Java持久层之Hibernate：05_Hibernate查询方式

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对象导航查询：	根据id查询某个客户，再查询这个客户里面所有的联系人
OID查询：		根据id查询某一条记录，返回对象
HQL查询：		Query对象，写HQL语句实现查询
QBC查询：		Criteria对象
本地SQL查询：	SQLQuery对象，使用普通SQL实现查询

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实体类的实现

• 客户实体类

package com.ycom1024.hernate.po;

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

public class Customer {
	private Integer id;
	private String name;
	private String level;
	private String source;
	private String phone;
	private String mobile;
	
	private Set<LinkMan> linkMans = 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 String getLevel() {
		return level;
	}

	public void setLevel(String level) {
		this.level = level;
	}

	public String getSource() {
		return source;
	}

	public void setSource(String source) {
		this.source = source;
	}

	public String getPhone() {
		return phone;
	}

	public void setPhone(String phone) {
		this.phone = phone;
	}

	public String getMobile() {
		return mobile;
	}

	public void setMobile(String mobile) {
		this.mobile = mobile;
	}

	public Set<LinkMan> getLinkMans() {
		return linkMans;
	}

	public void setLinkMans(Set<LinkMan> linkMans) {
		this.linkMans = linkMans;
	}

	/**
	 * 注意: 没有打印linkMans的信息
	 */
	@Override
	public String toString() {
		return "Customer [id=" + id + ", name=" + name + ", level=" + level + ", source=" + source + ", phone=" + phone
				+ ", mobile=" + mobile + "]";
	}
}

• 联系人实体类

package com.ycom1024.hernate.po;

public class LinkMan {
	private Integer id;
	private String name;
	private String gender;
	private String phone;
	
	private Customer customer;

	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 String getGender() {
		return gender;
	}

	public void setGender(String gender) {
		this.gender = gender;
	}

	public String getPhone() {
		return phone;
	}

	public void setPhone(String phone) {
		this.phone = phone;
	}

	public Customer getCustomer() {
		return customer;
	}

	public void setCustomer(Customer customer) {
		this.customer = customer;
	}

	/**
	 * 注意: 没有打印customer的信息
	 */
	@Override
	public String toString() {
		return "LinkMan [id=" + id + ", name=" + name + ", gender=" + gender + ", phone=" + phone + "]";
	}
}

---

对象导航查询

• 代码实现

@Test
public void testQuery1() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// 对象导航查询
	Customer customer = session.get(Customer.class, 11);
	Set<LinkMan> linkMans = customer.getLinkMans();
	for (LinkMan linkMan : linkMans) {
		System.out.println(linkMan);
	}
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
-----------------------------------------------------------------------------
Hibernate: 
    select
        customer0_.id as id1_0_0_,
        customer0_.name as name2_0_0_,
        customer0_.level as level3_0_0_,
        customer0_.source as source4_0_0_,
        customer0_.phone as phone5_0_0_,
        customer0_.mobile as mobile6_0_0_ 
    from
        t_customer customer0_ 
    where
        customer0_.id=?
Hibernate: 
    select
        linkmans0_.fk_limlman_customer as fk_limlm5_1_0_,
        linkmans0_.id as id1_1_0_,
        linkmans0_.id as id1_1_1_,
        linkmans0_.name as name2_1_1_,
        linkmans0_.gender as gender3_1_1_,
        linkmans0_.phone as phone4_1_1_,
        linkmans0_.fk_limlman_customer as fk_limlm5_1_1_ 
    from
        t_linkman linkmans0_ 
    where
        linkmans0_.fk_limlman_customer=?
LinkMan [id=23, name=M3, gender=null, phone=null]
LinkMan [id=22, name=M1, gender=male, phone=123456]

---

OID查询

• 根据id查询就是OID查询
• 代码实现：

@Test
public void testQuery2() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// OD查询
	Customer customer = session.get(Customer.class, 11);
	System.out.println(customer);
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
-----------------------------------------------------------------------------
Hibernate: 
    select
        customer0_.id as id1_0_0_,
        customer0_.name as name2_0_0_,
        customer0_.level as level3_0_0_,
        customer0_.source as source4_0_0_,
        customer0_.phone as phone5_0_0_,
        customer0_.mobile as mobile6_0_0_ 
    from
        t_customer customer0_ 
    where
        customer0_.id=?
Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]

