hql查询语句 内存中的情况，fetch迫切查询关键字

Classes.java

 package cn.itcast.hiberate.sh.domain;

 import java.io.Serializable;
 import java.util.Set;

 public class Classes implements Serializable{
     private Long cid;
     private String cname;
     private String description;

     public Classes(){}

     public Classes(String cname,String description){
         this.cname = cname;
         this.description = description;
     }

     public Long getCid() {
         return cid;
     }

     public void setCid(Long cid) {
         this.cid = cid;
     }

     public String getCname() {
         return cname;
     }

     public void setCname(String cname) {
         this.cname = cname;
     }

     public String getDescription() {
         return description;
     }

     public void setDescription(String description) {
         this.description = description;
     }

     public Set<Student> getStudents() {
         return students;
     }

     public void setStudents(Set<Student> students) {
         this.students = students;
     }

     private Set students;
 }

 <?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="cn.itcast.hiberate.sh.domain.Classes">
         <id name="cid" length="5" type="java.lang.Long">
             <generator class="increment"></generator>
         </id>
         <property name="cname" length="20" type="java.lang.String"></property>

         <property name="description" length="100" type="java.lang.String"></property>
         <!--
             set元素对应类中的set集合
             通过set元素使classes表与student表建立关联
                key是通过外键的形式让两张表建立关联
                one-to-many是通过类的形式让两个类建立关联

             cascade 级联
                save-update
                    1、当 保存班级的时候，对学生进行怎么样的操作
                         如果学生对象在数据库中没有对应的值，这个时候会执行save操作
                         如果学生对象在数据库中有对应的值，这个时候会执行update操作
                delete
                all
             inverse  维护关系
                true      不维护关系
                false     维护关系
                default   false
          -->
         <set name="students" cascade="save-update" inverse="true" lazy="false" fetch="join">
             <!--
                 key是用来描述外键
              -->
             <key>
                 <column name="cid"></column>
             </key>
             <one-to-many class="cn.itcast.hiberate.sh.domain.Student"/>
         </set>
     </class>
 </hibernate-mapping>

Course.java

 package cn.itcast.hiberate.sh.domain;

 import java.io.Serializable;
 import java.util.Set;

 public class Course implements Serializable{
     private Long cid;
     private String cname;
     private String description;

     public Long getCid() {
         return cid;
     }

     public void setCid(Long cid) {
         this.cid = cid;
     }

     public String getCname() {
         return cname;
     }

     public void setCname(String cname) {
         this.cname = cname;
     }

     public String getDescription() {
         return description;
     }

     public void setDescription(String description) {
         this.description = description;
     }

     public Set<Student> getStudents() {
         return students;
     }

     public void setStudents(Set<Student> students) {
         this.students = students;
     }

     private Set<Student> students;
 }

 <?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">
 <!--
     建立表和类的对应关系
  -->
 <hibernate-mapping>
     <class name="cn.itcast.hiberate.sh.domain.Course">
         <id name="cid" type="java.lang.Long" length="5">
             <generator class="increment"></generator>
         </id>
         <property name="cname" type="java.lang.String" length="20"></property>
         <property name="description" type="java.lang.String" length="50"></property>
         <!--
             table
                student与course在数据库的层次上通过该表实现关联
          -->
         <set name="students" table="student_course">
             <key>
             <!--
                 在哪个映射文件中，就添加哪个
              -->
                 <column name="cid"></column>
             </key>
             <!--
                 column表示外键
              -->
             <many-to-many class="cn.itcast.hiberate.sh.domain.Student" column="sid"></many-to-many>
         </set>
     </class>
 </hibernate-mapping>

Student.java

 package cn.itcast.hiberate.sh.domain;

 import java.io.Serializable;
 import java.util.HashSet;
 import java.util.Set;

 public class Student implements Serializable{
     private Long sid;
     private String sname;

     private Classes classes;

     private Set<Course> courses = new HashSet<Course>(0);

     public Set<Course> getCourses() {
         return courses;
     }
     public void setCourses(Set<Course> courses) {
         this.courses = courses;
     }
     public Classes getClasses() {
         return classes;
     }
     public void setClasses(Classes classes) {
         this.classes = classes;
     }
     public Long getSid() {
         return sid;
     }
     public void setSid(Long sid) {
         this.sid = sid;
     }
     public String getSname() {
         return sname;
     }
     public void setSname(String sname) {
         this.sname = sname;
     }
     public String getDescription() {
         return description;
     }
     public void setDescription(String description) {
         this.description = description;
     }
     private String description;
 }

