Hibernate ORM框架——项目一：Hibernate查询；项目二：集合相关查询
MySQL数据库-------------------------------------------------- use demo; select * from CLASSINFO; select * from persons; delete from CLASSINFO; delete from persons; insert into CLASSINFO values('c111','banji1'); insert into CLASSINFO values('c222','banji2'); insert into persons values('p1','p111','c111') insert into persons values('p2','p222','c111') insert into persons values('p3','p333','c222') insert into persons values('p4','p444','c222') insert into persons values('p5','p555',null) select pid,name from persons order by pid desc;--降序 select pid,name from persons order by pid asc;--升序 select COUNT(*),name from persons group by name select (select pid,name from persons),p.rci from persons p left join CLASSINFO c on p.rci=c.cid group by p.rci; //查询------------------------------------------------------ 1.hibernate整体上的查询分为3类 （1）HQL（Hibernate Query Languange） 面相对象的查询语言，所以跨数据库 （2）Native SQL（本地sql，原生的某个特定的数据的sql） （3）critiria（规则） （4）命名查询（Named Query） 2.从行数来区分，hibernate提供了 （1）list方法：多行 （2）uniqueResult：单行 的查询方式 3.Hql语句的大小写问题 （1）hql里面的实体，实体的属性是区分大小写的 eg:from Person(实体名); （2） 其它的不区分 eg：from Person(实体名) where name（属性名）="";即where后面的 4. 关于查询需要涉及的知识点 （1） 排序， （2）过滤， （3）分组， （4）聚合函数， （5）列数的控制（select name，age） 注意点： （1）查询语句中加别名的规范： Person [as] p 选取所有列，直接写p （2）不能直接在查询列里面写上做关联的字段 因为它一般牵涉到多表的查询处理 总结上午学习知识点： 1.查询所有 2.过滤条件 （1）写死 （2）？ （3）： 3.排序（升序，降序） 4.聚合函数 5.分组 6.list方法和uniqueResult方法 -------子查询，链接查询----- ------native sql------- ---规则（criteria）
项目一：
（1）配置文件不变
（2）HibernateUtil不变
（3.1）班级实体
private String cid ; private String name; //一对多 private Set<Person> persons;
（3.2）学生实体
private String pid ;//UUID private String name; private ClassInfo ci;
//多对一
（4）两个实体映射文件和上一篇一样（双向多对一，一对多）
（5）Main测试
package com.nf; import java.util.List; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.query.Query; import shuang.m2oo2m.ClassInfo; import shuang.m2oo2m.Person; import util.HibernateUtil; public class Main { public static void main(String[] args) { /*在List中使用，泛型object[]与泛型实体类的区别 * 由于实体类重写了toString方法， * 所以select p from Person p中的p与实体的字段与属性名一样 * 所以可以直接使用泛型实体类遍历 * * 而如果查询语句的*，是p.name,p.pid之类的，只有两列，与实体中的有三个属性不匹配， * 所以需要使用泛型object[]遍历 * */ //String hql="select p from Person p"; //queryAll(); //过滤条件：？参数 //wenhaoParam(); //过滤条件:命名参数 //NameParam(); //排序（升序，降序） //paixu(); //聚合函数、分组 //groupBy(); groupByCid(); } public static void queryAll() { SessionFactory sf = HibernateUtil.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); /*String hql="select p from Person p";*/ String hql="from Person"; Query q = s.createQuery(hql); List<Person> list = q.list(); System.out.println(list.size());//5 for(Person data : list){ //System.out.println(data.getName()); /*结果 * 5 p111 p222 p333 p444 p555 * */ //System.out.println(data); /*结果 * 5 Person [pid=p1, name=p111] Person [pid=p2, name=p222] Person [pid=p3, name=p333] Person [pid=p4, name=p444] Person [pid=p5, name=p555] * */ System.out.println(data+"_____and_____"+data.getCi()); /*结果： * Person [pid=p1, name=p111]_____and_____ClassInfo [cid=c111, name=banji1] Person [pid=p2, name=p222]_____and_____ClassInfo [cid=c111, name=banji1] Person [pid=p3, name=p333]_____and_____ClassInfo [cid=c222, name=banji2] Person [pid=p4, name=p444]_____and_____ClassInfo [cid=c222, name=banji2] Person [pid=p5, name=p555]_____and_____null * */ } tx.commit(); s.close(); sf.close(); } public static void wenhaoParam() { SessionFactory sf = HibernateUtil.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); //String hql = "select new list(p.pid,p.name) from Person as p "; //转换格式list(p.pid,p.name)的话，则需要用object遍历，否则直接用Person实体遍历 String hql = "select p.name,p.pid from Person as p where rci =?"; Query q = s.createQuery(hql); ClassInfo cls = new ClassInfo(); cls.setCid("c222"); q.setParameter(0, cls);//?的设值 List<Object[]> list = q.list(); //System.out.println(list.get(0)); //[Ljava.lang.Object;@25c5e994 for (Object[] objects : list) { System.out.println(objects[0]); System.out.println(objects[1]); } /*结果: * p111 p1*/ tx.commit(); s.close(); sf.close(); } public static void NameParam() { SessionFactory sf = HibernateUtil.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); //查询实体的所有记录 String hql = "select p.name,p.pid from Person as p where name =:myname"; Query q = s.createQuery(hql); q.setParameter("myname", "p111");//：命名参数 List<Object[]> list = q.list(); for(Object[] data : list){ System.out.println(data[0]); System.out.println(data[1]); } /*结果: * p111 p1*/ tx.commit(); s.close(); sf.close(); } public static void paixu() { SessionFactory sf= HibernateUtil.