准备
模型及映射文件
package com.zze.bean;
import java.util.HashSet;
import java.util.Set;
public class Class {
public Class() {
}
public Class(Integer id, String name) {
this.id = id;
this.name = name;
}
private Integer id;
private String name;
private Set<Student> students = new HashSet<>();
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set<Student> getStudents() {
return students;
}
public void setStudents(Set<Student> students) {
this.students = students;
}
@Override
public String toString() {
return "Class{" +
"id=" + id +
", name='" + name + '\'' +
'}';
}
}
班级模型：com.zze.bean.Class
<?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="com.zze.bean.Class" table="class">
<id name="id">
<generator class="native"/>
</id>
<property name="name" length="32"/>
<set name="students" cascade="save-update">
<key column="cid"/>
<one-to-many class="com.zze.bean.Student"/>
</set>
</class>
</hibernate-mapping>
班级映射：com/zze/bean/Class.hbm.xml
package com.zze.bean;
import java.util.Date;
import java.util.HashSet;
import java.util.Set;
public class Student {
public Student() {
}
public Student(Integer id, String name, Integer age,String gender) {
this.id = id;
this.name = name;
this.age = age;
this.gender = gender;
}
private Integer id;
private String name;
private Integer age;
private String gender;
private Class clazz;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public Class getClazz() {
return clazz;
}
public void setClazz(Class clazz) {
this.clazz = clazz;
}
@Override
public String toString() {
return "Student{" +
"id=" + id +
", name='" + name + '\'' +
'}';
}
}
学生模型：com.zze.bean.Student
<?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="com.zze.bean.Student" table="student">
<id name="id">
<generator class="native"/>
</id>
<property name="name" length="32"/>
<property name="age"/>
<property name="gender"/>
<many-to-one name="clazz" column="cid" class="com.zze.bean.Class"/>
</class>
</hibernate-mapping>
学生映射：com/zze/bean/Student.hbm.xml
全局配置
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://192.168.208.153:3306/1221</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">root</property>
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.show_sql">true</property>
<property name="hibernate.format_sql">true</property>
<property name="current_session_context_class">thread</property>
<property name="hibernate.hbm2ddl.auto">create</property>
<mapping resource="com/zze/bean/Class.hbm.xml"></mapping>
<mapping resource="com/zze/bean/Student.hbm.xml"></mapping>
</session-factory>
</hibernate-configuration>
hibernate.cfg.xml
工具类
package com.zze.util;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
public static final Configuration cfg;
public static final SessionFactory sf;
static {
cfg = new Configuration().configure();
sf = cfg.buildSessionFactory();
}
public static Session openSession() {
return sf.openSession();
}
public static Session getCurrentSession() {
return sf.getCurrentSession();
}
}
com.zze.util.HibernateUtil
初始化数据
@Test
public void initData(){
Session session = HibernateUtil.getCurrentSession();
Transaction transaction = session.beginTransaction();
Class clazz1 = new Class(null,"软件一班");
Class clazz2 = new Class(null,"软件二班");
Class clazz3 = new Class(null,"汽修一班");
Class clazz4 = new Class(null,"汽修二班");
Student student1 = new Student(null, "张三", 12,"男");
Student student2 = new Student(null, "李四", 13,"女");
Student student3 = new Student(null, "王五", 14,"男");
Student student4 = new Student(null, "赵六", 15,"男");
Student student5 = new Student(null, "吴刚", 39,"男");
Student student6 = new Student(null, "王如花", 30,"女");
Student student7 = new Student(null, "*静", 49,"女");
Student student8 = new Student(null, "何王天", 30,"男");
clazz1.getStudents().add(student1);
clazz1.getStudents().add(student2);
clazz2.getStudents().add(student3);
clazz2.getStudents().add(student4);
clazz3.getStudents().add(student5);
clazz3.getStudents().add(student6);
clazz4.getStudents().add(student7);
clazz4.getStudents().add(student8);
session.save(clazz1);
session.save(clazz2);
session.save(clazz3);
session.save(clazz4);
transaction.commit();
}
init data
几种检索方式
OID检索
-
简介
Hibernate 根据对象的 OID（主键）进行检索。
-
示例
@Test public void test1(){ Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Class clazz = session.get(Class.class, 1); System.out.println(clazz); transaction.commit(); /* Hibernate: select class0_.id as id1_0_0_, class0_.name as name2_0_0_ from class class0_ where class0_.id=? Class{id=1, name='软件一班'} */ }例 1：使用 get 方法
@Test public void test2() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Class clazz = session.load(Class.class, 1); System.out.println(clazz); transaction.commit(); /* Hibernate: select class0_.id as id1_0_0_, class0_.name as name2_0_0_ from class class0_ where class0_.id=? Class{id=1, name='软件一班'} */ }例 2：使用 load 方法
