深入学习Spring Boot排查 @Transactional 引起的 NullPointerException问题

@Component
@Transactional
public class StudentDao {
 @Autowired
 private SqlSession sqlSession;
 public Student selectStudentById(long id) {
  return sqlSession.selectOne("selectStudentById", id);
 }
 public final Student finalSelectStudentById(long id) {
  return sqlSession.selectOne("selectStudentById", id);
 }
}

@PostConstruct
 public void init() {
  studentDao.selectStudentById(1);
  studentDao.finalSelectStudentById(1);
 }

Caused by: java.lang.NullPointerException
 at sample.mybatis.dao.StudentDao.finalSelectStudentById(StudentDao.java:27)
 at com.example.demo.transactional.nullpointerexception.DemoNullPointerExceptionApplication.init(DemoNullPointerExceptionApplication.java:30)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:498)
 at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleElement.invoke(InitDestroyAnnotationBeanPostProcessor.java:366)
 at org.springframework.beans.factory.annotation.InitDestroyAnnotationBeanPostProcessor$LifecycleMetadata.invokeInitMethods(InitDestroyAnnotationBeanPostProcessor.java:311)

System.err.println(studentDao.getClass());

class sample.mybatis.dao.StudentDao$$EnhancerBySpringCGLIB$$210b005d

$ jps
5907 DemoNullPointerExceptionApplication

sudo java -jar dumpclass.jar 5907 'sample.mybatis.dao.StudentDao*' /tmp/dumpresult

class StudentDao$$EnhancerBySpringCGLIB$$210b005d extends StudentDao

public final Student selectStudentById(long paramLong)
 {
 try
 {
  MethodInterceptor tmp4_1 = this.CGLIB$CALLBACK_0;
  if (tmp4_1 == null)
  {
  tmp4_1;
  CGLIB$BIND_CALLBACKS(this);
  }
  MethodInterceptor tmp17_14 = this.CGLIB$CALLBACK_0;
  if (tmp17_14 != null)
  {
  Object[] tmp29_26 = new Object[1];
  Long tmp35_32 = new java/lang/Long;
  Long tmp36_35 = tmp35_32;
  tmp36_35;
  tmp36_35.<init>(paramLong);
  tmp29_26[0] = tmp35_32;
  return (Student)tmp17_14.intercept(this, CGLIB$selectStudentById$0$Method, tmp29_26, CGLIB$selectStudentById$0$Proxy);
  }
  return super.selectStudentById(paramLong);
 }
 catch (RuntimeException|Error localRuntimeException)
 {
  throw localRuntimeException;
 }
 catch (Throwable localThrowable)
 {
  throw new UndeclaredThrowableException(localThrowable);
 }
 }