HQL查询

• HQL：Hibernate Query Language：Hibernate提供一种查询语言，HQ;语言和普通的SQL很相似：区别：普通的SQL操作数据库的表与字段；HQL操作的是实体类与属性
• 常用的HQL语句
  （1） 查询所有
  （2） 条件查询
  （3） 排序查询
  （4） 分页查询
  （5） 投影查询
  （6） 聚合函数使用
• 使用HQL查询操作的时候使用Query对象
  （1） 创建Query对象：使用HQL语句来创建Query对象
  （2） 调用Query对象里面的方法得到结果

查询所有

• HQL语法：from 实体类名
• 代码实现

@Test
public void testQuery3() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// HQL查询: 查询所有
	Query query = session.createQuery("from Customer");
	List<Customer> customers = query.list();
	System.out.println(customers);
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
-----------------------------------------------------------------------------
Hibernate: 
    select
        customer0_.id as id1_0_,
        customer0_.name as name2_0_,
        customer0_.level as level3_0_,
        customer0_.source as source4_0_,
        customer0_.phone as phone5_0_,
        customer0_.mobile as mobile6_0_ 
    from
        t_customer customer0_
[Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456], Customer [id=12, name=BBBBB, level=null, source=null, phone=null, mobile=null]]

条件查询

• HQL语法：from 实体类名称 where 实体类属性名称 = ? and 实体类属性名称 = ?
• HQL语法：from 实体类名称 where 实体类属性名称 like ?
• 代码实现：

@Test
public void testQuery4() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// HQL查询: 条件查询
	Query query = session.createQuery("from Customer where id = ? and phone = ?");
	query.setParameter(0, 11);
	query.setParameter(1, "110");
	List<Customer> customers = query.list();
	System.out.println(customers);
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
---------------------------------------------------------------------------------
Hibernate: 
    select
        customer0_.id as id1_0_,
        customer0_.name as name2_0_,
        customer0_.level as level3_0_,
        customer0_.source as source4_0_,
        customer0_.phone as phone5_0_,
        customer0_.mobile as mobile6_0_ 
    from
        t_customer customer0_ 
    where
        customer0_.id=? 
        and customer0_.phone=?
[Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]]

排序查询

HQL语法：from 实体类名称 order by 实体类属性名称 asc/desc

• 代码实现：

@Test
public void testQuery5() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// HQL查询: 排序查询
	Query query = session.createQuery("from Customer order by id desc");
	List<Customer> customers = query.list();
	System.out.println(customers);
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
------------------------------------------------------------------------------------
Hibernate: 
    select
        customer0_.id as id1_0_,
        customer0_.name as name2_0_,
        customer0_.level as level3_0_,
        customer0_.source as source4_0_,
        customer0_.phone as phone5_0_,
        customer0_.mobile as mobile6_0_ 
    from
        t_customer customer0_ 
    order by
        customer0_.id desc
[Customer [id=12, name=BBBBB, level=null, source=null, phone=null, mobile=null], Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]]

分页查询

• MySQL数据库实现分页查询：使用关键字limit
• 在HQL中实现分页就不能写limit！Hibernate的Query对象封装了两个方法实现分页操作
• 代码实现

@Test
public void testQuery6() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// HQL查询: 分页查询
	Query query = session.createQuery("from Customer");
	// 设置分页的起始位置
	query.setFirstResult(0);
	// 设置分页查询的每页记录数
	query.setMaxResults(1);
	List<Customer> customers = query.list();
	System.out.println(customers);
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
---------------------------------------------------------------------------------
Hibernate: 
    select
        customer0_.id as id1_0_,
        customer0_.name as name2_0_,
        customer0_.level as level3_0_,
        customer0_.source as source4_0_,
        customer0_.phone as phone5_0_,
        customer0_.mobile as mobile6_0_ 
    from
        t_customer customer0_ limit ?
[Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]]

投影查询

• 投影查询：查询的不是所有字段，而是部分字段
• HQL语法：select 实体类属性名称1, 实体类属性名称2 from 实体类名称;
• 注意：HQL查询中的select语句是不能写*的，即不支持select *写法
• 代码实现