对象导航检索
-
简介
Hibernate 根据一个已经查询到的对象，获得其关联的对象的一种查询方式。
-
示例
@Test public void test3(){ Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Class clazz = session.load(Class.class, 1); System.out.println(clazz); System.out.println(Arrays.toString(clazz.getStudents().toArray())); transaction.commit(); /* Hibernate: select class0_.id as id1_0_0_, class0_.name as name2_0_0_ from class class0_ where class0_.id=? Class{id=1, name='软件一班'} Hibernate: select students0_.cid as cid5_1_0_, students0_.id as id1_1_0_, students0_.id as id1_1_1_, students0_.name as name2_1_1_, students0_.age as age3_1_1_, students0_.gender as gender4_1_1_, students0_.cid as cid5_1_1_ from student students0_ where students0_.cid=? [Student{id=2, name='张三'}, Student{id=1, name='李四'}] */ }例 3：
HQL检索
-
简介
Hibernate Language Query，Hibernate 本身提供语法支持的一种检索方式。
-
示例
/** * 查询所有班级 */ @Test public void test4(){ Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String hql ="from Class"; Query query = session.createQuery(hql); List<Class> list = query.list(); System.out.println(list); transaction.commit(); /* Hibernate: select class0_.id as id1_0_, class0_.name as name2_0_ from class class0_ [Class{id=1, name='软件一班'}, Class{id=2, name='软件二班'}, Class{id=3, name='汽修一班'}, Class{id=4, name='汽修二班'}] */ }例 4：简单查询
@Test public void test5(){ Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String hql ="select c from Class c"; Query query = session.createQuery(hql); List<Class> list = query.list(); System.out.println(list); transaction.commit(); /* Hibernate: select class0_.id as id1_0_, class0_.name as name2_0_ from class class0_ [Class{id=1, name='软件一班'}, Class{id=2, name='软件二班'}, Class{id=3, name='汽修一班'}, Class{id=4, name='汽修二班'}] */ }例 5：别名查询
/** * 根据年龄排序 */ @Test public void test6(){ Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); // 升序 String hql = "from Student order by age"; // 降序 // String hql = "from Student order by age desc"; Query query = session.createQuery(hql); List<Class> list = query.list(); System.out.println(list); transaction.commit(); /* Hibernate: select student0_.id as id1_1_, student0_.name as name2_1_, student0_.age as age3_1_, student0_.gender as gender4_1_, student0_.cid as cid5_1_ from student student0_ order by student0_.age [Student{id=2, name='张三'}, Student{id=1, name='李四'}, Student{id=3, name='王五'}, Student{id=4, name='赵六'}, Student{id=6, name='王如花'}, Student{id=8, name='何王天'}, Student{id=5, name='吴刚'}, Student{id=7, name='*静'}] */ }例 6：排序查询
/** * 一个条件，查询 name='张三' 的 Student * 参数按位置绑定 */ @Test public void test7() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String hql = "from Student where name = ?"; Query query = session.createQuery(hql); query.setParameter(0, "张三"); List<Student> list = query.list(); System.out.println(list); transaction.commit(); /* Hibernate: select student0_.id as id1_1_, student0_.name as name2_1_, student0_.age as age3_1_, student0_.gender as gender4_1_, student0_.cid as cid5_1_ from student student0_ where student0_.name=? [Student{id=2, name='张三'}] */ } /** * 多个条件 查询 name 中包含 '王' 且 age 大于 18 的Student * 参数按名称绑定 */ @Test public void test8() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String hql = "from Student where name like :name and age>:age"; Query query = session.createQuery(hql); query.setParameter("name", "%王%"); query.setParameter("age", 18); List<Student> list = query.list(); System.out.println(list); transaction.commit(); /* Hibernate: select student0_.id as id1_1_, student0_.name as name2_1_, student0_.age as age3_1_, student0_.gender as gender4_1_, student0_.cid as cid5_1_ from student student0_ where ( student0_.name like ? ) and student0_.age>? [Student{id=6, name='王如花'}, Student{id=8, name='何王天'}] */ }例 7：条件查询
/** * 查询单个属性 返回 Object List */ @Test public void test9() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String hql = "select s.name from Student s"; Query query = session.createQuery(hql); List<Object> list = query.list(); System.out.println(list); transaction.commit(); /* Hibernate: select student0_.name as col_0_0_ from student student0_ [李四, 张三, 王五, 赵六, 吴刚, 王如花, *静, 何王天] */ } /** * 查询多个属性 返回 Object[] List */ @Test public void test10() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String hql = "select s.name,s.age from Student s"; Query query = session.createQuery(hql); List<Object[]> list = query.list(); for (Object[] objects : list) { System.out.println(Arrays.toString(objects)); } transaction.commit(); /* Hibernate: select student0_.name as col_0_0_, student0_.age as col_1_0_ from student student0_ [李四, 13] [张三, 12] [王五, 14] [赵六, 15] [吴刚, 39] [王如花, 30] [*静, 49] [何王天, 30] */ } /** * 查询多个属性 返回对应对象类型 List */ @Test public void test11() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); /* 需要让模型提供对应构造： public Student(String name, Integer age) { this.name = name; this.age = age; } */ String hql = "select new Student(name,age) from Student"; Query query = session.createQuery(hql); List<Student> list = query.list(); System.out.println(list); transaction.commit(); /* Hibernate: select student0_.name as col_0_0_, student0_.age as col_1_0_ from student student0_ [Student{id=null, name='李四'}, Student{id=null, name='张三'}, Student{id=null, name='王五'}, Student{id=null, name='赵六'}, Student{id=null, name='吴刚'}, Student{id=null, name='王如花'}, Student{id=null, name='*静'}, Student{id=null, name='何王天'}] */ }例 8：投影查询
