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HQL查询中的休眠表未映射错误

hibernate

我有一个使用Hibernate在数据库上进行CRUD操作的Web应用程序。我收到一条错误消息,说该表未映射。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;
    ...
}

我应该如何修改才能正常工作?


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2020-06-20

共1个答案

小编典典

异常消息怎么说?它说:

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

这告诉你什么?它告诉您Books未映射。也就是说,没有称为的映射类型Books

确实,没有。您的映射类型称为Book。它映射到名为的表Books,但类型称为Book。在编写HQL(或JPQL)查询时,您使用类型的名称,而不是表。

因此,将查询更改为:

select count(*) from Book

虽然我认为可能需要

select count(b) from Book b

如果HQL不支持该*表示法。

阅读异常消息可以学到很多东西!

2020-06-20