 <?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="cn.itcast.hiberate.sh.domain.Classes">
         <id name="cid" length="5" type="java.lang.Long">
             <generator class="increment"></generator>
         </id>
         <property name="cname" length="20" type="java.lang.String"></property>

         <property name="description" length="100" type="java.lang.String"></property>
         <!--
             set元素对应类中的set集合
             通过set元素使classes表与student表建立关联
                key是通过外键的形式让两张表建立关联
                one-to-many是通过类的形式让两个类建立关联

             cascade 级联
                save-update
                    1、当 保存班级的时候，对学生进行怎么样的操作
                         如果学生对象在数据库中没有对应的值，这个时候会执行save操作
                         如果学生对象在数据库中有对应的值，这个时候会执行update操作
                delete
                all
             inverse  维护关系
                true      不维护关系
                false     维护关系
                default   false
          -->
         <set name="students" cascade="save-update" inverse="true" lazy="false" fetch="join">
             <!--
                 key是用来描述外键
              -->
             <key>
                 <column name="cid"></column>
             </key>
             <one-to-many class="cn.itcast.hiberate.sh.domain.Student"/>
         </set>
     </class>
 </hibernate-mapping>

Hibernate.cfg.xml

 <?xml version='1.0' encoding='utf-8'?>
 <!DOCTYPE hibernate-configuration PUBLIC
         "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
         "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
 <hibernate-configuration>
     <!--
         一个session-factory只能连接一个数据库
     -->
 <session-factory>
     <!--
         数据库的用户名
     -->
     <property name="connection.username">root</property>

     <property name="connection.driver_class">
         com.mysql.jdbc.Driver
     </property>

     <!--
         密码
     -->
     <property name="connection.password">friends</property>
     <!--
         url
     -->
     <property name="connection.url">
         jdbc:mysql://localhost:3306/mydatabase
     </property>
     <!--
         作用：根据持久化类和映射文件生成表
         validate
         create-drop
         create
         update
     -->
     <property name="hbm2ddl.auto">update</property>

     <property name="hibernate.dialect">
         org.hibernate.dialect.MySQLInnoDBDialect
     </property>
     <!--
         显示hibernate内部生成的sql语句
     -->
     <property name="show_sql">true</property>
     <property name="format_sql">true</property>
     <mapping resource="cn/itcast/hiberate/sh/domain/Classes.hbm.xml" />
     <mapping resource="cn/itcast/hiberate/sh/domain/Student.hbm.xml" />
      <mapping resource="cn/itcast/hiberate/sh/domain/Course.hbm.xml" /> 

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

 package cn.itcast.hibernate.sh.dao;

 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;

 import org.hibernate.Query;
 import org.hibernate.Session;
 import org.junit.Test;

 import cn.itcast.hiberate.sh.domain.Classes;
 import cn.itcast.hiberate.sh.domain.Course;
 import cn.itcast.hiberate.sh.domain.Student;
 import cn.itcast.hibernate.sh.utils.HiberanteUtils;

 /**
  * 单表
  *
  * 一对多和多对多
  *
  * 多表的结合
  * @author Think
  *
  */
 public class HQLDao extends HiberanteUtils{
     public List<Classes> queryAllClasses(){
         Session session = sessionFactory.openSession();
         List<Classes> cList = session.createQuery("from Classes").list();
         session.close();
         return cList;
     }

     public List queryClasses_Properties(){
         Session session = sessionFactory.openSession();
         List cList = session.createQuery("select cid,cname from Classes").list();
         session.close();
         return cList;
     }

     public List<Classes> queryClasses_Constructor(){
         Session session = sessionFactory.openSession();
         List<Classes> cList = session.createQuery("select new cn.itcast.hiberate.sh.domain.Classes(cname,description) from Classes").list();
         session.close();
         return cList;
     }

     public Classes queryClasses_Condition(){
         Session session = sessionFactory.openSession();
         Query query = session.createQuery("select new cn.itcast.hiberate.sh.domain.Classes(cname,description) from Classes where cid=:cid");
         query.setLong("cid", 1L);
         Classes classes = (Classes)query.uniqueResult();
         System.out.println(classes.getCname());
         session.close();
         return classes;
     }

     public Classes queryClasses_Condition_2(){
         Session session = sessionFactory.openSession();
         Query query = session.createQuery("select new cn.itcast.hiberate.sh.domain.Classes(cname,description) from Classes where cid=?");
         query.setLong(0, 1L);
         Classes classes = (Classes)query.uniqueResult();
         System.out.println(classes.getCname());
         session.close();
         return classes;
     }

