11.hibernate的连接查询

1.创建如下javaweb项目结构

2.在项目的src下创建hibernate.cfg.xml主配置文件

 <?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>
   <session-factory>
     <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
     <property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:orcl</property>
     <property name="connection.username">scott</property>
     <property name="connection.password">tiger</property>
     <property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>
     <property name="show_sql">true</property>
     <property name="format_sql">true</property>
     <mapping resource="com/entity/Dept.hbm.xml"/>
     <mapping resource="com/entity/Emp.hbm.xml"/>
   </session-factory>
 </hibernate-configuration>

hibernate.cfg.xml

3.在项目的src下的com.util包下创建HibernateUtil.java

 package com.util;

 import org.hibernate.HibernateException;
 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.cfg.Configuration;

 public class HibernateUtil {
     private static ThreadLocal<Session> thread=new ThreadLocal<Session>();
     private static Configuration config=null;
     private static SessionFactory factory=null;
     /**
      * 读取配置文件
      */
     static{
         try {
             config=new Configuration().configure("/hibernate.cfg.xml");
             factory=config.buildSessionFactory();
         } catch (HibernateException e) {
             System.out.println("读取配置文件失败或创建factory失败");
             e.printStackTrace();
         }
     }
     /**
      * 打开session
      * @return
      */
     public static Session getSession(){
         Session session =thread.get();
         if(session==null){
             session=factory.openSession();
             thread.set(session);
         }
         return session;
     }
     /**
      * 关闭session
      */
     public static void closeSession(){
         Session session =thread.get();
         thread.set(null);
         session.close();

     }

 }

HibernateUtil.java

4.在项目的src下的com.entity包下创建Dept.java

 package com.entity;

 import java.util.HashSet;
 import java.util.Set;

 public class Dept {
     private Integer deptno;
     private String dname;
     private String loc;
     private Set<Emp> emps =new HashSet<Emp>();

     public Dept() {
     }

     public Dept(Integer deptno, String dname, String loc) {
         this.deptno = deptno;
         this.dname = dname;
         this.loc = loc;
     }

     public Dept(Integer deptno, String dname, String loc, Set<Emp> emps) {
         this.deptno = deptno;
         this.dname = dname;
         this.loc = loc;
         this.emps = emps;
     }
     public Integer getDeptno() {
         return deptno;
     }
     public void setDeptno(Integer deptno) {
         this.deptno = deptno;
     }
     public String getDname() {
         return dname;
     }
     public void setDname(String dname) {
         this.dname = dname;
     }
     public String getLoc() {
         return loc;
     }
     public void setLoc(String loc) {
         this.loc = loc;
     }
     public Set<Emp> getEmps() {
         return emps;
     }
     public void setEmps(Set<Emp> emps) {
         this.emps = emps;
     }

     @Override
     public String toString() {
         return "Dept [deptno=" + deptno + ", dname=" + dname + ", loc=" + loc + "]";
     }

 }

Dept.java

5.在项目的src下的com.entity包下创建Emp.java

 package com.entity;

 public class Emp {
     private Integer empno;
     private String ename;
     private String job;
     private Integer sal;
     private Dept dept;

     public Emp() {
     }

     public Emp(Integer empno, String ename, String job, Integer sal) {
         super();
         this.empno = empno;
         this.ename = ename;
         this.job = job;
         this.sal = sal;
     }

     public Emp(Integer empno, String ename, String job, Integer sal, Dept dept) {
         super();
         this.empno = empno;
         this.ename = ename;
         this.job = job;
         this.sal = sal;
         this.dept = dept;
     }

     public Integer getEmpno() {
         return empno;
     }

     public void setEmpno(Integer empno) {
         this.empno = empno;
     }

     public String getEname() {
         return ename;
     }

     public void setEname(String ename) {
         this.ename = ename;
     }

     public String getJob() {
         return job;
     }

     public void setJob(String job) {
         this.job = job;
     }

     public Integer getSal() {
         return sal;
     }

     public void setSal(Integer sal) {
         this.sal = sal;
     }

     public Dept getDept() {
         return dept;
     }

     public void setDept(Dept dept) {
         this.dept = dept;
     }

     @Override
     public String toString() {
         return "Emp [ empno=" + empno + ", ename=" + ename
                 + ", job=" + job + ", sal=" + sal + "]";
     }