@Test public void test12() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String hql = "from Student"; Query query = session.createQuery(hql); query.setFirstResult(0); // 起始行索引 query.setMaxResults(3); // 每页条数 List<Student> list = query.list(); System.out.println(list); transaction.commit(); /* Hibernate: select student0_.id as id1_1_, student0_.name as name2_1_, student0_.age as age3_1_, student0_.gender as gender4_1_, student0_.cid as cid5_1_ from student student0_ limit ? [Student{id=1, name='李四'}, Student{id=2, name='张三'}, Student{id=3, name='王五'}] Process finished with exit code 0 */ }例 9：分页查询
/** * 聚合查询 */ @Test public void test13() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); // 聚合函数使用 count max min avg sum String hql = "select count(1) from Student"; Query query = session.createQuery(hql); Object o = query.uniqueResult(); System.out.println(o.getClass()); System.out.println(o); transaction.commit(); /* Hibernate: select count(1) as col_0_0_ from student student0_ class java.lang.Long 8 */ } /** * 分组查询 返回 Object[] List * 根据 gender 分组，查询每个 gender 的对应数据条数 */ @Test public void test14() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String hql = "select gender,count(1) from Student group by gender"; Query query = session.createQuery(hql); List<Object[]> list = query.list(); for (Object[] objects : list) { System.out.println(Arrays.toString(objects)); } transaction.commit(); /* Hibernate: select student0_.gender as col_0_0_, count(1) as col_1_0_ from student student0_ group by student0_.gender [女, 3] [男, 5] */ }例 10：聚合及分组统计查询
@Test public void test23() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String hql = "from Student c join c.clazz"; Query query = session.createQuery(hql); List<Object[]> list = query.list(); for (Object[] objects : list) { System.out.println(Arrays.toString(objects)); } transaction.commit(); /* Hibernate: select student0_.id as id1_1_0_, class1_.id as id1_0_1_, student0_.name as name2_1_0_, student0_.age as age3_1_0_, student0_.gender as gender4_1_0_, student0_.cid as cid5_1_0_, class1_.name as name2_0_1_ from student student0_ inner join class class1_ on student0_.cid=class1_.id [Student{id=1, name='李四'}, Class{id=1, name='软件一班'}] [Student{id=2, name='张三'}, Class{id=1, name='软件一班'}] [Student{id=3, name='王五'}, Class{id=2, name='软件二班'}] [Student{id=4, name='赵六'}, Class{id=2, name='软件二班'}] [Student{id=5, name='吴刚'}, Class{id=3, name='汽修一班'}] [Student{id=6, name='王如花'}, Class{id=3, name='汽修一班'}] [Student{id=7, name='*静'}, Class{id=4, name='汽修二班'}] [Student{id=8, name='何王天'}, Class{id=4, name='汽修二班'}] */ }例 11：普通内连接
/** * 查询所有学生及其班级 */ @Test public void test24() { /* 迫切内连接 其实就是在普通的内连接 inner join 后添加关键字 fetch 将关联表数据封装到查询对象的属性中 */ Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String hql = "from Student c join fetch c.clazz"; Query query = session.createQuery(hql); List<Student> list = query.list(); for (Student student : list) { System.out.println(String.format("%s %s", student, student.getClazz())); } transaction.commit(); /* Hibernate: select student0_.id as id1_1_0_, class1_.id as id1_0_1_, student0_.name as name2_1_0_, student0_.age as age3_1_0_, student0_.gender as gender4_1_0_, student0_.cid as cid5_1_0_, class1_.name as name2_0_1_ from student student0_ inner join class class1_ on student0_.cid=class1_.id Student{id=1, name='李四'} Class{id=1, name='软件一班'} Student{id=2, name='张三'} Class{id=1, name='软件一班'} Student{id=3, name='王五'} Class{id=2, name='软件二班'} Student{id=4, name='赵六'} Class{id=2, name='软件二班'} Student{id=5, name='吴刚'} Class{id=3, name='汽修一班'} Student{id=6, name='王如花'} Class{id=3, name='汽修一班'} Student{id=7, name='*静'} Class{id=4, name='汽修二班'} Student{id=8, name='何王天'} Class{id=4, name='汽修二班'} */ } /** * 查询所有班级及属于该班级的学生 */ @Test public void test25() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String hql = "select distinct c from Class c join fetch c.students"; Query query = session.createQuery(hql); List<Class> list = query.list(); for (Class clazz : list) { System.out.println(String.format("%s %s", clazz, clazz.getStudents())); } transaction.commit(); /* Class{id=1, name='软件一班'} [Student{id=2, name='张三'}, Student{id=1, name='李四'}] Class{id=2, name='软件二班'} [Student{id=4, name='赵六'}, Student{id=3, name='王五'}] Class{id=3, name='汽修一班'} [Student{id=5, name='吴刚'}, Student{id=6, name='王如花'}] Class{id=4, name='汽修二班'} [Student{id=7, name='*静'}, Student{id=8, name='何王天'}] */ }例 12：迫切内连接
