JPA下的原生sql查询

最新推荐文章于 2024-07-31 00:13:48 发布

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本文深入探讨了使用Java Persistence API (JPA)和Hibernate框架进行数据库查询的多种方法，包括原生SQL查询、Criteria API及实体管理器的高级用法。通过具体示例，展示了如何实现复杂的关联表查询，并介绍了不同查询方式的优缺点。

private @Autowired EntityManager em;
//private @PersistenceContext EntityManager defaultEm;
@SuppressWarnings("unchecked")
public List<Book> findByName1(String bookName, String expressName) {
   String sql = "select * from t_book b left join t_express e on b.exp_id = e.id where "
           + "b.name like '" + bookName + "' and e.name like '" + expressName +"'";
   Query query = em.createNativeQuery(sql, Book.class);
   //query 有executeUpdate、getFirstResult等方法，可以根据sql调用
   List<Book> bookList = query.getResultList();
   return bookList;
}
//@Query(value="select * from t_book b left join t_express e on b.exp_id = e.id where "
//           + "b.name like ?1 and e.name like ?2", nativeQuery=true)
//List<Book> findByName(String bookName, String expressName);
public List<Book> findByName2(String bookName, String expressName) {
   return this.repository.findByName(bookName, expressName);
}

@SuppressWarnings("unchecked")
public List<BookExpress> findBookExpress1(String bookName, String expressName) {
   String sql = "select b.id as bookId,b.name as bookName, e.id as expressId, e.name as expressName from t_book b left join t_express e "
           + "on b.exp_id = e.id where b.name like '" + bookName + "' and e.name like '" + expressName +"'";
   //如果不设置自定义的ResultTransformer转换器，则Hibernate将每行返回结果的数据按照结果列的顺序装入Object数组中。
   //关联表映射的时候，每个字段都需要addScalar
   Query query = em.createNativeQuery(sql);
   List<BookExpress> result = query.unwrap(SQLQuery.class)
           .addScalar("bookId", LongType.INSTANCE).addScalar("bookName").addScalar("expressId", LongType.INSTANCE).addScalar("expressName")
           .setResultTransformer(Transformers.aliasToBean(BookExpress.class)).list();
   return result;
}

//注意sql里边的双引号转义
@SuppressWarnings("unchecked")
public List<BookExpress> findBookExpress2(String bookName, String expressName) throws IllegalAccessException, InvocationTargetException {
   String sql = "select b.id as \"bookId\",b.name as \"bookName\", e.id as \"expressId\", e.name as \"expressName\" from t_book b left join t_express e "
           + "on b.exp_id = e.id where b.name like '" + bookName + "' and e.name like '" + expressName +"'";
   Query query = em.createNativeQuery(sql);
   List<Map<String, Object>> resultList = query.unwrap(SQLQuery.class).setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP).list();
   if(CollectionUtils.isEmpty(resultList)) {
       return null;
   }
   List<BookExpress> result = new ArrayList<>(resultList.size());
   for(Map<String,Object> map : resultList) {
       BookExpress exp = new BookExpress();
       BeanUtils.populate(exp, map);
       result.add(exp);
   }
   return result;
}
//getDelegate不用事务就能获取到session，但是dowork查询的时候为什么报错（org.hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl@10cf3d8 is closed）
public List<BookExpress> findBookExpress3(String bookName, String expressName) {
   Session session = (Session)em.getDelegate();//为什么getDelegate不需要事物，unwrap需要事务
   //Session session = em.unwrap(Session.class);
   BookExpressQueryWork1 bookExpressQueryWork = new BookExpressQueryWork1();
   bookExpressQueryWork.setBookName(bookName);
   bookExpressQueryWork.setExpressName(expressName);

   session.doWork(bookExpressQueryWork);
   session.disconnect();
   return bookExpressQueryWork.getBookExpresses();
}