Question

尝试学习Hibernate，我正在尝试学习如何执行NamedQuries但是我正在考虑Exception in thread "main" org.hibernate.MappingException: Named query not known。请在这里帮助我

错误（仅消息，未显示完整堆栈）

Exception in thread "main" org.hibernate.MappingException: Named query not known: hibernate_tut_emp.Employee.FindCountOfNames
    at org.hibernate.internal.AbstractSessionImpl.getNamedQuery(AbstractSessionImpl.java:177)
    at org.hibernate.internal.SessionImpl.getNamedQuery(SessionImpl.java:1372)
    at hibernate_tut_emp.MyOps.main(MyOps.java:20)

Employee.java

package hibernate_tut_emp;

import java.io.Serializable;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

import javax.persistence.Table;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;



@Entity
@Table(name="Hib1")

@NamedQueries({
    @NamedQuery(name="GetDetailsByName" , query="select * from hib1 h where h.name=:name"),
    @NamedQuery(name="FindCountOfNames", query="select count(1) as cnt from hib1 h where h.name=:name")
})
public class Employee {
    private int id;
    private String name;

    @Id
    @Column(name="id")
    public int getId() {
        return id;
    }

    public void setId(int id) {
            this.id = id;
    }

    @Column(name="name")
    public String getName() {
            return name;
    }

    public void setName(String empName) {
            this.name = empName;
    }


}

MyOps.java

package hibernate_tut_emp;

import java.util.Scanner;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;

public class MyOps {

    public static void main(String[] args) {

        Scanner scnr = new Scanner(System.in);
        System.out.print("Enter a name : ");
        String name = scnr.next();

        SessionFactory ses = HibernateUtil.getSessionFactory();
        Session session = ses.openSession();

        Query query = session.getNamedQuery("hibernate_tut_emp.Employee.FindCountOfNames");


        query.setString("name", name);
        int count = ((Integer)query.iterate().next()).intValue();
        System.out.println("count : "+count);
    }
}

employee.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="hibernate_tut_emp.Employee" table="hib1">
        <id name="id" type="int" column="id">
            <generator class="native" />
        </id>
        <property name="name" type="string" column="name" />
    </class>
</hibernate-mapping>

hibernate.cfg.xml中

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
    <session-factory>
        <!-- Database connection settings -->
         <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
         <property name="connection.url">jdbc:mysql://localhost:3306/hibernate</property>
         <property name="connection.username">root</property>
         <property name="connection.password">mayank</property>

        <!-- JDBC connection pool (use the built-in) -->
         <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->
         <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

        <!-- Enable Hibernate's automatic session context management -->
          <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache -->
         <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
         <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
         <property name="hbm2ddl.auto">update</property>

      <mapping class="hibernate_tut_emp.Employee" />
      <mapping resource="employee.hbm.xml"/>

     </session-factory>
 </hibernate-configuration>

我搜索了所有可能但我认为我忽略了一些基本的东西。正确方向的任何迹象表示赞赏！：）

我考虑的一件事是，如果我在类文件NamedQueries中定义，我不需要在 xml 文件中提及它。如果我错了请纠正我！

Answer 1

这里有几个问题：

您的命名查询应使用实体而非表格。如果您想要原生查询，请改为使用NamedNativeQuery。

提取查询时无需提供实体名称。

改变这个：

Query query = session.getNamedQuery("hibernate_tut_emp.Employee.FindCountOfNames");

为：

Query query = session.getNamedQuery("FindCountOfNames");

MappingException：命名查询未知

1 个答案: