java Hibernate SQLQuery - 按名称获取对象
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Hibernate SQLQuery - Get Object by name
提问by wilson
I have a method to get a Category by its "id" and I need a similar method to get a Category by its "name". I did these methods by using Hibernate. How can I fix my second method to get a Category by name? My source code is as follow:
我有一种通过“id”获取类别的方法，我需要一个类似的方法来通过“名称”获取类别。我使用 Hibernate 完成了这些方法。如何修复我的第二种方法以按名称获取类别？我的源代码如下：
// It works
@Override
public Category getById(int id) {
return (Category) sessionFactory.getCurrentSession().get(Category.class, id);
}
// It doesn't works
@Override
public Category getByName(String name) {
return (Category) sessionFactory.getCurrentSession().
createSQLQuery("SELECT FROM Category WHERE name="+name);
}
I have this error with the second method:
第二种方法我有这个错误：
java.lang.ClassCastException: org.hibernate.impl.SQLQueryImpl cannot be cast to com.sedae.model.Category
java.lang.ClassCastException: org.hibernate.impl.SQLQueryImpl 不能转换为 com.sedae.model.Category
These are my controllers.
这些是我的控制器。
@RequestMapping(value = "/getCategoryById/{id}")
public String getCategoryById(Model model, @PathVariable ("id") int id){
model.addAttribute("category", categoryService.getById(id));
return "/getCategoryById";
}
@RequestMapping(value = "/getCategoryByName/{name}")
public String getCategoryByName(Model model, @PathVariable("name") String name){
model.addAttribute("category", categoryService.getByName(name));
return "/getCategoryByName";
}
Thanks in advance people.
在此先感谢人们。
回答by user3487063
If you are sure you have only one entry per category name in your table then you can use Query#uniqueResult:
如果您确定表中每个类别名称只有一个条目，那么您可以使用Query#uniqueResult：
Query query= sessionFactory.getCurrentSession().
createQuery("from Category where name=:name");
query.setParameter("name", name);
Category category = (Category) query.uniqueResult();
Make sure to handle the exceptions thrown by uniqueResult.
确保处理由 uniqueResult 抛出的异常。