QBC检索
-
简介
Query By Criteria，条件查询，是一种更加面向对象化的查询方式。
-
示例
@Test public void test15(){ Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Criteria criteria = session.createCriteria(Class.class); List<Class> list = criteria.list(); System.out.println(list); transaction.commit(); /* Hibernate: select this_.id as id1_0_0_, this_.name as name2_0_0_ from class this_ [Class{id=1, name='软件一班'}, Class{id=2, name='软件二班'}, Class{id=3, name='汽修一班'}, Class{id=4, name='汽修二班'}] */ }例 13：简单查询
@Test public void test16(){ Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Criteria criteria = session.createCriteria(Class.class); // 升序 criteria.addOrder(Order.asc("id")); // 降序 // criteria.addOrder(Order.desc("id")); List<Class> list = criteria.list(); System.out.println(list); transaction.commit(); /* Hibernate: select this_.id as id1_0_0_, this_.name as name2_0_0_ from class this_ order by this_.id asc [Class{id=1, name='软件一班'}, Class{id=2, name='软件二班'}, Class{id=3, name='汽修一班'}, Class{id=4, name='汽修二班'}] */ }例 14：排序查询
@Test public void test17() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Criteria criteria = session.createCriteria(Student.class); criteria.setFirstResult(0); // 数据起始索引 criteria.setMaxResults(2); // 每页数据条数 List<Student> list = criteria.list(); System.out.println(list); transaction.commit(); /* Hibernate: select this_.id as id1_1_0_, this_.name as name2_1_0_, this_.age as age3_1_0_, this_.gender as gender4_1_0_, this_.cid as cid5_1_0_ from student this_ limit ? [Student{id=1, name='李四'}, Student{id=2, name='张三'}] */ }例 15：分页查询
/** * 简单 and 条件查询 * 查询 name 包含 '王' 且 age>10 */ @Test public void test18() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Criteria criteria = session.createCriteria(Student.class); // 默认多个 criteria.add 的条件是用 and 连接 criteria.add(Restrictions.like("name", "%王%")); criteria.add(Restrictions.gt("age", 10)); List<Student> list = criteria.list(); System.out.println(list); transaction.commit(); /* Hibernate: select this_.id as id1_1_0_, this_.name as name2_1_0_, this_.age as age3_1_0_, this_.gender as gender4_1_0_, this_.cid as cid5_1_0_ from student this_ where this_.name like ? and this_.age>? [Student{id=3, name='王五'}, Student{id=6, name='王如花'}, Student{id=8, name='何王天'}] */ } /** * 简单 or 条件查询 * 查询 name 包含 '王' 或 name 包含 '张' */ @Test public void test19() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Criteria criteria = session.createCriteria(Student.class); // or 条件可以通过 Restrictions.or 方法实现 criteria.add(Restrictions.or(Restrictions.like("name", "%王%"), Restrictions.like("name", "%张%"))); List<Student> list = criteria.list(); System.out.println(list); transaction.commit(); /* Hibernate: select this_.id as id1_1_0_, this_.name as name2_1_0_, this_.age as age3_1_0_, this_.gender as gender4_1_0_, this_.cid as cid5_1_0_ from student this_ where ( this_.name like ? or this_.name like ? ) [Student{id=2, name='张三'}, Student{id=3, name='王五'}, Student{id=6, name='王如花'}, Student{id=8, name='何王天'}] */ } /** * 复杂 and 和 or 查询 * 查询 (name 包含 '王' 且 age>10) 或 name 包含 '张' */ @Test public void test20() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Criteria criteria = session.createCriteria(Student.class); // 通过 conjunction.add 添加的条件是 and 连接 Conjunction conjunction = Restrictions.conjunction(); conjunction.add(Restrictions.like("name", "%王%")); conjunction.add(Restrictions.gt("age", 10)); // 通过 disjunction.add 添加的条件是 or 连接 Disjunction disjunction = Restrictions.disjunction(); disjunction.add(conjunction); disjunction.add(Restrictions.like("name", "%张%")); criteria.add(disjunction); List<Student> list = criteria.list(); System.out.println(list); transaction.commit(); /* Hibernate: select this_.id as id1_1_0_, this_.name as name2_1_0_, this_.age as age3_1_0_, this_.gender as gender4_1_0_, this_.cid as cid5_1_0_ from student this_ where ( ( this_.name like ? and this_.age>? ) or this_.name like ? ) [Student{id=2, name='张三'}, Student{id=3, name='王五'}, Student{id=6, name='王如花'}, Student{id=8, name='何王天'}] */ }例 16：条件查询
