Hibernate 再接触 HQL
Category.java
package com.bjsxt.hibernate; import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id; @Entity
public class Category {
private int id;
private String name;
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
Topic.java
package com.bjsxt.hibernate; import java.util.Date; import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne; @Entity
public class Topic {
private int id;
private String title;
private Category category;
//private Category category2; private Date createDate; public Date getCreateDate() {
return createDate;
}
public void setCreateDate(Date createDate) {
this.createDate = createDate;
}
@ManyToOne(fetch=FetchType.LAZY)
public Category getCategory() {
return category;
}
public void setCategory(Category category) {
this.category = category;
}
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
} }
Msg
package com.bjsxt.hibernate; import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne; @Entity
public class Msg {
private int id;
private String cont;
private Topic topic;
@ManyToOne
public Topic getTopic() {
return topic;
}
public void setTopic(Topic topic) {
this.topic = topic;
}
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
} public String getCont() {
return cont;
}
public void setCont(String cont) {
this.cont = cont;
} }
Msginfo
package com.bjsxt.hibernate; import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne; public class MsgInfo { //VO DTO Value Object username p1 p2 UserInfo->User->DB
private int id;
private String cont;
private String topicName;
private String categoryName;
public MsgInfo(int id, String cont, String topicName, String categoryName) {
super();
this.id = id;
this.cont = cont;
this.topicName = topicName;
this.categoryName = categoryName;
}
public String getTopicName() {
return topicName;
}
public void setTopicName(String topicName) {
this.topicName = topicName;
}
public String getCategoryName() {
return categoryName;
}
public void setCategoryName(String categoryName) {
this.categoryName = categoryName;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
} public String getCont() {
return cont;
}
public void setCont(String cont) {
this.cont = cont;
} }
Test
test1
@Test
public void testHQL_01() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Category"); //ql语言
List<Category> categories = (List<Category>)q.list(); //取出对象
for(Category c : categories) {
System.out.println(c.getName());
}
session.getTransaction().commit();
session.close(); }
@Test
public void testHQL_02() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Category c where c.name > 'c5'"); //是对象而不是表名字
List<Category> categories = (List<Category>)q.list(); //返回一个对象数组
for(Category c : categories) {
System.out.println(c.getName());
}
session.getTransaction().commit();
session.close();
}
@Test
public void testHQL_03() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Category c order by c.name desc"); //逆序
List<Category> categories = (List<Category>)q.list(); //返回对象数组
for(Category c : categories) {
System.out.println(c.getName());
}
session.getTransaction().commit();
session.close();
}
@Test
public void testHQL_04() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("select distinct c from Category c order by c.name desc"); //没有重复的主键
List<Category> categories = (List<Category>)q.list();
for(Category c : categories) {
System.out.println(c.getName());
}
session.getTransaction().commit();
session.close();
}
@Test
public void testHQL_05() {
Session session = sf.openSession();
session.beginTransaction();
/*Query q = session.createQuery("from Category c where c.id > :min and c.id < :max"); //:相当于占位符
//q.setParameter("min", 2); //设置min值
//q.setParameter("max", 8); //设置max值，也可以用下面这种设法
q.setInteger("min", 2);
q.setInteger("max", 8);*/
Query q = session.createQuery("from Category c where c.id > :min and c.id < :max")
.setInteger("min", 2)
.setInteger("max", 8);
List<Category> categories = (List<Category>)q.list();
for(Category c : categories) {
System.out.println(c.getId() + "-" + c.getName());
}
session.getTransaction().commit();
session.close();
}
@Test
public void testHQL_06() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Category c where c.id > ? and c.id < ?"); //另外一种设法
