[SXT][WY]Hibernate13 树形结构作业及HQL

树结构

 

public class Node {

 // 标识符
 private int id;

 // 节点名称
 private String name;

 // 层次
 private int level;

 // 是否叶子节点
 private boolean leaf;

 // 父节点 * --- 1
 private Node parent;

 // 子节点 1 --- *
 private Set children;

 

}

 

<?xml version="1.0"?>
<!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.bjsxt.hibernate.Node" table="t_node">
        <id name="id">
            <generator class="native"/>
        </id>
        <property name="name"/>
        <property name="level"/>
        <property name="leaf"/>
        <many-to-one name="parent" column="pid"/>
        <set name="children" lazy="extra" inverse="true">
         <key column="pid"/>
         <one-to-many class="com.bjsxt.hibernate.Node"/>
        </set>
    </class>
</hibernate-mapping>

 

HQL

 

hibernate查询语言hql

在hql中关键字不区分大小写，但是属性和类名区分大小写

1、简单属性查询【重要】
 * 单一属性查询，返回结果集属性列表，元素类型和实体类中相应的属性类型一致
 * 多个属性查询,返回的集合元素是对象数组,数组元素的类型和对应的属性在实体类中的类型一致
   数组的长度取决与select中属性的个数
 * 如果认为返回数组不够对象化，可以采用hql动态实例化Student对象
 参见：SimplePropertyQueryTest.java 

2、实体对象查询【重要】
 * N + 1问题，在默认情况下，使用query.iterate查询，有可以能出现N+1问题
   所谓的N+1是在查询的时候发出了N+1条sql语句
   1: 首先发出一条查询对象id列表的sql
   N: 根据id列表到缓存中查询，如果缓存中不存在与之匹配的数据，那么会根据id发出相应的sql语句
 * list和iterate的区别？
  * list每次都会发出sql语句，list会向缓存中放入数据，而不利用缓存中的数据
  * iterate：在默认情况下iterate利用缓存数据，但如果缓存中不存在数据有可以能出现N+1问题
 参见：SimpleObjectQueryTest1.java/SimpleObjectQueryTest2.java
 
3、条件查询【重要】 
 * 可以采用拼字符串的方式传递参数
 * 可以采用 ？来传递参数（索引从0开始）
 * 可以采用 :参数名 来传递参数
 * 如果传递多个参数，可以采用setParamterList方法
 * 在hql中可以使用数据库的函数，如：date_format
 参见：SimpleConditionQueryTest.java  
   
4、hibernate也支持直接使用sql进行查询
 参见：SqlQueryTest.java

5、外置命名查询
 * 在映射文件中采用<query>标签来定义hql
 * 在程序中采用session.getNamedQuery()方法得到hql查询串
 参见：Student.hbm.xml、NameQueryTest.java
 
6、查询过滤器 
 * 在映射文件中定义过滤器参数
 * 在类的映射中使用这些参数
 * 在程序中启用过滤器
 参见：Student.hbm.xml、FilterQueryTest.java
 
7、分页查询【重要】 
 * setFirstResult()，从0开始
 * setMaxResults,每页显示多少条数据
 参见：PageQueryTest.java
    
8、对象导航查询，在hql中采用 . 进行导航【重要】
 参见：ObjectNavQueryTest.java
 
9、连接查询【重要】
 * 内连
 * 外连接（左连接/右连接） 
 参见：JoinQueryTest.java
 
10、统计查询【重要】
 参见：StatQueryTest.java
 
11、DML风格的操作（尽量少用，因为和缓存不同步）
 参见：DMLQueryTest.java

 

 

 

1、简单属性查询【重要】

 /**
  * 单一属性查询
  */
 public void testQuery1() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //返回结果集属性列表，元素类型和实体类中相应的属性类型一致
   List students = session.createQuery("select name from Student").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    String name = (String)iter.next();
    System.out.println(name);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }

 

/**
  * 多个属性查询
  */
 public void testQuery2() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //查询多个属性，其集合元素是对象数组
   //数组元素的类型和对应的属性在实体类中的类型一致
   //数组的长度取决与select中属性的个数
   List students = session.createQuery("select id, name from Student").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }

 

/**
  * 返回Student实体对象,  注意 要写相应的构造函数！！
  */
 public void testQuery3() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //如果认为返回数组不够对象化，可以采用hql动态实例化Student对象
   //此时list中为Student对象集合
   List students = session.createQuery("select new Student(id, name) from Student").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Student student = (Student)iter.next();
    System.out.println(student.getId() + "," + student.getName());
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }

 

/**
  * 使用别名
  */
 public void testQuery4() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //可以使用别名
   List students = session.createQuery("select s.id, s.name from Student s").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }

 

/**
  * 使用别名
  */
 public void testQuery5() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //可以使用as命名别名
   List students = session.createQuery("select s.id, s.name from Student as s").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }

 

 2、实体对象查询【重要】

/**
 * 实体对象查询
 * @author Administrator
 *
 */
public class SimpleObjectQueryTest1 extends TestCase {

 public void testQuery1() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //返回Student对象的集合
   //可以忽略select
   List students = session.createQuery("from Student").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Student student = (Student)iter.next();
    System.out.println(student.getName());
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }
 
 public void testQuery2() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //返回Student对象的集合
   //可以忽略select,表可以使用别名
   List students = session.createQuery("from Student s").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Student student = (Student)iter.next();
    System.out.println(student.getName());
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 } 

 public void testQuery3() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //返回Student对象的集合
   //可以忽略select,表可以使用as命名别名
   List students = session.createQuery("from Student as s").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Student student = (Student)iter.next();
    System.out.println(student.getName());
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }
 
 public void testQuery4() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //返回Student对象的集合
   //使用select查询实体对象，必须采用别名
   List students = session.createQuery("select s from Student as s").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Student student = (Student)iter.next();
    System.out.println(student.getName());
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }  
 
 
 public void testQuery5() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //不支持select * from .....这样的查询语句
   List students = session.createQuery("select * from Student").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Student student = (Student)iter.next();
    System.out.println(student.getName());
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }  
 
