看CrudRepository接口，进去一看，说好的crud，可是怎么不见merge或update呢？
再一看save注释：
/** * Saves a given entity. Use the returned instance for further operations as the save operation might have changed the * entity instance completely. * * @param entity * @return the saved entity */ <S extends T> S save(S entity);
这。。。
点进去看一看有哪些实现。。。
只有SimpleJpaRepository中的实现：
/*
* (non-Javadoc)
* @see org.springframework.data.repository.CrudRepository#save(java.lang.Object)
*/
@Transactional
public <S extends T> S save(S entity) {
if (entityInformation.isNew(entity)) {
em.persist(entity);
return entity;
} else {
return em.merge(entity);
}
}