问题描述
我有一个Web应用程序,该应用程序使用Hibernate对数据库进行CRUD操作.我收到一条错误消息,说该表未映射.查看Java文件:
I have a web application that use Hibernate to make CRUD operations over a database. I got an error saying that the table is not mapped. See the Java files:
错误消息:
org.springframework.orm.hibernate3.HibernateQueryException: Books is not mapped [SELECT COUNT(*) FROM Books]; nested exception is org.hibernate.hql.ast.QuerySyntaxException: Books is not mapped [SELECT COUNT(*) FROM Books]
at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:660)
at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412)
at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:411)
...
Caused by: org.hibernate.hql.ast.QuerySyntaxException: Books is not mapped [SELECT COUNT(*) FROM Books]
at org.hibernate.hql.ast.util.SessionFactoryHelper.requireClassPersister(SessionFactoryHelper.java:181)
at org.hibernate.hql.ast.tree.FromElementFactory.addFromElement(FromElementFactory.java:111)
at org.hibernate.hql.ast.tree.FromClause.addFromElement(FromClause.java:93)
...
这是我的DAO.java
方法:
public int getTotalBooks(){
return DataAccessUtils.intResult(hibernateTemplate.find(
"SELECT COUNT(*) FROM Books"));
}
Book.java
:
@Entity
@Table(name="Books")
public class Book {
@Id
@GeneratedValue
@Column(name="id")
private int id;
@Column(name="title", nullable=false)
private String title;
...
}
如何修改才能正常工作?
How should I modify it in order to work?
推荐答案
该异常消息说什么?它说:
What does the exception message say? It says:
这说明了什么?它告诉您Books
未映射.也就是说,没有名为Books
的映射类型.
What does that tell you? It tell you that Books
is not mapped. That is, that there is no mapped type called Books
.
实际上,没有.您的映射类型称为Book
.它映射到名为Books
的表,但类型称为Book
.在编写HQL(或JPQL)查询时,您使用的是类型的名称,而不是表.
And indeed, there isn't. Your mapped type is called Book
. It's mapped to a table called Books
, but the type is called Book
. When you write HQL (or JPQL) queries, you use the names of the types, not the tables.
因此,将查询更改为:
尽管我认为可能需要
如果HQL不支持*
表示法.
If HQL doesn't support the *
notation.
从阅读异常消息中您可以学到很多东西!
There's a lot you can learn from reading exception messages!
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