/** * 聚合统计查询 * 统计男女人数及最大年龄 */ @Test public void test21() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Criteria criteria = session.createCriteria(Student.class); /* criteria : add : 普通条件，where addOrder : 排序 setProjection : 聚合函数和 group by having */ ProjectionList projectionList = Projections.projectionList(); projectionList.add(Projections.groupProperty("gender")); projectionList.add(Projections.rowCount()); projectionList.add(Projections.max("age")); criteria.setProjection(projectionList); List<Object[]> list = criteria.list(); for (Object[] objects : list) { System.out.println(Arrays.toString(objects)); } transaction.commit(); /* Hibernate: select this_.gender as y0_, count(*) as y1_, max(this_.age) as y2_ from student this_ group by this_.gender [女, 3, 49] [男, 5, 39] */ }例 17：聚合及分组统计查询
/** * 离线条件查询 * 查询 name 包含 '一' */ @Test public void test22(){ DetachedCriteria detachedCriteria = DetachedCriteria.forClass(Class.class); detachedCriteria.add(Restrictions.like("name", "%一%")); Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Criteria criteria = detachedCriteria.getExecutableCriteria(session); List<Class> list = criteria.list(); System.out.println(list); transaction.commit(); /* Hibernate: select this_.id as id1_0_0_, this_.name as name2_0_0_ from class this_ where this_.name like ? [Class{id=1, name='软件一班'}, Class{id=3, name='汽修一班'}] */ }例 18：离线条件查询
SQL检索
-
简介
Hibernate 支持的原生 SQL 查询。
-
示例
/** * 查询所有 Class，返回 Object[] List */ @Test public void test26() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String sql = "select * from class"; SQLQuery sqlQuery = session.createSQLQuery(sql); List<Object[]> list = sqlQuery.list(); for (Object[] objects : list) { System.out.println(Arrays.toString(objects)); } transaction.commit(); /* Hibernate: select * from class [1, 软件一班] [2, 软件二班] [3, 汽修一班] [4, 汽修二班] */ } /** * 查询所有 Class，返回 Class List */ @Test public void test27() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); String sql = "select * from class"; SQLQuery sqlQuery = session.createSQLQuery(sql); sqlQuery.addEntity(Class.class); List<Class> list = sqlQuery.list(); for (Class clazz : list) { System.out.println(clazz); } transaction.commit(); /* Hibernate: select * from class Class{id=1, name='软件一班'} Class{id=2, name='软件二班'} Class{id=3, name='汽修一班'} Class{id=4, name='汽修二班'} */ }例 19：原生 SQL 查询
延迟加载
概述
只有真正使用对象的属性时才会发送 SQL 进行查询。如： session.load(Student.class,1); 。
分类
-
类级别的延迟加载
指的是查询某个类的对象时，针对这个类的对象是否使用延迟加载。
除了修改 lazy="false" 这种方式，还可通过如下两种方式让 lazy 失效：1、将持久化类以 final 修饰。
2、通过调用 Hibernate.initialize(proxy); 。
-
关联级别的延迟加载
指的是查询到某个对象后，再查询其关联的对象是否使用延迟加载。
示例
/**
* 懒加载
* 修改映射文件 ：
* com/zze/bean/Class.hbm.xml :
* <class name="com.zze.bean.Class" table="class" lazy="true">
* lazy 默认为 true
*/
@Test
public void test27() {
Session session = HibernateUtil.getCurrentSession();
Transaction transaction = session.beginTransaction();
Class clazz = session.load(Class.class, 1);
System.out.println(clazz.getClass()); // class com.zze.bean.Class_$$_jvst718_0
System.out.println(clazz); // 发出 SQL
transaction.commit();
}
/**
* 立即加载
* 修改映射文件 :
* com/zze/bean/Class.hbm.xml :
* <class name="com.zze.bean.Class" table="class" lazy="false">
*/
@Test
public void test28() {
Session session = HibernateUtil.getCurrentSession();
Transaction transaction = session.beginTransaction();
Class clazz = session.load(Class.class, 1); // 发出 SQL
System.out.println(clazz.getClass()); // class com.zze.bean.Class
System.out.println(clazz);
transaction.commit();
}
例 20：类级别的延迟加载
/**
* 懒加载
* 修改映射文件 ：
* com/zze/bean/Class.hbm.xml :
* <set name="students" cascade="save-update" lazy="true">
* lazy 默认为 true
*/
@Test
public void test29() {
Session session = HibernateUtil.getCurrentSession();
Transaction transaction = session.beginTransaction();
Class clazz = session.get(Class.class, 1);
Set<Student> students = clazz.getStudents();
System.out.println(students); // 发出 SQL
transaction.commit();
}
/**
* 即时加载
* 修改映射文件 ：
* com/zze/bean/Class.hbm.xml :
* <set name="students" cascade="save-update" lazy="false">
*/
@Test
public void test30() {
Session session = HibernateUtil.getCurrentSession();
Transaction transaction = session.beginTransaction();
Class clazz = session.get(Class.class, 1);
Set<Student> students = clazz.getStudents(); // 发出 SQL
System.out.println(students);
transaction.commit();
}
/**
* 懒加载
* 修改映射文件 :
* com/zze/bean/Student.hbm.xml :
* <many-to-one name="clazz" lazy="proxy" column="cid" class="com.zze.bean.Class"/>
* com/zze/bean/Class.hbm.xml :
* <class name="com.zze.bean.Class" table="class" lazy="true">
* <p>
* proxy : 默认值，表示引用关联类的加载策略。
*/
@Test
public void test31() {
Session session = HibernateUtil.getCurrentSession();
Transaction transaction = session.beginTransaction();
Student student = session.get(Student.class, 1);
Class clazz = student.getClazz();
System.out.println(clazz); // 发出 SQL
transaction.commit();
}
/**
* 即时加载
* 当关联类的 lazy="false" 时，无论当前类 many-to-one 标签上的 lazy 如何配置，都是即时加载。
* 修改映射文件 :
* com/zze/bean/Student.hbm.xml :
* * <many-to-one name="clazz" lazy="proxy" column="cid" class="com.zze.