q.setParameter(0, 2)
.setParameter(1, 8);
// q.setParameter(1, 8);
List<Category> categories = (List<Category>)q.list();
for(Category c : categories) {
System.out.println(c.getId() + "-" + c.getName());
}
session.getTransaction().commit();
session.close();
}
//分页
@Test
public void testHQL_07() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Category c order by c.name desc");
q.setMaxResults(4); //设置每页的
q.setFirstResult(2); //设置起始
List<Category> categories = (List<Category>)q.list();
for(Category c : categories) {
System.out.println(c.getId() + "-" + c.getName());
}
session.getTransaction().commit();
session.close();
}
@Test
public void testHQL_08() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("select c.id, c.name from Category c order by c.name desc");
List<Object[]> categories = (List<Object[]>)q.list();
for(Object[] o : categories) {
System.out.println(o[0] + "-" + o[1]);
}
session.getTransaction().commit();
session.close();
}
//设定fetch type 为lazy后将不会有第二条sql语句
@Test
public void testHQL_09() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Topic t where t.category.id = 1");
List<Topic> topics = (List<Topic>)q.list();
for(Topic t : topics) {
System.out.println(t.getTitle());
//System.out.println(t.getCategory().getName());
}
session.getTransaction().commit();
session.close();
}
//设定fetch type 为lazy后将不会有第二条sql语句
@Test
public void testHQL_10() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Topic t where t.category.id = 1");
List<Topic> topics = (List<Topic>)q.list();
for(Topic t : topics) {
System.out.println(t.getTitle());
}
session.getTransaction().commit();
session.close();
}
@Test
public void testHQL_11() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Msg m where m.topic.category.id = 1"); //导航 因为有多对一的关系
for(Object o : q.list()) {
Msg m = (Msg)o;
System.out.println(m.getCont());
}
session.getTransaction().commit();
session.close();
}
//了解即可
//VO Value Object
//DTO data transfer object
@Test
public void testHQL_12() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("select new com.bjsxt.hibernate.MsgInfo(m.id, m.cont, m.topic.title, m.topic.category.name) from Msg");
for(Object o : q.list()) {
MsgInfo m = (MsgInfo)o;
System.out.println(m.getCont());
}
session.getTransaction().commit();
session.close();
}
//动手测试left right join
//为什么不能直接写Category名，而必须写t.category
//因为有可能存在多个成员变量（同一个类），需要指明用哪一个成员变量的连接条件来做连接
@Test
public void testHQL_13() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("select t.title, c.name from Topic t join t.category c "); //join Category c
for(Object o : q.list()) {
Object[] m = (Object[])o;
System.out.println(m[0] + "-" + m[1]);
}
session.getTransaction().commit();
session.close();
}
//学习使用uniqueResult
@Test
public void testHQL_14() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Msg m where m = :MsgToSearch "); //不重要
Msg m = new Msg();
m.setId(1);
q.setParameter("MsgToSearch", m);
Msg mResult = (Msg)q.uniqueResult(); /返回唯一的一个
System.out.println(mResult.getCont());
session.getTransaction().commit();
session.close();
}
@Test
public void testHQL_15() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("select count(*) from Msg m"); //返回数量
long count = (Long)q.uniqueResult();
System.out.println(count);
session.getTransaction().commit();
session.close();
}
@Test
public void testHQL_16() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("select max(m.id), min(m.id), avg(m.id), sum(m.id) from Msg m");
Object[] o = (Object[])q.uniqueResult();
System.out.println(o[0] + "-" + o[1] + "-" + o[2] + "-" + o[3]);
session.getTransaction().commit();
session.close();
}
@Test
public void testHQL_17() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Msg m where m.id between 3 and 5");
for(Object o : q.list()) {
Msg m = (Msg)o;
System.out.println(m.getId() + "-" + m.getCont());
}
session.getTransaction().commit();
session.close();
}
@Test
public void testHQL_18() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Msg m where m.id in (3,4, 5)");
for(Object o : q.list()) {
Msg m = (Msg)o;
System.out.println(m.getId() + "-" + m.getCont());
}
session.getTransaction().commit();
session.close();
}
//is null 与 is not null
