Hibernate的命名查询（NamedQuery）

把HQL语句或SQL语句写在Hibernate实体类对应的映射文件中的使用。

打开Hibernate的Session的源码，我们可以看到有一个getNamedQuery(String name);的方法，如下：

/**
     * Obtain an instance of <tt>Query</tt> for a named query string defined in the
     * mapping file.
     *
     * @param queryName the name of a query defined externally
     * @return Query
     * @throws HibernateException
     */
    public Query getNamedQuery(String queryName) throws HibernateException;

这个方法就是可以执行定义在Hibernate实体类映射文件中的HQL或Sql语句。

具体做法下面我一一讲解，首先测试在映射文件中定义HQL语句。

我在User实体类的映射文件中定义了一个name为getUserByName的HQL查询语句，代码如下：

<? xml version = "1.0" ?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "D:\tools\hibernate\dtd\hibernate-mapping-3.0.dtd">
< hibernate-mapping
    package = "com.xigua.domain" >
    < class name = "User" >
        < id name = "id" >
            < generator class = "native" />
        </ id >
        < property name = "name" />
        < property name = "birthday" />
    </ class >

    <!-- 定义一个查询，名称为getUserByName -->
    < query name = "getUserByName" >
        <![CDATA[from User where name = :name]]>
    </ query >
</ hibernate-mapping >

然后编写测试类使用Session中的getNamedQuery(String name)方法进行测试，代码如下：

package com.xigua.test;

import java.util.Date;
import java.util.List;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.xigua.domain.User;
import com.xigua.utils.HibernateUtil;

public class Test9 {

    public static void main(String[] args) {
        addUser();
        String name = "xigua" ;
        List<User> list = namedQuery(name);
        if (list != null && !list.isEmpty()) {
            for (User user : list) {
                System.out.println(user.getId() + ", " + user.getName() + ", " + user.getBirthday());
            }
        }
    }

    public static void addUser() {
        Session session = null ;
        Transaction tx = null ;
        try {
            session = HibernateUtil.getSession();
            tx = session.beginTransaction();
            User user = new User();
            user.setName( "xigua" );
            user.setBirthday( new Date());
            session.save(user);

            user = new User();
            user.setName( "donggua" );
            user.setBirthday( new Date());
            session.save(user);
            tx.commit();
        } catch (Exception e) {
            if (tx != null ) {
                tx.rollback();
            }
        } finally {
            if (session != null ) {
                session.close();
            }
        }
    }

    public static List<User> namedQuery(String name) {
        Session session = null ;
        try {
            session = HibernateUtil.getSession();
            Query query = session.getNamedQuery( "getUserByName" );
            query.setParameter( "name" , name);
            return query.list();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (session != null ) {
                session.close();
            }
        }

        return null ;
    }

}

在映射文件中除了可以定义HQL语句，也还是可以定义Sql语句的。

前面的User实体类的映射文件修改如下：

<? xml version = "1.0" ?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "D:\tools\hibernate\dtd\hibernate-mapping-3.0.dtd">
< hibernate-mapping
    package = "com.xigua.domain" >
    < class name = "User" >
        < id name = "id" >
            < generator class = "native" />
        </ id >
        < property name = "name" />
        < property name = "birthday" />
    </ class >

    <!-- 定义一个查询，名称为getUserByName
    <query name="getUserByName">
        <![CDATA[from User where name = :name]]>
    </query>
    -->

    < sql-query name = "getUserByName" >
        <![CDATA[select id, name from user where name = :name]]>
    </ sql-query >
</ hibernate-mapping >

测试代码如下：

 

package com.xigua.test;

import java.util.Date;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.xigua.domain.User;
import com.xigua.utils.HibernateUtil;

public class Test10 {

    public static void main(String args[]) {
        addUser();
        String name = "xigua" ;
        User user = namedSqlQuery(name);
        if (user != null ) {
            System.out.println(user.getId() + ", " + user.getName());
        }

