javajackson在序列化类型Object的if变量后保留类型信息

public class ClassA {
   private String id;
   private Object rawData;
}

public class ClassB {
   private String name;
}

C类

public class ClassC {
   String address;
}

主要类别

public class MainExample {
   public static void main( String[] args ) throws IOException {

      ObjectMapper mapper = new ObjectMapper(  );

      ClassB classB = new ClassB();
      //ClassC classC = new ClassC();
      ClassA classA = new ClassA();
      classA.setRawData(  classB );
      //classA.setRawData(  classC );

      if (classA.getRawData() instanceof ClassB) {
         System.out.println("true ");
      } else {
         System.out.println("false");
      }

      String classAString = mapper.writeValueAsString( classA );
      ClassA a = mapper.readValue( classAString, ClassA.class );

      if (a.getRawData() instanceof ClassB) {
         System.out.println("true ");
      } else {
         System.out.println("false");
      }
   }
}

“正确” 第二,如果不是打印的话 “错误” ??