@Test
public void testQuery7() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// HQL查询: 投影查询：查询部分字段
	Query query = session.createQuery("select name from Customer");
	List<Customer> customers = query.list();
	System.out.println(customers);
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
-----------------------------------------------------------------------------
Hibernate: 
    select
        customer0_.name as col_0_0_ 
    from
        t_customer customer0_
[AAAAA, BBBBB]

聚合函数查询

• 常用的聚合函数：count、sum、avg、max、min
• HQL语法：select count(*) from 实体类名称
• 代码实现

@Test
public void testQuery8() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// HQL查询: 聚合函数的使用
	Query query = session.createQuery("select count(*) from Customer");
	Object result = query.uniqueResult(); //Query#uniqueResult()方法返回值为Long
	int cnt = ((Long)result).intValue();
	System.out.println(cnt);
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
-----------------------------------------------------------------------
Hibernate: 
    select
        count(*) as col_0_0_ 
    from
        t_customer customer0_
2

---

QBC查询

• 使用HQL查询需要些HQL语句实现，但是使用QBC查询的时候就不需要再写语句了。使用方法实现
• 使用QBC操作的时候操作的是实体类及其属性
• 使用QBC查询使用的是Criteria对象实现

查询所有

@Test
public void testQuery9() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// 创建Criteria对象
	Criteria criteria = session.createCriteria(Customer.class);
	// 调用Criteria对象的方法得到结果
	List<Customer> customers = criteria.list();
	System.out.println(customers);
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
------------------------------------------------------------------------
Hibernate: 
    select
        this_.id as id1_0_0_,
        this_.name as name2_0_0_,
        this_.level as level3_0_0_,
        this_.source as source4_0_0_,
        this_.phone as phone5_0_0_,
        this_.mobile as mobile6_0_0_ 
    from
        t_customer this_
[Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456], Customer [id=12, name=BBBBB, level=null, source=null, phone=null, mobile=null]]

条件查询

@Test
public void testQuery10() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// 创建Criteria对象
	Criteria criteria = session.createCriteria(Customer.class);
	// 添加条件
	criteria.add(Restrictions.eq("id", 11));
	criteria.add(Restrictions.eq("name", "AAAAA"));
	// 调用Criteria对象的方法得到结果
	List<Customer> customers = criteria.list();
	System.out.println(customers);
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
--------------------------------------------------------------------------------
Hibernate: 
    select
        this_.id as id1_0_0_,
        this_.name as name2_0_0_,
        this_.level as level3_0_0_,
        this_.source as source4_0_0_,
        this_.phone as phone5_0_0_,
        this_.mobile as mobile6_0_0_ 
    from
        t_customer this_ 
    where
        this_.id=? 
        and this_.name=?
[Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]]

短语	含义
Restrictions.eq	等于=
Restrictions.allEq	使用Map，使用key:value进行多个等于的判断
Restrictions.gt	大于>
Restrictions.ge	大于等于>=
Restrictions.lt	小于<
Restrictions.le	小于等于<=
Restrictions.between	对应SQL语句的between子句
Restrictions.like	对应SQL语句的like子句
Restrictions.in	对应SQL语句的in子句
Restrictions.and	and关系
Restrictions.or	or关系
Restrictions.sqlRestriction	SQL限定查询
Order.asc	根据传入的字段升序排列
Order.desc	根据传入的字段降序排列

排序查询

@Test
public void testQuery11() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// 创建Criteria对象
	Criteria criteria = session.createCriteria(Customer.class);
	// 添加条件
	criteria.addOrder(Order.desc("name"));
	// 调用Criteria对象的方法得到结果
	List<Customer> customers = criteria.list();
	System.out.println(customers);
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
--------------------------------------------------------------------------------
Hibernate: 
    select
        this_.id as id1_0_0_,
        this_.name as name2_0_0_,
        this_.level as level3_0_0_,
        this_.source as source4_0_0_,
        this_.phone as phone5_0_0_,
        this_.mobile as mobile6_0_0_ 
    from
        t_customer this_ 
    order by
        this_.name desc
[Customer [id=12, name=BBBBB, level=null, source=null, phone=null, mobile=null], Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]]