    }

    public static void addUser() {
        Session session = null ;
        Transaction tx = null ;
        try {
            session = HibernateUtil.getSession();
            tx = session.beginTransaction();
            User user = new User();
            user.setName( "xigua" );
            user.setBirthday( new Date());
            session.save(user);

            user = new User();
            user.setName( "donggua" );
            user.setBirthday( new Date());
            session.save(user);
            tx.commit();
        } catch (Exception e) {
            if (tx != null ) {
                tx.rollback();
            }
        } finally {
            if (session != null ) {
                session.close();
            }
        }
    }

    public static User namedSqlQuery(String name) {
        Session session = null ;
        try {
            session = HibernateUtil.getSession();
            Query query = session.getNamedQuery( "getUserByName" );
            query.setParameter( "name" , name);
            Object[] obj = (Object[]) query.uniqueResult();
            if (obj != null ) {
                User user = new User();
                user.setId(Long.valueOf(obj[ 0 ].toString()));
                user.setName(obj[ 1 ].toString());
                return user;
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (session != null ) {
                session.close();
            }
        }

        return null ;
    }

}

映射文件中还有些其它的配置，暂时还没具体搞懂，比如下面红色的代码：

<sql-query name= "getUserByName" >
        <![CDATA[select id, name from user where name = :name]]>
        <query-param name= "name" type= "string" />
        < return ></ return >
        < return -join alias= "" property= "" ></ return -join>
        < return -scalar column= "" />
        <synchronize table= "" />
    </sql-query>

还有一点像说明的是<query>跟<sql-query>的配置是可以放到<class>节点里面的。

我现在是放在<class>节点外面，表示全局可用，这里需要注意不要跟其它映射文件中定义的<query>或<sql-query>同名。

如果将<query>或<sql-query>放在<class>节点里面，在java代码中使用的时候需要将package名跟class名都写上，具体见下面配置的映射文件代码跟测试代码。

映射文件代码：

<? xml version = "1.0" ?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "D:\tools\hibernate\dtd\hibernate-mapping-3.0.dtd">
< hibernate-mapping
    package = "com.xigua.domain" >
    < class name = "User" >
        < id name = "id" >
            < generator class = "native" />
        </ id >
        < property name = "name" />
        < property name = "birthday" />

        <!-- 定义一个查询，名称为getUserByName (这里将<query>放到<class>节点里面来)-->
        < query name = "getUserByName" >
            <![CDATA[from User where name = :name]]>
        </ query >

    </ class >



</ hibernate-mapping >

 java测试代码

package com.xigua.test;

import java.util.Date;
import java.util.List;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.xigua.domain.User;
import com.xigua.utils.HibernateUtil;

public class Test9 {

    public static void main(String[] args) {
        addUser();
        String name = "xigua" ;
        List<User> list = namedQuery(name);
        if (list != null && !list.isEmpty()) {
            for (User user : list) {
                System.out.println(user.getId() + ", " + user.getName() + ", " + user.getBirthday());
            }
        }
    }

    public static void addUser() {
        Session session = null ;
        Transaction tx = null ;
        try {
            session = HibernateUtil.getSession();
            tx = session.beginTransaction();
            User user = new User();
            user.setName( "xigua" );
            user.setBirthday( new Date());
            session.save(user);

            user = new User();
            user.setName( "donggua" );
            user.setBirthday( new Date());
            session.save(user);
            tx.commit();
        } catch (Exception e) {
            if (tx != null ) {
                tx.rollback();
            }
        } finally {
            if (session != null ) {
                session.close();
            }
        }
    }

    public static List<User> namedQuery(String name) {
        Session session = null ;
        try {
            session = HibernateUtil.getSession();
            Query query = session.getNamedQuery( "com.xigua.domain.User.getUserByName" );
            query.setParameter( "name" , name);
            return query.list();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (session != null ) {
                session.close();
            }
        }

        return null ;
    }

}

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