 }

Emp.java

6.在项目的src下的com.entity包下创建Dept.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="com.entity.Dept" table="DEPT">
      <id name="deptno" type="java.lang.Integer" column="DEPTNO">
        <generator class="assigned"/>
      </id>
      <property name="dname" type="java.lang.String" column="DNAME"/>
      <property name="loc" type="java.lang.String" column="LOC"/>
      <!-- 一对多 -->
      <set name="emps" inverse="true" cascade="save-update">
         <key column="DEPTNO"></key>
         <one-to-many class="com.entity.Emp"/>
      </set>
    </class>
 </hibernate-mapping>

Dept.hbm.xml

7.在项目的src下的com.entity包下创建Emp.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="com.entity.Emp" table="EMP">
      <id name="empno" type="java.lang.Integer" column="EMPNO">
        <generator class="assigned"/>
      </id>
      <property name="ename" type="java.lang.String" column="ENAME"/>
      <property name="job" type="java.lang.String" column="JOB"/>
      <property name="sal" type="java.lang.Integer" column="SAL"/>
      <!-- 多对一 -->
      <many-to-one name="dept" class="com.entity.Dept" column="DEPTNO"/>
   </class>
 </hibernate-mapping>

Emp.hbm.xml

8.在项目的src下的com.dao包下创建DpetDao.java

 package com.dao;

 import java.util.List;

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

 import com.entity.Dept;
 import com.util.HibernateUtil;

 public class DpetDao {

     public static void main(String[] args) {
         System.out.println("-----------1.关联查询-----------");
         //getDept();
         System.out.println("-------2.内连接-------");
         innerJoin();
         System.out.println("-------3.迫切内连接-------");
         innerJoinFetch();
         System.out.println("-------4.左连接-------");
         leftJoin();
         System.out.println("-------5.迫切左连接-------");
         leftJoinFetch();
         System.out.println("-------6.右连接-------");
         rightJoin();

     }
     /**
      * 6.右连接
      */
     private static void rightJoin() {
         Session session=HibernateUtil.getSession();
         String hql="from Dept d right join d.emps ";
         Query query=session.createQuery(hql);
         /*list集合中的每个元素都是一个Object数组,数组的第一个元素时Dept对象,
          * 第二个元素时Emp对象,Dept对象的emps集合元素没有被初始化,
          * 即emps集合没有存放关联的Emp对象*/
         List<Object[]> list=query.list();
         System.out.println("dept对象"+"~~"+"emp对象");
         for (Object[] obj : list) {
             System.out.println(obj[0]);
             System.out.println(obj[1]);
         }
         HibernateUtil.closeSession();

     }
     /**
      * 5.迫切左连接
      */
     private static void leftJoinFetch() {
         Session session=HibernateUtil.getSession();
         /*Hibernate使用fetch关键字实现了将Emp对象读取出来后立即填充到对应的Dept对象
          * 的集合属性中,*/
         String hql="select distinct d from Dept d left join fetch d.emps ";
         Query query=session.createQuery(hql);
         List<Dept> list=query.list();
         for (Dept dept : list) {
             System.out.println(dept);
         }
         HibernateUtil.closeSession();
     }
     /**
      * 4.左连接
      */
     private static void leftJoin() {
         Session session=HibernateUtil.getSession();
         String hql="from Dept d left join d.emps ";
         Query query=session.createQuery(hql);
         /*list集合中的每个元素都是一个Object数组,数组的第一个元素时Dept对象,
          * 第二个元素时Emp对象,Dept对象的emps集合元素没有被初始化,
          * 即emps集合没有存放关联的Emp对象*/
         List<Object[]> list=query.list();
         System.out.println("dept对象"+"~~"+"emp对象");
         for (Object[] obj : list) {
             System.out.println(obj[0]);
             System.out.println(obj[1]);
         }
         HibernateUtil.closeSession();
     }
     /**
      * 3.迫切内连接
      */
     private static void innerJoinFetch() {
         Session session=HibernateUtil.getSession();
         /*Hibernate使用fetch关键字实现了将Emp对象读取出来后立即填充到对应的Dept对象
          * 的集合属性中,*/
         String hql="select distinct d from Dept d inner join fetch d.emps ";
         Query query=session.createQuery(hql);
         List<Dept> list=query.list();
         for (Dept dept : list) {
             System.out.println(dept);
         }
         HibernateUtil.closeSession();
     }
     /**
      * 2.内连接
      */
     private static void innerJoin() {
         Session session=HibernateUtil.getSession();
         String hql="from Dept d inner join d.emps ";
         Query query=session.createQuery(hql);
         /*list集合中的每个元素都是一个Object数组,数组的第一个元素时Dept对象,
          * 第二个元素时Emp对象,Dept对象的emps集合元素没有被初始化,
          * 即emps集合没有存放关联的Emp对象*/
         List<Object[]> list=query.list();
         System.out.println("dept对象"+"~~"+"emp对象");
         for (Object[] obj : list) {
             System.out.println(obj[0]);
             System.out.println(obj[1]);
         }
         HibernateUtil.closeSession();
     }
     /**
      * Exception in thread "main" java.lang.StackOverflowError
      * 内存溢出:死循环
      * hiberante双向关联时:打印内容时不能你中有我,我中有你,查询默认是懒加载
      *
      */
     private static void getDept() {
         Session session=HibernateUtil.getSession();
         String hql="from Dept";
         Query query=session.createQuery(hql);
         List<Dept> list=query.list();
         for (Dept dept : list) {
             System.out.println(dept);
             System.out.println(dept.getEmps());
         }
         HibernateUtil.closeSession();