* com/zze/bean/Class.hbm.xml :
* * <class name="com.zze.bean.Class" table="class" lazy="false">
* 或 :
* com/zze/bean/Student.hbm.xml :
* * <many-to-one name="clazz" lazy="false" column="cid" class="com.zze.bean.Class"/>
* com/zze/bean/Class.hbm.xml :
* * <class name="com.zze.bean.Class" table="class" lazy="true">
*/
@Test
public void test32() {
Session session = HibernateUtil.getCurrentSession();
Transaction transaction = session.beginTransaction();
Student student = session.get(Student.class, 1);
Class clazz = student.getClazz(); // 发出 SQL
System.out.println(clazz);
transaction.commit();
}
例 21：关联级别的延迟加载
抓取策略
概述
通过一个对象抓取关联对象需要发送 SQL ，SQL 如何发送及 SQL 的发送规则就可以通过抓取策略进行配置。
通过 <set> 或 <many-to-one> 上的 fetch 属性进行配置。
要考虑fetch 和这些标签上的 lazy 如何配置才能最大化优化发送的 SQL 语句。
set标签上的fetch和lazy
-
fetch
抓取策略，控制 SQL 语句格式。
在这里 fetch 有三个可选值：
select : 默认值，发送普通 select 语句查询关联对象。
join: 发送一条迫切左外连接查询关联对象。
subselect : 发送子查询查询关联对象。
-
lazy
延迟加载，控制查询关联对象时是否使用懒加载。
在这里 lazy 有三个可选值：
true : 默认值，查询关联对象时，使用延迟加载。
false : 查询关联对象时，不使用延迟加载。
extra : 及其懒惰。
-
示例
/** * com/zze/bean/Class.hbm.xml * 默认值： * <set name="students" cascade="save-update" fetch="select" lazy="true"> */ @Test public void test33() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Class clazz = session.get(Class.class, 1); for (Student student : clazz.getStudents()) { System.out.println(student);// 发送 SQL } transaction.commit(); /* Hibernate: select class0_.id as id1_0_0_, class0_.name as name2_0_0_ from class class0_ where class0_.id=? Hibernate: select students0_.cid as cid5_1_0_, students0_.id as id1_1_0_, students0_.id as id1_1_1_, students0_.name as name2_1_1_, students0_.age as age3_1_1_, students0_.gender as gender4_1_1_, students0_.cid as cid5_1_1_ from student students0_ where students0_.cid=? Student{id=2, name='张三'} Student{id=1, name='李四'} */ } /** * com/zze/bean/Class.hbm.xml * * <set name="students" cascade="save-update" fetch="select" lazy="false"> */ @Test public void test34() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Class clazz = session.get(Class.class, 1); //发送 2 条 SQL for (Student student : clazz.getStudents()) { System.out.println(student); } transaction.commit(); /* Hibernate: select class0_.id as id1_0_0_, class0_.name as name2_0_0_ from class class0_ where class0_.id=? Hibernate: select students0_.cid as cid5_1_0_, students0_.id as id1_1_0_, students0_.id as id1_1_1_, students0_.name as name2_1_1_, students0_.age as age3_1_1_, students0_.gender as gender4_1_1_, students0_.cid as cid5_1_1_ from student students0_ where students0_.cid=? Student{id=2, name='张三'} Student{id=1, name='李四'} */ } /** * com/zze/bean/Class.hbm.xml * * <set name="students" cascade="save-update" fetch="select" lazy="extra"> */ @Test public void test35() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Class clazz = session.get(Class.class, 1); System.out.println(clazz.getStudents().size()); // 针对数量发送一条sql transaction.commit(); /* Hibernate: select class0_.id as id1_0_0_, class0_.name as name2_0_0_ from class class0_ where class0_.id=? Hibernate: select count(id) from student where cid =? */ } /** * com/zze/bean/Class.hbm.xml * fetch="join" 时，lazy 失效 * <set name="students" cascade="save-update" fetch="join" lazy="true"> */ public void test36() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Class clazz = session.get(Class.class, 1);// 发送 SQL for (Student student : clazz.getStudents()) { System.out.println(student); } transaction.commit(); /* Hibernate: select class0_.id as id1_0_0_, class0_.name as name2_0_0_, students1_.cid as cid5_1_1_, students1_.id as id1_1_1_, students1_.id as id1_1_2_, students1_.name as name2_1_2_, students1_.age as age3_1_2_, students1_.gender as gender4_1_2_, students1_.cid as cid5_1_2_ from class class0_ left outer join student students1_ on class0_.id=students1_.cid where class0_.id=? Student{id=2, name='张三'} Student{id=1, name='李四'} */ } /** * com/zze/bean/Class.hbm.xml * * <set name="students" cascade="save-update" fetch="subselect" lazy="true"> */ @Test public void test37() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Query query = session.createQuery("from Class"); List<Class> list = query.list(); for (Class clazz : list) { Set<Student> students = clazz.getStudents(); // 发送 SQL System.out.println(students); } transaction.commit(); /* Hibernate: select class0_.id as id1_0_, class0_.name as name2_0_ from class class0_ Hibernate: select students0_.cid as cid5_1_1_, students0_.id as id1_1_1_, students0_.id as id1_1_0_, students0_.name as name2_1_0_, students0_.age as age3_1_0_, students0_.gender as gender4_1_0_, students0_.cid as cid5_1_0_ from student students0_ where students0_.cid in ( select class0_.id from class class0_ ) [Student{id=1, name='李四'}, Student{id=2, name='张三'}] [Student{id=4, name='赵六'}, Student{id=3, name='王五'}] [Student{id=5, name='吴刚'}, Student{id=6, name='王如花'}] [Student{id=7, name='*静'}, Student{id=8, name='何王天'}] */ } /** * com/zze/bean/Class.hbm.xml * * <set name="students" cascade="save-update" fetch="subselect" lazy="false"> */ @Test public void