HQL 查询中 Hibernate 表未映射错误

我有一个 Web 应用程序，它使用 Hibernate 对数据库进行 CRUD 操作。我收到一条错误消息，指出该表未映射。查看Java文件：

错误信息：

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 method:

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;
    ...
}

我应该如何修改它才能工作？

异常消息显示：

Books is not mapped [SELECT COUNT(*) FROM Books]; nested exception is org.hibernate.hql.ast.QuerySyntaxException: Books is not mapped [SELECT COUNT(*) FROM Books]

Books未映射。也就是说，没有名为的映射类型Books.

事实上，没有。您的映射类型称为Book。它映射到一个名为的表Books，但类型称为Book。当您编写 HQL（或 JPQL）查询时，您使用类型的名称，而不是表。

因此，将您的查询更改为：

select count(*) from Book

虽然我认为可能需要

select count(b) from Book b

如果HQL不支持*符号。