@Test
public void testHQL_19() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Msg m where m.cont is not null");
for(Object o : q.list()) {
Msg m = (Msg)o;
System.out.println(m.getId() + "-" + m.getCont());
}
session.getTransaction().commit();
session.close();
}
pART2
更改Topic
package com.bjsxt.hibernate; import java.util.ArrayList;
import java.util.Date;
import java.util.List; import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany; @Entity
@NamedQueries(
{
@NamedQuery(name="topic.selectCertainTopic", query="from Topic t where t.id = :id")
}
)
/*
@NamedNativeQueries(
{
@NamedNativeQuery(name="topic.select2_5Topic", query="select * from topic limit 2, 5")
}
)
*/ public class Topic {
private int id;
private String title;
private Category category;
private Date createDate;
private List<Msg> msgs = new ArrayList<Msg>();
@OneToMany(mappedBy="topic")
public List<Msg> getMsgs() { return msgs;
}
public void setMsgs(List<Msg> msgs) {
this.msgs = msgs;
}
public Date getCreateDate() {
return createDate;
}
public void setCreateDate(Date createDate) {
this.createDate = createDate;
}
@ManyToOne(fetch=FetchType.LAZY)
public Category getCategory() {
return category;
}
public void setCategory(Category category) {
this.category = category;
}
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
} }
@Test
public void testHQL_20() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Topic t where t.msgs is empty"); for(Object o : q.list()) {
Topic t = (Topic)o;
System.out.println(t.getId() + "-" + t.getTitle());
}
session.getTransaction().commit();
session.close(); } @Test
public void testHQL_21() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Topic t where t.title like '%5'"); for(Object o : q.list()) {
Topic t = (Topic)o;
System.out.println(t.getId() + "-" + t.getTitle());
}
session.getTransaction().commit();
session.close(); } @Test
public void testHQL_22() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Topic t where t.title like '_5'"); for(Object o : q.list()) {
Topic t = (Topic)o;
System.out.println(t.getId() + "-" + t.getTitle());
}
session.getTransaction().commit();
session.close(); }
//不重要
@Test
public void testHQL_23() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("select lower(t.title)," +
"upper(t.title)," +
"trim(t.title)," +
"concat(t.title, '***')," +
"length(t.title)" +
" from Topic t "); for(Object o : q.list()) {
Object[] arr = (Object[])o;
System.out.println(arr[] + "-" + arr[] + "-" + arr[] + "-" + arr[] + "-" + arr[] + "-");
}
session.getTransaction().commit();
session.close(); } @Test
public void testHQL_24() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("select abs(t.id)," +
"sqrt(t.id)," +
"mod(t.id, 2)" +
" from Topic t "); for(Object o : q.list()) {
Object[] arr = (Object[])o;
System.out.println(arr[] + "-" + arr[] + "-" + arr[] );
}
session.getTransaction().commit();
session.close(); } @Test
public void testHQL_25() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("select current_date, current_time, current_timestamp, t.id from Topic t"); for(Object o : q.list()) {
Object[] arr = (Object[])o;
System.out.println(arr[] + " | " + arr[] + " | " + arr[] + " | " + arr[]);
}
session.getTransaction().commit();
session.close(); } @Test
public void testHQL_26() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Topic t where t.createDate < :date");
q.setParameter("date", new Date());
for(Object o : q.list()) {
Topic t = (Topic)o;
System.out.println(t.getTitle());
}
session.getTransaction().commit();
session.close(); } @Test
public void testHQL_27() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("select t.title, count(*) from Topic t group by t.title") ;
for(Object o : q.list()) {
Object[] arr = (Object[])o;
System.out.println(arr[] + "|" + arr[]);
}
session.getTransaction().commit();
session.close(); } @Test
public void testHQL_28() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("select t.title, count(*) from Topic t group by t.title having count(*) >= 1") ;
for(Object o : q.list()) {
Object[] arr = (Object[])o;
System.out.println(arr[] + "|" + arr[]);
}
session.getTransaction().commit();
session.close(); } @Test
