HQL语句中不可以出现与表有关的内容,而是对象的属性
实体类(注意配置文件):
package domain; import java.util.HashSet; import java.util.Set; //客户实体 public class Customer { private Long cust_id; private String cust_name; private String cust_source; private String cust_industry; private String cust_level; private String cust_linkman; private String cust_phone; private String cust_mobile; //使用set集合,表达一对多关系 private Set<LinkMan> linkMens = new HashSet<LinkMan>(); public Set<LinkMan> getLinkMens() { return linkMens; } public void setLinkMens(Set<LinkMan> linkMens) { this.linkMens = linkMens; } public Long getCust_id() { return cust_id; } public void setCust_id(Long cust_id) { this.cust_id = cust_id; } public String getCust_name() { return cust_name; } public void setCust_name(String cust_name) { this.cust_name = cust_name; } public String getCust_source() { return cust_source; } public void setCust_source(String cust_source) { this.cust_source = cust_source; } public String getCust_industry() { return cust_industry; } public void setCust_industry(String cust_industry) { this.cust_industry = cust_industry; } public String getCust_level() { return cust_level; } public void setCust_level(String cust_level) { this.cust_level = cust_level; } public String getCust_linkman() { return cust_linkman; } public void setCust_linkman(String cust_linkman) { this.cust_linkman = cust_linkman; } public String getCust_phone() { return cust_phone; } public void setCust_phone(String cust_phone) { this.cust_phone = cust_phone; } public String getCust_mobile() { return cust_mobile; } public void setCust_mobile(String cust_mobile) { this.cust_mobile = cust_mobile; } @Override public String toString() { return "Customer [cust_id=" + cust_id + ", cust_name=" + cust_name + "]"; } }
抽取工具类:
package utils; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; public class HibernateUtils { private static SessionFactory sf; static{ //1 创建,调用空参构造 Configuration conf = new Configuration().configure(); //2 根据配置信息,创建 SessionFactory对象 sf = conf.buildSessionFactory(); } //获得session => 获得全新session public static Session openSession(){ //3 获得session Session session = sf.openSession(); return session; } //获得session => 获得与线程绑定的session public static Session getCurrentSession(){ //3 获得session Session session = sf.getCurrentSession(); return session; } }
测试类:
基本语法:
package hql; import java.util.List; import org.hibernate.Query; import org.hibernate.Session; import org.hibernate.Transaction; import org.junit.Test; import domain.Customer; import utils.HibernateUtils; //学习HQL语法 public class Demo { //基本语法 @Test public void fun1(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql = " from domain.Customer ";//完整写法 String hql2 = " from Customer "; //简单写法 String hql3 = " from java.lang.Object "; //查询所有Object对象,即所有对象 Query query = session.createQuery(hql); List list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //排序 public void fun2(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql1 = " from domain.Customer order by cust_id asc ";//完整写法升序 String hql2 = " from domain.Customer order by cust_id desc ";//完整写法降序 Query query = session.createQuery(hql2); List list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //条件查询 public void fun3(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql1 = " from domain.Customer where cust_id =? ";//?按所有传值 String hql2 = " from domain.Customer where cust_id = :id ";//:按名称传值 Query query = session.createQuery(hql2); //query.setParameter(0, 5l); query.setParameter("id", 5l); List list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //分页查询 public void fun4(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql1 = " from domain.Customer ";//完整写法 Query query = session.createQuery(hql1); //类似SQL中的limit ?,? // (当前页数-1)*每页条数 query.setFirstResult(0); query.setMaxResults(2); List list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //统计查询 //count 计数 //sum 求和 //avg 平均数 //max //min public void fun5(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql1 = " select count(*) from domain.Customer "; String hql2 = " select sum(cust_id) from domain.Customer "; String hql3 = " select avg(cust_id) from domain.Customer "; String hql4 = " select max(cust_id) from domain.Customer "; String hql5 = " select min(cust_id) from domain.Customer "; Query query = session.createQuery(hql3); Number number = (Number) query.uniqueResult(); System.out.println(number); //---------------------------------------------------- tx.commit(); session.close(); } @Test //投影查询 //查询对象某一个属性 public void fun6(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql1 = " select cust_name from domain.Customer "; String hql2 = " select cust_name,cust_id from domain.Customer "; String hql3 = " select new Customer(cust_id,cust_name) from domain.Customer "; //如果实体类有相应构造方法,也可以执行 Query query = session.createQuery(hql2); List list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } }
