/test/java/org/apache/fory/format/encoder/RowEncoderTest.java

@@ -19,6 +19,7 @@
 
 package org.apache.fory.format.encoder;
 
+import static org.apache.fory.collection.Collections.ofHashMap;
 import static org.apache.fory.format.encoder.CodecBuilderTest.testStreamingEncode;
 
 import com.google.common.collect.ImmutableMap;
@@ -101,4 +102,20 @@ public void testImportInnerClass() {
     Foo deserializedFoo = encoder.fromRow(row);
     Assert.assertEquals(foo, deserializedFoo);
   }
+
+  private static class PrivateStruct {
+    java.util.Map<Long, Long> f1;
+    java.util.Map<String, String> f2;
+  }
+
+  @Test
+  public void testPrivateBean() {
+    RowEncoder<PrivateStruct> encoder = Encoders.bean(PrivateStruct.class);
+    PrivateStruct s = new PrivateStruct();
+    s.f1 = ofHashMap(10L, 100L);
+    s.f2 = ofHashMap("k", "v");
+    PrivateStruct s1 = encoder.decode(encoder.encode(s));
+    Assert.assertEquals(s1.f1, s.f1);
+    Assert.assertEquals(s1.f2, s.f2);
+  }
 }