public void testHQL_29() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Topic t where t.id < (select avg(t.id) from Topic t)") ;
for(Object o : q.list()) {
Topic t = (Topic)o;
System.out.println(t.getTitle());
}
session.getTransaction().commit();
session.close(); } @Test
public void testHQL_30() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("from Topic t where t.id < ALL (select t.id from Topic t where mod(t.id, 2)= 0) ") ;
for(Object o : q.list()) {
Topic t = (Topic)o;
System.out.println(t.getTitle());
}
session.getTransaction().commit();
session.close(); } //用in 可以实现exists的功能
//但是exists执行效率高
@Test
public void testHQL_31() {
Session session = sf.openSession();
session.beginTransaction();// t.id not in (1)
Query q = session.createQuery("from Topic t where not exists (select m.id from Msg m where m.topic.id=t.id)") ;
// Query q = session.createQuery("from Topic t where exists (select m.id from Msg m where m.topic.id=t.id)") ;
for(Object o : q.list()) {
Topic t = (Topic)o;
System.out.println(t.getTitle());
}
session.getTransaction().commit();
session.close(); } //update and delete
//规范并没有说明是不是要更新persistent object，所以如果要使用，建议在单独的trasaction中执行 @Test
public void testHQL_32() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.createQuery("update Topic t set t.title = upper(t.title)") ; q.executeUpdate();
q = session.createQuery("from Topic");
for(Object o : q.list()) {
Topic t = (Topic)o;
System.out.println(t.getTitle());
}
session.createQuery("update Topic t set t.title = lower(t.title)")
.executeUpdate();
session.getTransaction().commit();
session.close(); } //不重要
@Test
public void testHQL_33() {
Session session = sf.openSession();
session.beginTransaction();
Query q = session.getNamedQuery("topic.selectCertainTopic");
q.setParameter("id", );
Topic t = (Topic)q.uniqueResult();
System.out.println(t.getTitle());
session.getTransaction().commit();
session.close(); } //Native（了解）
@Test
public void testHQL_34() {
Session session = sf.openSession();
session.beginTransaction();
SQLQuery q = session.createSQLQuery("select * from category limit 2,4").addEntity(Category.class);
List<Category> categories = (List<Category>)q.list();
for(Category c : categories) {
System.out.println(c.getName());
}
session.getTransaction().commit();
session.close(); } @Test
public void testHQL_35() {
//尚未实现JPA命名的NativeSQL }
QBC
@Test
public void testQBC() {
Session session = sf.openSession();
session.beginTransaction();
//criterion 标准/准则/约束
Criteria c = session.createCriteria(Topic.class) //from Topic .add(Restrictions.gt("id", )) //greater than = id > 2
.add(Restrictions.lt("id", )) //little than = id < 8
.add(Restrictions.like("title", "t_"))
.createCriteria("category")
.add(Restrictions.between("id", , )) //category.id >= 3 and category.id <=5
;
//DetachedCriterea
for(Object o : c.list()) {
Topic t = (Topic)o;
System.out.println(t.getId() + "-" + t.getTitle());
}
session.getTransaction().commit();
session.close(); }
QBE
@Test
public void testSave() {
Session session = sf.openSession();
session.beginTransaction(); for(int i=; i<; i++) {
Category c = new Category();
c.setName("c" + i);
session.save(c);
} for(int i=; i<; i++) {
Category c = new Category();
c.setId();
Topic t = new Topic();
t.setCategory(c);
t.setTitle("t" + i);
t.setCreateDate(new Date());
session.save(t); } for(int i=; i<; i++) { Topic t = new Topic();
t.setId();
Msg m = new Msg();
m.setCont("m" + i);
m.setTopic(t);
session.save(m); } session.getTransaction().commit();
session.close();
} //is empty and is not empty
//query by criteria query by example
@Test
public void testQBE() {
Session session = sf.openSession();
session.beginTransaction();
Topic tExample = new Topic();
tExample.setTitle("T_"); Example e = Example.create(tExample)
.ignoreCase().enableLike();
Criteria c = session.createCriteria(Topic.class)
.add(Restrictions.gt("id", ))
.add(Restrictions.lt("id", ))
.add(e)
; for(Object o : c.list()) {
Topic t = (Topic)o;
System.out.println(t.getId() + "-" + t.getTitle());
}
session.getTransaction().commit();
session.close(); }
Hibernate 再接触 HQL的更多相关文章
- Hibernate 再接触 基础配置 搭建Log4j环境 Junit日志环境等
<!-- Drop and re-create the database schema on startup --> <property name="hbm2ddl.aut ...