多表查询:
再创建一个实体类:
package domain; //联系人实体 public class LinkMan { private Long lkm_id; private Character lkm_gender; private String lkm_name; private String lkm_phone; private String lkm_email; private String lkm_qq; private String lkm_mobile; private String lkm_memo; private String lkm_position; // 表达多对一关系 private Customer customer; public Customer getCustomer() { return customer; } public void setCustomer(Customer customer) { this.customer = customer; } public Long getLkm_id() { return lkm_id; } public void setLkm_id(Long lkm_id) { this.lkm_id = lkm_id; } public Character getLkm_gender() { return lkm_gender; } public void setLkm_gender(Character lkm_gender) { this.lkm_gender = lkm_gender; } public String getLkm_name() { return lkm_name; } public void setLkm_name(String lkm_name) { this.lkm_name = lkm_name; } public String getLkm_phone() { return lkm_phone; } public void setLkm_phone(String lkm_phone) { this.lkm_phone = lkm_phone; } public String getLkm_email() { return lkm_email; } public void setLkm_email(String lkm_email) { this.lkm_email = lkm_email; } public String getLkm_qq() { return lkm_qq; } public void setLkm_qq(String lkm_qq) { this.lkm_qq = lkm_qq; } public String getLkm_mobile() { return lkm_mobile; } public void setLkm_mobile(String lkm_mobile) { this.lkm_mobile = lkm_mobile; } public String getLkm_memo() { return lkm_memo; } public void setLkm_memo(String lkm_memo) { this.lkm_memo = lkm_memo; } public String getLkm_position() { return lkm_position; } public void setLkm_position(String lkm_position) { this.lkm_position = lkm_position; } }
测试类:
package hql; import java.util.Arrays; import java.util.List; import org.hibernate.Query; import org.hibernate.Session; import org.hibernate.Transaction; import org.junit.Test; import domain.Customer; import utils.HibernateUtils; //学习HQL语法(不常用) - 多表查询语法 public class Demo2 { //原生SQL中: // 交叉连接-笛卡尔积(避免) // select * from A,B // 内连接 // |-隐式内连接 // select * from A,B where b.aid = a.id // |-显式内连接 // select * from A inner join B on b.aid = a.id // 外连接 // |- 左外 // select * from A left [outer] join B on b.aid = a.id // |- 右外 // select * from A right [outer] join B on b.aid = a.id //--------------------------------------------------------------------- //HQL的多表查询 //内连接(迫切) //外连接 // |-左外(迫切) // |-右外(迫切) @Test //HQL 内连接 => 将连接的两端对象分别返回.放到数组中. public void fun1(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql = " from Customer c inner join c.linkMens "; //c相当于别名 Query query = session.createQuery(hql); List<Object[]> list = query.list(); for(Object[] arr : list){ System.out.println(Arrays.toString(arr)); } //---------------------------------------------------- tx.commit(); session.close(); } @Test //HQL 迫切内连接 => 帮我们进行封装.返回值就是一个对象 public void fun2(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql = " from Customer c inner join fetch c.linkMens "; Query query = session.createQuery(hql); List<Customer> list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //HQL 左外连接 => 将连接的两端对象分别返回.放到数组中. public void fun3(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql = " from Customer c left join c.linkMens "; Query query = session.createQuery(hql); List<Object[]> list = query.list(); for(Object[] arr : list){ System.out.println(Arrays.toString(arr)); } //---------------------------------------------------- tx.commit(); session.close(); } @Test //HQL 右外连接 => 将连接的两端对象分别返回.放到数组中. public void fun4(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql = " from Customer c right join c.linkMens "; Query query = session.createQuery(hql); List<Object[]> list = query.list(); for(Object[] arr : list){ System.out.println(Arrays.toString(arr)); } //---------------------------------------------------- tx.commit(); session.close(); } }
补上内连接与外连接区别: