我正在开发一个使用 Spring MVC 和 JPA 的 Web 项目，它是使用 MAVEN 构建的。不知何故，我不确定我是否正确完成了 JPA 配置，因为我在启动网络时遇到了这个错误
Caused by: org.hibernate.hql.internal.ast.QuerySyntaxException: User is not mapped [from User]
我以这种方式在 MYSQL 中创建了表：
mysql> desc users;
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| username | varchar(10) | NO | PRI | | |
| password | varchar(32) | YES | | NULL | |
| enabled | int(11) | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
我以这种方式声明了用户实体：
@Entity
@Table(name="users")
public class User {
@Id
@Column(name="username")
private String username;
@Column(name="password")
private String password;
@Column(name="enabled")
private Integer enabled;
我有这个配置datasource.xml：
<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/test"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</bean>
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="jpaVendorAdapter" ref="jpaVendorAdapter" />
<property name="dataSource" ref="dataSource"/>
<property name="packagesToScan" value="org.huahsin.ProjectA.*" />
</bean>
<bean id="jpaVendorAdapter" class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="databasePlatform" value="org.hibernate.dialect.MySQLInnoDBDialect" />
<property name="showSql" value="true" />
</bean>
这就是 DAO 将如何调用持久对象：
@Repository
public class UserDao implements IUserDao {
@PersistenceUnit
private EntityManagerFactory emf;
public User findByUsername(String username) {
List<User> l = (List<User>) emf.createEntityManager().createQuery("from User");
...
}
}