hibernate框架学习之数据抓取(加载)策略helloworld

2021-09-22 08:01:11

package cn.itcast.h3.query.hql;

import java.util.List;

import org.hibernate.Query;

import org.hibernate.Session;

import cn.itcast.h3.query.hql.vo.TeacherModel;

import cn.itcast.util.HibernateUtil;

public class MainRelaApp {

    //fetch="select" lazy="false"

    void selectFalse(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from TeacherModel");

        List<TeacherModel> queryList  = q.list();

        System.out.println(queryList.get(0).getStudents().size());

        System.out.println(queryList.get(0).getStudents());

        s.close();

    }

    //fetch="select" lazy="true"

    void selectTrue(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from TeacherModel");

        List<TeacherModel> queryList  = q.list();

        System.out.println(queryList.get(0).getStudents());

        System.out.println(queryList.get(0).getStudents().size());

        s.close();

    }

    //fetch="select" lazy="extra"

    void selectExtra(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from TeacherModel");

        List<TeacherModel> queryList  = q.list();

        System.out.println(queryList.get(0).getStudents());

        System.out.println(queryList.get(0).getStudents().size());

        s.close();

    }

    //fetch="subselect" lazy="false"

    void subselectFlase(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from TeacherModel");

        List<TeacherModel> queryList  = q.list();

        System.out.println(queryList.get(0).getStudents());

        System.out.println(queryList.get(0).getStudents().size());

        s.close();

    }

    //fetch="subselect" lazy="true"

    void subselectTrue(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from TeacherModel");

        List<TeacherModel> queryList  = q.list();

//        System.out.println(queryList.get(0).getStudents().size());

        System.out.println(queryList.get(0).getStudents());

        s.close();

    }

    //fetch="subselect" lazy="extra"

    void subselectExtra(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from TeacherModel");

        List<TeacherModel> queryList  = q.list();

        System.out.println(queryList.get(0).getStudents().size());

        System.out.println(queryList.get(0).getStudents());

        s.close();

    }

    //fetch="subselect" lazy="extra"  Query-》OID  load get

    void subselectExtra2(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from TeacherModel where uuid = 1");

        List<TeacherModel> queryList  = q.list();

        System.out.println(queryList.get(0).getStudents().size());

        System.out.println(queryList.get(0).getStudents());

        s.close();

    }

    //fetch="join" lazy="false"

    void joinFalse(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from TeacherModel");

        List<TeacherModel> queryList  = q.list();

        System.out.println(queryList.get(0).getStudents().size());

        System.out.println(queryList.get(0).getStudents());

        s.close();

    }

    //fetch="join" lazy="true"

    void joinTrue(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from TeacherModel");

        List<TeacherModel> queryList  = q.list();

        System.out.println(queryList.get(0).getStudents().size());

        System.out.println(queryList.get(0).getStudents());

        s.close();

    }

    //fetch="join" lazy="extra"

    void joinExtra(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from TeacherModel");

        List<TeacherModel> queryList  = q.list();

        System.out.println(queryList.get(0).getStudents().size());

        System.out.println(queryList.get(0).getStudents());

        s.close();

    }

    //fetch="join" lazy="extra" get  OID

    void joinExtra2(){

        Session s = HibernateUtil.getSession();

        TeacherModel tm = (TeacherModel) s.get(TeacherModel.class, 2L);

        System.out.println(tm.getStudents().size());

        System.out.println(tm.getStudents());

        s.close();

    }

    //批量抓取策略

    void batchQuery(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from TeacherModel");

        List<TeacherModel> queryList  = q.list();

//        System.out.println(queryList.get(0).getStudents().size());

//        System.out.println(queryList.get(0).getStudents());

        s.close();

    }

    public static void main(String[] args) {

        new MainRelaApp().batchQuery();

    }

}

package cn.itcast.h3.query.hql;

import java.util.List;

import org.hibernate.Query;

import org.hibernate.Session;

import cn.itcast.h3.query.hql.vo.StudentModel;

import cn.itcast.util.HibernateUtil;

//从关联数据检索策略

public class SubRelaApp {

    //fetch="select" lazy="false"

    void selectFlase(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from StudentModel");

        List<StudentModel> queryList  = q.list();

        System.out.println(queryList.get(0).getTeacher());

        s.close();

    }

    //fetch="select" lazy="proxy"

    void selectProxy(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from StudentModel");

        List<StudentModel> queryList  = q.list();

//        System.out.println(queryList.get(0).getTeacher());

//        System.out.println(queryList.get(11).getTeacher());

//        System.out.println(queryList.get(21).getTeacher());

        s.close();

    }

    //fetch="join" lazy="false"

    void joinFalse(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from StudentModel");

        List<StudentModel> queryList  = q.list();

        System.out.println(queryList.get(0).getTeacher());

        System.out.println(queryList.get(11).getTeacher());

        System.out.println(queryList.get(21).getTeacher());

        s.close();

    }

    //fetch="join" lazy="proxy"

    void joinProxy(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from StudentModel");

        List<StudentModel> queryList  = q.list();

        System.out.println(queryList.get(0).getTeacher());

        System.out.println(queryList.get(11).getTeacher());

        System.out.println(queryList.get(21).getTeacher());

        s.close();

    }

    //fetch="join" lazy="proxy" 使用OID查询

    void joinProxy2(){

        Session s = HibernateUtil.getSession();

        StudentModel sm = (StudentModel) s.get(StudentModel.class, 4L);

        System.out.println(sm.getTeacher());

        s.close();

    }

    //批量加载

    void batchQuery(){

        Session s = HibernateUtil.getSession();

        Query q = s.createQuery("from StudentModel");

        List<StudentModel> queryList  = q.list();

//        System.out.println(queryList.get(0).getTeacher());

//        System.out.println(queryList.get(11).getTeacher());

//        System.out.println(queryList.get(21).getTeacher());

        s.close();

    }

    public static void main(String[] args) {

        new SubRelaApp().batchQuery();

    }

}

TeacherModel.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE hibernate-mapping PUBLIC

        '-//Hibernate/Hibernate Mapping DTD 3.0//EN'

        'http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd'>

<hibernate-mapping>

    <class name="cn.itcast.h3.query.hql.vo.TeacherModel" table="tbl_teacher" lazy="false">

        <id name="uuid" column="uuid">

            <generator class="native" />

        </id>

        <property name="teacherName"/>

        <property name="nick"/>

        <set
fetch="select"

            lazy="false"

            batch-size="5"

            name="students"

            >

            <key column="teacherUuid"/>

            <one-to-many class="cn.itcast.h3.query.hql.vo.StudentModel"/>

        </set>

    </class>

</hibernate-mapping>

码农公寓

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