test38() { Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Query query = session.createQuery("from Class"); List<Class> list = query.list(); // 发送 SQL for (Class clazz : list) { Set<Student> students = clazz.getStudents(); System.out.println(students); } transaction.commit(); /* Hibernate: select class0_.id as id1_0_, class0_.name as name2_0_ from class class0_ Hibernate: select students0_.cid as cid5_1_1_, students0_.id as id1_1_1_, students0_.id as id1_1_0_, students0_.name as name2_1_0_, students0_.age as age3_1_0_, students0_.gender as gender4_1_0_, students0_.cid as cid5_1_0_ from student students0_ where students0_.cid in ( select class0_.id from class class0_ ) [Student{id=1, name='李四'}, Student{id=2, name='张三'}] [Student{id=4, name='赵六'}, Student{id=3, name='王五'}] [Student{id=5, name='吴刚'}, Student{id=6, name='王如花'}] [Student{id=7, name='*静'}, Student{id=8, name='何王天'}] */ }例 22：
many-to-one上的fetch和lazy
-
fetch
抓取策略，控制 SQL 语句格式。
在这里 fetch 有两个可选值：
select : 默认值，发送普通的 select 语句查询关联对象。
join : 发送一条迫切左外连接查询关联对象。
-
lazy
延迟加载，控制查询关联对象时是否使用懒加载。
在这里 lazy 有三个可选值：
proxy : 默认值，引用关联对象类的类级别加载策略。
flase : 查询关联对象时，不使用延迟加载。
no-proxy：不使用。
-
示例
/** * com/zze/bean/Student.hbm.xml * 默认值 * <many-to-one name="clazz" column="cid" class="com.zze.bean.Class" fetch="select" lazy="proxy"/> * * com/zze/bean/Class.hbm.xml * <class name="com.zze.bean.Class" table="class" lazy="true"> */ @Test public void test39(){ Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Student student = session.get(Student.class, 1); System.out.println(student.getClazz()); // 发送 SQL transaction.commit(); /* Hibernate: select student0_.id as id1_1_0_, student0_.name as name2_1_0_, student0_.age as age3_1_0_, student0_.gender as gender4_1_0_, student0_.cid as cid5_1_0_ from student student0_ where student0_.id=? Hibernate: select class0_.id as id1_0_0_, class0_.name as name2_0_0_ from class class0_ where class0_.id=? Class{id=1, name='软件一班'} */ } /** * com/zze/bean/Student.hbm.xml * 默认值 * <many-to-one name="clazz" column="cid" class="com.zze.bean.Class" fetch="select" lazy="proxy"/> * * com/zze/bean/Class.hbm.xml * <class name="com.zze.bean.Class" table="class" lazy="false"> */ @Test public void test40(){ Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Student student = session.get(Student.class, 1);// 一次发送 2 条 SQL System.out.println(student.getClazz()); transaction.commit(); /* Hibernate: select student0_.id as id1_1_0_, student0_.name as name2_1_0_, student0_.age as age3_1_0_, student0_.gender as gender4_1_0_, student0_.cid as cid5_1_0_ from student student0_ where student0_.id=? Hibernate: select class0_.id as id1_0_0_, class0_.name as name2_0_0_ from class class0_ where class0_.id=? Class{id=1, name='软件一班'} */ } /** * com/zze/bean/Student.hbm.xml * fetch="join" 时，lazy 失效 * <many-to-one name="clazz" column="cid" class="com.zze.bean.Class" fetch="join" lazy="proxy"/> */ @Test public void test41(){ Session session = HibernateUtil.getCurrentSession(); Transaction transaction = session.beginTransaction(); Student student = session.get(Student.class, 1);// 一条关联 SQL System.out.println(student.getClazz()); transaction.commit(); /* Hibernate: select student0_.id as id1_1_0_, student0_.name as name2_1_0_, student0_.age as age3_1_0_, student0_.gender as gender4_1_0_, student0_.cid as cid5_1_0_, class1_.id as id1_0_1_, class1_.name as name2_0_1_ from student student0_ left outer join class class1_ on student0_.cid=class1_.id where student0_.id=? Class{id=1, name='软件一班'} */ }例 23：
批量抓取
一批指定数量的关联数据一起查询。
/**
* 查询所有班级 及 所有班级下的学生信息
* 默认情况下，查询所有班级会发一条 SQL，然后每次查询班级上的学生也会发送一条 SQL
* 即如下有 4 个班级，会发 5 条SQL
*/
@Test
public void test42() {
Session session = HibernateUtil.getCurrentSession();
Transaction transaction = session.beginTransaction();
Query query = session.createQuery("from Class");
List<Class> list = query.list();
for (Class clazz : list) {
System.out.println(clazz);
for (Student student : clazz.getStudents()) {
System.out.println(student);
}
}
transaction.commit();
/*
Hibernate:
select
class0_.id as id1_0_,
class0_.name as name2_0_
from
class class0_
Class{id=1, name='软件一班'}
Hibernate:
select
students0_.cid as cid5_1_0_,
students0_.id as id1_1_0_,
students0_.id as id1_1_1_,
students0_.name as name2_1_1_,
students0_.age as age3_1_1_,
students0_.gender as gender4_1_1_,
students0_.cid as cid5_1_1_
from
student students0_
where
students0_.cid=?
Student{id=1, name='李四'}
Student{id=2, name='张三'}
Class{id=2, name='软件二班'}
Hibernate:
select
students0_.cid as cid5_1_0_,
students0_.id as id1_1_0_,
students0_.id as id1_1_1_,
students0_.name as name2_1_1_,
students0_.age as age3_1_1_,
students0_.gender as gender4_1_1_,
students0_.cid as cid5_1_1_
from
student students0_
where
students0_.cid=?
Student{id=4, name='王五'}
Student{id=3, name='赵六'}
Class{id=3, name='汽修一班'}
Hibernate:
select
students0_.cid as cid5_1_0_,
students0_.id as id1_1_0_,
students0_.id as id1_1_1_,
students0_.name as name2_1_1_,
students0_.age as age3_1_1_,
students0_.gender as gender4_1_1_,
students0_.cid as cid5_1_1_
from
student students0_
where
students0_.cid=?