分页查询

@Test
public void testQuery12() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// 创建Criteria对象
	Criteria criteria = session.createCriteria(Customer.class);
	criteria.setFirstResult(0);
	criteria.setMaxResults(1);
	// 调用Criteria对象的方法得到结果
	List<Customer> customers = criteria.list();
	System.out.println(customers);
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
------------------------------------------------------------------------------------
Hibernate: 
    select
        this_.id as id1_0_0_,
        this_.name as name2_0_0_,
        this_.level as level3_0_0_,
        this_.source as source4_0_0_,
        this_.phone as phone5_0_0_,
        this_.mobile as mobile6_0_0_ 
    from
        t_customer this_ limit ?
[Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]]

统计查询

@Test
public void testQuery13() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	// 创建Criteria对象
	Criteria criteria = session.createCriteria(Customer.class);
	criteria.setProjection(Projections.rowCount());
	// 调用Criteria对象的方法得到结果
	Long ret = (Long)criteria.uniqueResult();
	System.out.println(ret.intValue());
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
---------------------------------------------------------------------------------
Hibernate: 
    select
        count(*) as y0_ 
    from
        t_customer this_
2

离线查询

---

HQL多表查询

• 内连接查询
• 左外连接查询
• 右外连接查询
• 迫切内连接查询
• 迫切左外连接查询

HQL内连接查询

• HQL语法：from Customer c inner join c.linkMans：连接条件：外键

@Test
public void testQuery14() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	Query query = session.createQuery("from Customer c inner join c.linkMans");
	List objs = query.list(); // List集合的元素是数组
	for (int i = 0; i < objs.size(); i++) {
		Object[] obj = (Object[])(objs.get(i));
		for (Object o : obj) {
			System.out.println(o);
		}
		System.out.println("------------------------------");
	}
	
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
----------------------------------------------------------------------------
Hibernate: 
    select
        customer0_.id as id1_0_0_,
        linkmans1_.id as id1_1_1_,
        customer0_.name as name2_0_0_,
        customer0_.level as level3_0_0_,
        customer0_.source as source4_0_0_,
        customer0_.phone as phone5_0_0_,
        customer0_.mobile as mobile6_0_0_,
        linkmans1_.name as name2_1_1_,
        linkmans1_.gender as gender3_1_1_,
        linkmans1_.phone as phone4_1_1_,
        linkmans1_.fk_limlman_customer as fk_limlm5_1_1_ 
    from
        t_customer customer0_ 
    inner join
        t_linkman linkmans1_ 
            on customer0_.id=linkmans1_.fk_limlman_customer
Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]
LinkMan [id=22, name=M1, gender=male, phone=123456]
------------------------------
Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]
LinkMan [id=23, name=M3, gender=null, phone=null]
------------------------------
Customer [id=12, name=BBBBB, level=null, source=null, phone=null, mobile=null]
LinkMan [id=21, name=M2, gender=female, phone=12345678]
------------------------------

迫切内连接查询

• 迫切内连接查询和内连接查询的底层实现是一样的
• 区别：使用内连接查询返回的List集合中的元素是数组；而使用迫切内连接查询返回的List集合的元素是对象
• HQL语法：from Customer c inner join fetch c.linkMans：连接条件：外键

@Test
public void testQuery15() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	Query query = session.createQuery("from Customer c inner join fetch c.linkMans");
	List<Customer> customers = query.list();
	
	System.out.println("----------------------------");
	for (Customer customer : customers) {
		System.out.println(customer);
		System.out.println(customer.getLinkMans());
		System.out.println("----------------------------");
	}
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
------------------------------------------------------------------------------------
Hibernate: 
    select
        customer0_.id as id1_0_0_,
        linkmans1_.id as id1_1_1_,
        customer0_.name as name2_0_0_,
        customer0_.level as level3_0_0_,
        customer0_.source as source4_0_0_,
        customer0_.phone as phone5_0_0_,
        customer0_.mobile as mobile6_0_0_,
        linkmans1_.name as name2_1_1_,
        linkmans1_.gender as gender3_1_1_,
        linkmans1_.phone as phone4_1_1_,
        linkmans1_.fk_limlman_customer as fk_limlm5_1_1_,
        linkmans1_.fk_limlman_customer as fk_limlm5_1_0__,
        linkmans1_.id as id1_1_0__ 
    from
        t_customer customer0_ 
    inner join
        t_linkman linkmans1_ 
            on customer0_.id=linkmans1_.fk_limlman_customer
----------------------------
Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]
[LinkMan [id=22, name=M1, gender=male, phone=123456], LinkMan [id=23, name=M3, gender=null, phone=null]]
----------------------------
Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]
[LinkMan [id=22, name=M1, gender=male, phone=123456], LinkMan [id=23, name=M3, gender=null, phone=null]]
----------------------------
Customer [id=12, name=BBBBB, level=null, source=null, phone=null, mobile=null]
[LinkMan [id=21, name=M2, gender=female, phone=12345678]]
----------------------------