}

 

3、条件查询【重要】 

/**
 * 条件查询
 * @author Administrator
 *
 */
public class SimpleConditionQueryTest extends TestCase {

 public void testQuery1() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //可以拼字符串
   List students = session.createQuery("select s.id, s.name from Student s where s.name like '%1%'").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }
 
 public void testQuery2() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
//   Query query = session.createQuery("select s.id, s.name from Student s where s.name like ?");
//   query.setParameter(0, "%1%");
//   List students = query.list();
   
   //可以使用？方式传递参数
   //参数的索引从0开始
   //传递的参数值，不用单引号引起来
   //注意方法链编程
   List students = session.createQuery("select s.id, s.name from Student s where s.name like ?")
               .setParameter(0, "%1%")
               .list();
   
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 } 

 public void testQuery3() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //使用 ：参数名称 的方式传递参数值
   List students = session.createQuery("select s.id, s.name from Student s where s.name like :myname")
               .setParameter("myname", "%1%")
               .list();
   
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }  
 
 public void testQuery4() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //使用 ：参数名称 的方式传递参数值
   List students = session.createQuery("select s.id, s.name from Student s where s.name like :myname and s.id=:myid")
               .setParameter("myname", "%1%")
               .setParameter("myid", 12)
               .list();
   
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }
 
 public void testQuery5() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //支持in，需要使用setParameterList进行参数传递
   List students = session.createQuery("select s.id, s.name from Student s where s.id in(:myids)")
         .setParameterList("myids", new Object[]{1, 2, 3, 4, 5})
               .list();
   
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }   

 public void testQuery6() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //查询2008年2月创建的学生
   List students = session.createQuery("select s.id, s.name from Student s where date_format(s.createTime, '%Y-%m')=?")
         .setParameter(0, "2008-02")
               .list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }   

 public void testQuery7() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
   
   //查询2008-01-10到2008-02-15创建的学生
   List students = session.createQuery("select s.id, s.name from Student s where s.createTime between ? and ?")
         .setParameter(0, sdf.parse("2008-01-10 00:00:00"))
         .setParameter(1, sdf.parse("2008-02-15 23:59:59"))
               .list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }   
}

 

7、分页查询【重要】 
 * setFirstResult()，从0开始
 * setMaxResults,每页显示多少条数据
 参见：PageQueryTest.java

 

/**
 * 分页查询
 * @author Administrator
 *
 */
public class PageQueryTest extends TestCase {

 public void testQuery1() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   List students = session.createQuery("from Student")
         .setFirstResult(1)
         .setMaxResults(2)
         .list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Student student = (Student)iter.next();
    System.out.println(student.getName());
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }  
}

    
8、对象导航查询，在hql中采用 . 进行导航【重要】
 参见：ObjectNavQueryTest.java

 

/**
 * 对象导航查询
 * @author Administrator
 *
 */
public class ObjectNavQueryTest extends TestCase {

 public void testQuery1() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   List students = session.createQuery("select s.name from Student s where s.classes.name like '%1%'").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    String name = (String)iter.next();
    System.out.println(name);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 } 
}

 
9、连接查询【重要】
 * 内连
 * 外连接（左连接/右连接） 
 参见：JoinQueryTest.java

 

/**
 * 连接查询
 * @author Administrator
 *
 */
public class JoinQueryTest extends TestCase {

 public void testQuery1() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   //List students = session.createQuery("select c.name, s.name from Student s join s.classes c").list();
   List students = session.createQuery("select c.name, s.name from Student s inner join s.classes c").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }

 public void testQuery2() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();

   List students = session.createQuery("select c.name, s.name from Classes c left join c.students s").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }
 
 public void testQuery3() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();

   List students = session.createQuery("select c.name, s.name from Classes c right join c.students s").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + "," + obj[1]);
   }
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 }
 
}

 
10、统计查询【重要】
 参见：StatQueryTest.java

 

/**
 * 统计查询
 * @author Administrator
 *
 */
public class StatQueryTest extends TestCase {

 public void testQuery1() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
//   List students =session.createQuery("select count(*) from Student").list();
//   Long count = (Long)students.get(0);
//   System.out.println(count);

   Long count = (Long)session.createQuery("select count(*) from Student").uniqueResult();
   System.out.println(count);
   
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 } 
 
 public void testQuery2() {
  Session session = null;
  try {
   session = HibernateUtils.getSession();
   session.beginTransaction();
   
   List students =session.createQuery("select c.name, count(s) from Student s join s.classes c " +
     "group by c.name order by c.name").list();
   for (Iterator iter=students.iterator(); iter.hasNext();) {
    Object[] obj = (Object[])iter.next();
    System.out.println(obj[0] + ", " + obj[1]);
   }
   
   session.getTransaction().commit();
  }catch(Exception e) {
   e.printStackTrace();
   session.getTransaction().rollback();
  }finally {
   HibernateUtils.closeSession(session);
  }
 } 
 
}