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); //String hql="select pid,name from Person order by pid asc";//升序 String hql="select p.pid,p.name from Person p order by pid desc";//降序 Query q = s.createQuery(hql); List<Object[]> list = q.list(); for (Object[] object : list) { System.out.println(object[0]); System.out.println(object[1]); } tx.commit(); s.close(); } public static void groupBy() { SessionFactory sf = HibernateUtil.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); //String hql = "select COUNT(name),name from Person group by name "; String hql = "select COUNT(*),name from Person group by name "; Query q = s.createQuery(hql); List<Object[]> list = q.list(); for (Object[] objects : list) { System.out.println(objects[0]); System.out.println(objects[1]); } tx.commit(); s.close(); } }
项目二：（集合相关）
返回类型 a）返回实体集合List<Person> b)返回Object[]集合List<Object[]> c)返回Map集合List<Map> new map d)返回List的集合List<List> new list e)返回自定义类型集合List<定制类型> new PersonInfo(renid,renmingzi,banji) PersonInfo -------子查询，链接查询----- ------native sql------- ---规则（criteria）
Main测试
package com.nf; import java.util.ArrayList; import java.util.List; import java.util.Map; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.query.Query; import shuang.m2oo2m.Person; import shuang.m2oo2m.PersonInfo; import util.HibernateUtil; public class Main { public static void main(String[] args) { //queryAll(); //List集合中放着map集合 //returnListMap(); //List集合里放-自定义类型 //returnCustomClass(); //in范围 //inQuery(); inQuery2(); } private static void template() { SessionFactory sf = HibernateUtil.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); tx.commit(); s.close(); sf.close(); } private static void queryAll() { SessionFactory sf = HibernateUtil.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); //String hql = "from Person"; String hql = "select p from Person p"; Query q = s.createQuery(hql); List<Person> list = q.list(); for(Person p: list){ System.out.println(p); } tx.commit(); s.close(); sf.close(); } private static void returnListMap() { SessionFactory sf = HibernateUtil.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); /*String hql = "select new map(p.pid,p.name) from Person p"; Query q = s.createQuery(hql); List<Map> list = q.list(); for(Map p: list){ System.out.println(p.get("0"));//默认pid的别名为0 System.out.println(p.get("1"));//默认name的别名为1 }*/ String hql = "select new map(p.pid as bianhao,p.name as mingzi) from Person p"; Query q = s.createQuery(hql); List<Map> list = q.list(); for(Map p: list){ System.out.println(p.get("bianhao")); System.out.println(p.get("mingzi")); } tx.commit(); s.close(); sf.close(); } private static void returnCustomClass() { SessionFactory sf = HibernateUtil.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); String hql = "select new shuang.m2oo2m.PersonInfo(p.pid,p.name) from Person p"; Query q = s.createQuery(hql); List<PersonInfo> list = q.list(); for(PersonInfo p: list){ System.out.println(p); } tx.commit(); s.close(); sf.close(); } private static void inQuery() { SessionFactory sf = HibernateUtil.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); String hql = "select p from Person p where p.name in ('p111','p333')"; Query q = s.createQuery(hql); List<Person> list = q.list(); for(Person p: list){ System.out.println(p); } tx.commit(); s.close(); sf.close(); } private static void inQuery2() { SessionFactory sf = HibernateUtil.getSessionFactory(); Session s = sf.openSession(); Transaction tx = s.beginTransaction(); String hql = "select p from Person p where p.name in :names"; Query q = s.createQuery(hql); List<String> allnames = new ArrayList<>(); allnames.add("p111"); allnames.add("p444"); q.setParameter("names", allnames); List<Person> list = q.list(); for(Person p: list){ System.out.println(p); } tx.commit(); s.close(); sf.close(); } }
//List集合里放-自定义类型：相关的类
PersonInfo类
package shuang.m2oo2m; public class PersonInfo { private String xx; private String yy; public PersonInfo(){ } public PersonInfo(String aa,String bb){ this.xx = aa; this.yy = bb; } public String getXx() { return xx; } public void setXx(String xx) { this.xx = xx; } public String getYy() { return yy; } public void setYy(String yy) { this.yy = yy; } @Override public String toString() { return "PersonInfo [xx=" + xx + ", yy=" + yy + "]"; } }
/*以上个人整理笔记，如果有误或者有不懂的地方，欢迎评论与指出*/