HQL左外连接查询 vs HQL迫切左外连接

• HQL左外连接语法：from Customer c left outer join c.linkMans
• HQL迫切左外连接语法：from Customer c left outer join fetch c.linkMans
• 左外连接查询返回的List集合中的元素是数组；迫切左外连接查询返回的List集合元素是对象

HQL右外连接查询

• 没有HQL迫切右外连接查询
• HQL右外连接查询语法：from Customer c right outer join c.linkMans

---

Hibernate检索策略

• Hibernate的检索策略分为两类：立即查询 vs 延迟查询
• 立即查询：根据id查询，调用get方法，一调用get方法立马发送SQL语句查询数据库
• 延迟查询：根据id查询，还有load方法，调用load方法不会马上发送SQL语句查询数据，只有得到对象里面的值的时候才会发送查询数据库的SQL语句

立即查询

延迟查询

• 延迟查询分为两类：
  （1） 类级别延迟查询：根据id查询返回实体类对象，调用load方法不会马上发送SQL语句
  （2） 关联界别延迟查询
  

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批量抓取

• 查询所有的客户，返回List集合，遍历List集合，得到每个客户，得到每个客户的所有联系人

@Test
public void testQuery18() {
	SessionFactory sessionFactory = HibernateUtils.getSessionFactory();
	Session session = sessionFactory.openSession();
	Transaction tx = session.beginTransaction();
	
	Query query = session.createQuery("from Customer");
	// 得到所有的客户
	List<Customer> customers = query.list();
	for (Customer customer : customers) {
		System.out.println(customer);
		Set<LinkMan> linkMans = customer.getLinkMans();
		for (LinkMan linkMan : linkMans) {
			System.out.println(linkMan);
		}
		System.out.println("-----------------------------------------");
	}
	
	tx.commit();
	session.close();
	sessionFactory.close();
}
------------------------------------------------------------------------------------
Hibernate: 
    select
        customer0_.id as id1_0_,
        customer0_.name as name2_0_,
        customer0_.level as level3_0_,
        customer0_.source as source4_0_,
        customer0_.phone as phone5_0_,
        customer0_.mobile as mobile6_0_ 
    from
        t_customer customer0_
Customer [id=11, name=AAAAA, level=Vip, source=??, phone=110, mobile=123456]
Hibernate: 
    select
        linkmans0_.fk_limlman_customer as fk_limlm5_1_0_,
        linkmans0_.id as id1_1_0_,
        linkmans0_.id as id1_1_1_,
        linkmans0_.name as name2_1_1_,
        linkmans0_.gender as gender3_1_1_,
        linkmans0_.phone as phone4_1_1_,
        linkmans0_.fk_limlman_customer as fk_limlm5_1_1_ 
    from
        t_linkman linkmans0_ 
    where
        linkmans0_.fk_limlman_customer=?
LinkMan [id=22, name=M1, gender=male, phone=123456]
LinkMan [id=23, name=M3, gender=null, phone=null]
-----------------------------------------
Customer [id=12, name=BBBBB, level=null, source=null, phone=null, mobile=null]
Hibernate: 
    select
        linkmans0_.fk_limlman_customer as fk_limlm5_1_0_,
        linkmans0_.id as id1_1_0_,
        linkmans0_.id as id1_1_1_,
        linkmans0_.name as name2_1_1_,
        linkmans0_.gender as gender3_1_1_,
        linkmans0_.phone as phone4_1_1_,
        linkmans0_.fk_limlman_customer as fk_limlm5_1_1_ 
    from
        t_linkman linkmans0_ 
    where
        linkmans0_.fk_limlman_customer=?
LinkMan [id=21, name=M2, gender=female, phone

• 楼上的代码会导致多次查询数据库
• 解决方案：在用户的映射配置文件中的set标签增加batch-size属性，该属性值越大，发送的SQL语句就越少