     }

 }

DpetDao.java

9.运行结果如下：remdeme.txt

 1.内连接
 Hibernate:
     select
         dept0_.DEPTNO as DEPTNO0_0_,
         emps1_.EMPNO as EMPNO1_1_,
         dept0_.DNAME as DNAME0_0_,
         dept0_.LOC as LOC0_0_,
         emps1_.ENAME as ENAME1_1_,
         emps1_.JOB as JOB1_1_,
         emps1_.SAL as SAL1_1_,
         emps1_.DEPTNO as DEPTNO1_1_
     from
         DEPT dept0_
     inner join
         EMP emps1_
             on dept0_.DEPTNO=emps1_.DEPTNO
 2.迫切内连接
  select
         dept0_.DEPTNO as DEPTNO0_0_,
         emps1_.EMPNO as EMPNO1_1_,
         dept0_.DNAME as DNAME0_0_,
         dept0_.LOC as LOC0_0_,
         emps1_.ENAME as ENAME1_1_,
         emps1_.JOB as JOB1_1_,
         emps1_.SAL as SAL1_1_,
         emps1_.DEPTNO as DEPTNO1_1_,
         emps1_.DEPTNO as DEPTNO0__,
         emps1_.EMPNO as EMPNO0__
     from
         DEPT dept0_
     inner join
         EMP emps1_
             on dept0_.DEPTNO=emps1_.DEPTNO
  -------4.左连接-------
 Hibernate:
     select
         dept0_.DEPTNO as DEPTNO0_0_,
         emps1_.EMPNO as EMPNO1_1_,
         dept0_.DNAME as DNAME0_0_,
         dept0_.LOC as LOC0_0_,
         emps1_.ENAME as ENAME1_1_,
         emps1_.JOB as JOB1_1_,
         emps1_.SAL as SAL1_1_,
         emps1_.DEPTNO as DEPTNO1_1_
     from
         DEPT dept0_
     left outer join
         EMP emps1_
             on dept0_.DEPTNO=emps1_.DEPTNO  

  -------5.迫切左连接-------
 Hibernate:
     select
         distinct dept0_.DEPTNO as DEPTNO0_0_,
         emps1_.EMPNO as EMPNO1_1_,
         dept0_.DNAME as DNAME0_0_,
         dept0_.LOC as LOC0_0_,
         emps1_.ENAME as ENAME1_1_,
         emps1_.JOB as JOB1_1_,
         emps1_.SAL as SAL1_1_,
         emps1_.DEPTNO as DEPTNO1_1_,
         emps1_.DEPTNO as DEPTNO0__,
         emps1_.EMPNO as EMPNO0__
     from
         DEPT dept0_
     left outer join
         EMP emps1_
             on dept0_.DEPTNO=emps1_.DEPTNO
  -------6.右连接-------
 Hibernate:
     select
         dept0_.DEPTNO as DEPTNO0_0_,
         emps1_.EMPNO as EMPNO1_1_,
         dept0_.DNAME as DNAME0_0_,
         dept0_.LOC as LOC0_0_,
         emps1_.ENAME as ENAME1_1_,
         emps1_.JOB as JOB1_1_,
         emps1_.SAL as SAL1_1_,
         emps1_.DEPTNO as DEPTNO1_1_
     from
         DEPT dept0_
     right outer join
         EMP emps1_
             on dept0_.DEPTNO=emps1_.DEPTNO