     /**
      * order by,group by,sun,min,max,avg,having等都适用
      * @return
      */

     /**
      * 子查询
      */
     public void queryClasses_SubSelect(){
         Session session = sessionFactory.openSession();
         List<Classes> cList = session.createQuery("from Classes where cid in(select cid from Classes where cid in(1,2,3))").list();
         session.close();
     }

     public static HQLDao getInstance(){
         return new HQLDao();
     }

     /*********************************************************************************************/
        /**
         * 一对多
         *    等值连接          查询出来的机构很差
         *    内连接
         *    左外连接
         *    迫切左外连接
         */
     public List<Classes> queryClasses_Student_EQ(){
         Session session = sessionFactory.openSession();
         List<Classes> cList = session.createQuery("from Classes c,Student s where c.cid=s.classes.cid").list();
         session.close();
         return cList;
     }

     /**
      * 内连接
      * @return
      */
     public List<Classes> queryClasses_Student_INNER(){
         Session session = sessionFactory.openSession();
         List<Classes> cList = session.createQuery("from Classes c inner join c.students").list();
         session.close();
         return cList;
     }

     /**
      * 迫切内连接
      * @return
      */
     public List<Classes> queryClasses_Student_INNER_FETCH(){
         Session session = sessionFactory.openSession();
         List<Classes> cList = session.createQuery("from Classes c inner join fetch c.students").list();
         session.close();
         return cList;
     }

     /**
      * 左外连接
      */
     public List<Classes> queryClasses_Student_LeftJoin(){
         Session session = sessionFactory.openSession();
         List<Classes> cList = session.createQuery("from Classes c left outer join c.students").list();
         session.close();
         return cList;
     }

     /**
      * 迫切左外连接
      */
     public List<Classes> queryClasses_Student_LeftJoin_fetch(){
         Session session = sessionFactory.openSession();
         String hql = "from Classes c left outer join fetch c.students";
         hql = "from Student s left outer join fetch s.classes c";
         List<Classes> cList = session.createQuery(hql).list();
         session.close();
         return cList;
     }

     /**
      * 带select的查询
      */
     public List<Classes> queryClasses_Student_Select(){
         Session session = sessionFactory.openSession();
         String hql = "select new cn.itcast.hiberate.sh.domain.ClassesView(c.cname,s.sname) " +
                      "from Student s left outer join s.classes c";
         List<Classes> cList = session.createQuery(hql).list();
         session.close();
         return cList;
     }

     /**
      * 多对多
      */
     public void testQueryCourse_Student(){
         Session session = sessionFactory.openSession();
         List<Student> studentList = session.createQuery("from Student s inner join fetch s.courses c").list();
         session.close();
     }

     /**
      * 一对多结合多对多
      */
     public List<Student> queryClasses_Student_Course(){
         Session session = sessionFactory.openSession();
         String hql = "from Classes cs inner join fetch cs.students s inner join fetch s.courses c";
         hql = "from Student s inner join fetch s.classes cs inner join fetch s.courses c";
         //hql = "from Classes cs left outer join fetch cs.students s left outer join fetch s.courses c";
         List<Student> cList = session.createQuery(hql).list();
 //        Set<Classes> cset = new HashSet<Classes>(cList);
 //        cList = new ArrayList<Classes>(cset);
         System.out.println(cList.size());
 //        for(Classes classes:cList){
 //            System.out.println(classes.getCid());
 //            Set<Student> students = classes.getStudents();
 //            for(Student student:students){
 //                System.out.println(student.getSname());
 //                Set<Course> courses = student.getCourses();
 //                for(Course course:courses){
 //                    System.out.println(course.getCname());
 //                }
 //            }
 //        }
         session.close();
         return cList;
     }
 }