Student{id=5, name='王如花'}
Student{id=6, name='吴刚'}
Class{id=4, name='汽修二班'}
Hibernate:
select
students0_.cid as cid5_1_0_,
students0_.id as id1_1_0_,
students0_.id as id1_1_1_,
students0_.name as name2_1_1_,
students0_.age as age3_1_1_,
students0_.gender as gender4_1_1_,
students0_.cid as cid5_1_1_
from
student students0_
where
students0_.cid=?
Student{id=8, name='*静'}
Student{id=7, name='何王天'}
*/
}
/**
* com/zze/bean/Class.hbm.xml
*
* <set name="students" cascade="save-update" batch-size="4">
* <p>
* 一次抓取 4 条，就只需要发送 2 次 SQL
* 一次查询所有班级，一次查询所有班级下的学生
*/
@Test
public void test43() {
Session session = HibernateUtil.getCurrentSession();
Transaction transaction = session.beginTransaction();
Query query = session.createQuery("from Class");
List<Class> list = query.list();
for (Class clazz : list) {
System.out.println(clazz);
for (Student student : clazz.getStudents()) {
System.out.println(student);
}
}
transaction.commit();
/*
Hibernate:
select
class0_.id as id1_0_,
class0_.name as name2_0_
from
class class0_
Class{id=1, name='软件一班'}
Hibernate:
select
students0_.cid as cid5_1_1_,
students0_.id as id1_1_1_,
students0_.id as id1_1_0_,
students0_.name as name2_1_0_,
students0_.age as age3_1_0_,
students0_.gender as gender4_1_0_,
students0_.cid as cid5_1_0_
from
student students0_
where
students0_.cid in (
?, ?, ?, ?
)
Student{id=1, name='李四'}
Student{id=2, name='张三'}
Class{id=2, name='软件二班'}
Student{id=4, name='王五'}
Student{id=3, name='赵六'}
Class{id=3, name='汽修一班'}
Student{id=5, name='王如花'}
Student{id=6, name='吴刚'}
Class{id=4, name='汽修二班'}
Student{id=7, name='何王天'}
Student{id=8, name='*静'}
*/
}
/**
* 查询所有学生 及 所有学生所属班级信息
* 默认情况下，查询所有学生会发送 1 条 SQL，然后每次查询每个学生的所属班级时也会发送一条 SQL，
* 有 8 个学生，但一共有 4 个班级，由于一级缓存的作用，查询班级需要发送 4 条 SQL
* 共发 5 条 SQL
*/
@Test
public void test44() {
Session session = HibernateUtil.getCurrentSession();
Transaction transaction = session.beginTransaction();
Query query = session.createQuery("from Student");
List<Student> list = query.list();
for (Student student : list) {
System.out.println(student.getClazz());
}
transaction.commit();
/*
Hibernate:
select
student0_.id as id1_1_,
student0_.name as name2_1_,
student0_.age as age3_1_,
student0_.gender as gender4_1_,
student0_.cid as cid5_1_
from
student student0_
Hibernate:
select
class0_.id as id1_0_0_,
class0_.name as name2_0_0_
from
class class0_
where
class0_.id=?
Class{id=1, name='软件一班'}
Class{id=1, name='软件一班'}
Hibernate:
select
class0_.id as id1_0_0_,
class0_.name as name2_0_0_
from
class class0_
where
class0_.id=?
Class{id=2, name='软件二班'}
Class{id=2, name='软件二班'}
Hibernate:
select
class0_.id as id1_0_0_,
class0_.name as name2_0_0_
from
class class0_
where
class0_.id=?
Class{id=3, name='汽修一班'}
Class{id=3, name='汽修一班'}
Hibernate:
select
class0_.id as id1_0_0_,
class0_.name as name2_0_0_
from
class class0_
where
class0_.id=?
Class{id=4, name='汽修二班'}
Class{id=4, name='汽修二班'}
*/
}
/**
* com/zze/bean/Class.hbm.xml
* <class name="com.zze.bean.Class" table="class" batch-size="3">
* <p>
* many-to-one 关系时需在关联属性类映射文件下配置 batch-size
* <p>
* 查询所有学生 1 条 SQL，查询所有班级每次抓取 3 条，一共 4 个班级，会发 2 次 SQL
*/
@Test
public void test45() {
Session session = HibernateUtil.getCurrentSession();
Transaction transaction = session.beginTransaction();
Query query = session.createQuery("from Student");
List<Student> list = query.list();
for (Student student : list) {
System.out.println(student.getClazz());
}
transaction.commit();
/*
Hibernate:
select
student0_.id as id1_1_,
student0_.name as name2_1_,
student0_.age as age3_1_,
student0_.gender as gender4_1_,
student0_.cid as cid5_1_
from
student student0_
Hibernate:
select
class0_.id as id1_0_0_,
class0_.name as name2_0_0_
from
class class0_
where
class0_.id in (
?, ?, ?
)
Class{id=1, name='软件一班'}
Class{id=1, name='软件一班'}
Class{id=2, name='软件二班'}
Class{id=2, name='软件二班'}
Class{id=3, name='汽修一班'}
Class{id=3, name='汽修一班'}
Hibernate:
select
class0_.id as id1_0_0_,
class0_.name as name2_0_0_
from
class class0_
where
class0_.id=?
Class{id=4, name='汽修二班'}
Class{id=4, name='汽修二班'}
*/
}
例 24：