- Hibernate 再接触 CRUD
1.save 一对多双向 package com.bjsxt.hibernate; import java.util.HashSet; import java.util.Set; import jav ...
- Hibernate 再接触 核心开发接口
1.可以重载方法进行配置文件的指定 sessionFactory = new AnnotationConfiguration().configure("hibernate.xml" ...
- Hibernate 再接触 悲观锁和乐观锁
为什么取1248 二进制 CRUD 移位效率高 在并发和效率选择一个平衡点 一般不会考虑幻读 因为我们不会再一个事务里查询两次,(只能设置为seralizable) 悲观锁和乐观锁的前提是read-u ...
- Hibernate 再接触 一级缓存 二级缓存 查询缓存
缓存 就是把本来应该放在硬盘里的东西放在内存里 将来存内存里读 一级缓存: session缓存 二级缓存: sessionFactory级别的 (适合经常访问,数据量有限,改动不大) 很多的se ...
- Hibernate 再接触 性能优化
Sessionclear 否则session缓存里越来越多 Java有内存泄露吗? 在语法中没有(垃圾自动回收) 但是在实际中会有 比如读文件没有关什么的 1+N问题 解决方法:把fetch设置为la ...
- Hibernate 再接触 ID生成策略
Xml 方法 在student.hbm.xml中 <generator class="uuid"></generator> 取值如下 1.identity: ...
- Hibernate 再接触 树状结构设计以及学生课程成绩表的设计
1 树状结构的设计 package com.bjsxt.hibernate; import java.util.HashSet; import java.util.Set; import javax. ...
- Hibernate 再接触 继承映射
用一张 每一个类一张表 建立外键 第一种 一张总表 Person package com.bjsxt.hibernate; import javax.persistence.Discriminator ...
随机推荐
- Javascript中的this指向。
一.JavaScript中的函数 在了解this指向之前,要先弄明白函数执行时它的执行环境是如何创建的,这样可以更清楚的去理解JavaScript中的this指向. function fn(x,y,n ...
- 弹性布局（Flex布局）整理
一. 弹性布局 一个好的网站都有让用户看上去很舒服的布局,一个网站的布局也会或多或少影响到它的浏览量,看完阮大神的博客,就想把弹性布局整理一下. 在平时的我们常用的布局类型有以下几种: 1.浮动+定 ...
- C#中关于对out和ref的认识
1.两者都是按照地址进行传递的.2.ref关键字是的参数按照引用传递的方式进行.他的效果是控制权传递会调用方法是,可以对这个参数进行修改 要使用ref参数,那么方法的定义和调用方法都必须进行显示的 ...
- JAVA常用设计模式(一、单例模式、工厂模式)
JAVA设计模式之单例模式 import java.util.HashMap; import java.util.Map; /** * 设计模式之单例模式 * 单例模式(Singleton Patte ...
- Git版本库创建（包含文件权限设置 Linux环境下）
确保git服务已安装成功,如果没有安装git服务查看:Git源码安装 Linux指定安装目录 1.创建git用户,并设置密码.并禁止git用户通过shell登录服务器(注意如果需要安装gitolite ...
- 阿里java开发规范 强制约束
http://news.51cto.com/art/201901/591018.htm :阿里开发强制要求的11条索引创建规范,提高性能 https://blog.csdn.net/Lujunwei ...
- 运行gunicorn失败：[ERROR] Connection in use: ('0.0.0.0', 8000)
参考:https://pdf-lib.org/Home/Details/5262 执行命令:gunicorn -w 4 -b 0.0.0.0:8000 wsgi:app,遇到如下错误: [2019-0 ...
- 第一个Python小项目：图片转换成字符图片
实现的效果: ...
- 黄聪：xampp运行MySQL shutdown unexpectedly解决方案
相信不少喜欢WordPress的朋友和我一样,会用xampp在本地搭建一个网站学习调试,但是在用的过程中也会遇到些麻烦,毕竟我们都是小白,今天就分享一个xampp运行MySQL数据时出现 Error: ...
- Flask--(一对多demo)作者书籍模型
一对多模型的增加和删除 后端实现: from flask import Flask from flask import flash from flask import redirect from fl ...