Hibernate入门

最新推荐文章于 2022-07-21 15:25:14 发布

邂逅于晚风

最新推荐文章于 2022-07-21 15:25:14 发布

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文章标签： hibernate maven java

本文链接：https://blog.youkuaiyun.com/weixin_58670730/article/details/120809868

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1.Hibernate是什么

Hibernate 是持久层的ORM框架。Hibernate对JDBC进行了封装，也就是说，我们可以使用Hibernate来完成原来我们使用JDBC完成的操作，也就是与数据库的交互操作。

2.什么是ORM

Object Relation Mapping（对象关系映射），所谓的ORM就是利用描述对象和数据库表之间映射的元数据，自动把Java应用程序中的对象，持久化到关系型数据库的表中。通过操作Java对象，就可以完成对数据库表的操作。可以把ORM理解为关系型数据和对象的一个纽带，开发人员只需要关注纽带一端映射的对象即可。从而提高数据访问层的编程效率。

3.Hibernate主键生成策略

generator元素：表示了一个主键生成器，它用来为持久化类实例生成唯一的标识。

3.1程序员自己控制：assigned

3.2 数据库控制: identity(标识列/自动增长) sequence

3.3 hibernate控制:increment uuid/uuid.hex

3.4 其它:native

4.Hibernate使用

4.1添加hibernate jar包依赖

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.wyy</groupId>
  <artifactId>Maven_hib</artifactId>
  <packaging>war</packaging>
  <version>0.0.1-SNAPSHOT</version>
  <name>Maven_hib Maven Webapp</name>
  <url>http://maven.apache.org</url>
  <properties>
		<junit.version>4.12</junit.version>
		<servlet.version>4.0.0</servlet.version>
		<hibernate.version>5.3.0.Final</hibernate.version>
		<mysql.driver.version>8.0.19</mysql.driver.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>${junit.version}</version>
			<scope>test</scope>
		</dependency>

		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>javax.servlet-api</artifactId>
			<version>${servlet.version}</version>
			<scope>provided</scope>
		</dependency>

		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-core</artifactId>
			<version>${hibernate.version}</version>
		</dependency>

		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>${mysql.driver.version}</version>
		</dependency>
	</dependencies>
  <build>
    <finalName>Maven_hib</finalName>
  </build>
</project>

4.2添加hibernate.cfg.xml配置文件

引入hibernate-configuration-3.0.dtd约束

注意：引入的mysql依赖版本保持一致

<?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>
		<!-- 1. 数据库相关 -->
<!-- 		<property name="connection.username">root</property> -->
<!-- 		<property name="connection.password">123456</property> -->
<!-- 		<property name="connection.url">jdbc:mysql://47.100.191.44:3308/lx?useUnicode=true&amp;characterEncoding=UTF-8</property> -->
<!-- 		<property name="connection.driver_class">com.mysql.jdbc.Driver</property> -->
		<property name="connection.username">root</property>
		<property name="connection.password">123456</property>
		<property name="connection.url">jdbc:mysql://127.0.0.1:3306/wyy?useUnicode=true&amp;characterEncoding=utf8&amp;serverTimezone=GMT&amp;useSSL=true</property>
		<property name="connection.driver_class">com.mysql.cj.jdbc.Driver</property>
		<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
		<!-- <property name="dialect">org.hibernate.dialect.Oracle10gDialect</property> -->

		<!-- 配置本地事务（No CurrentSessionContext configured!） -->
		<property name="hibernate.current_session_context_class">thread</property>

		<!-- 2. 调试相关 -->
		<property name="show_sql">true</property>
		<property name="format_sql">true</property>
		<!-- 配置映射文件 -->
		<mapping resource="com/wyy/entity/user.hbm.xml" />

		<!-- 主键生成策略 -->
<!-- 		<mapping resource="com/zking/two/entity/Student.hbm.xml" /> -->
<!-- 		<mapping resource="com/zking/two/entity/Worker.hbm.xml" /> -->

		<!-- 一对多 -->
<!-- 		<mapping resource="com/zking/four/entity/Order.hbm.xml" /> -->
<!-- 		<mapping resource="com/zking/four/entity/OrderItem.hbm.xml" /> -->
		<!-- 一对多的自关联 -->
<!-- 		<mapping resource="com/zking/five/entity/TreeNode.hbm.xml" /> -->

		<!-- 多对多 -->
<!-- 		<mapping resource="com/zking/five/entity/Category.hbm.xml" /> -->
<!-- 		<mapping resource="com/zking/five/entity/Book.hbm.xml" /> -->
	</session-factory>
</hibernate-configuration>

4.3添加实体类映射文件

引入hibernate-mapping-3.0.dtd约束

<?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>
        <!-- name  对象属性
		 type  属性类别
		 column 表列段
		 generator 主键生成格式
	  -->
	<class name="com.wyy.entity.User" table="t_hibernate_user">
		<id name="id" type="java.lang.Integer" column="id">
			<generator class="assigned" />
		</id>
		<property name="userName" type="java.lang.String" column="user_name">
		</property>
		<property name="userPwd" type="java.lang.String" column="user_pwd">
		</property>
		<property name="realName" type="java.lang.String" column="real_name">
		</property>
		<property name="sex" type="java.lang.String" column="sex">
		</property>
		<property name="birthday" type="java.sql.Date" column="birthday">
		</property>
		<property insert="false" update="false" name="createDatetime"
			type="java.sql.Timestamp" column="create_datetime">
		</property>
		<property name="remark" type="java.lang.String" column="remark">
		</property>
	</class>

</hibernate-mapping>

<generator class="assigned" />

主键由自己控制

4.4实体类（User）

package com.wyy.entity;

import java.sql.Date;
import java.sql.Timestamp;

public class User {
	private int id;
	private String userName;
	private String userPwd;
	private String realName;
	private String sex;
	private Date birthday;
	private Timestamp createDatetime;
	private String remark;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getUserName() {
		return userName;
	}
	public void setUserName(String userName) {
		this.userName = userName;
	}
	public String getUserPwd() {
		return userPwd;
	}
	public void setUserPwd(String userPwd) {
		this.userPwd = userPwd;
	}
	public String getRealName() {
		return realName;
	}
	public void setRealName(String realName) {
		this.realName = realName;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public Date getBirthday() {
		return birthday;
	}
	public void setBirthday(Date birthday) {
		this.birthday = birthday;
	}
	public Timestamp getCreateDatetime() {
		return createDatetime;
	}
	public void setCreateDatetime(Timestamp createDatetime) {
		this.createDatetime = createDatetime;
	}
	public String getRemark() {
		return remark;
	}
	public void setRemark(String remark) {
		this.remark = remark;
	}
	@Override
	public String toString() {
		return "User [id=" + id + ", userName=" + userName + ", userPwd=" + userPwd + ", realName=" + realName
				+ ", sex=" + sex + ", birthday=" + birthday + ", createDatetime=" + createDatetime + ", remark="
				+ remark + "]";
	}
	
	
	
}

5.Hibernate 之CRUD

5.1删除

通过id获取对应数据，然后提交修改

创建对象，给ID赋值，然后提交修改

	//1.对框架核心配置文件进行建模
		Configuration configure = new Configuration().configure("/hibernate.cfg.xml");
		//2.获取sessionFactory工厂
		SessionFactory buildSessionFactory = configure.buildSessionFactory();
		 //3.获取session会话
		Session openSession = buildSessionFactory.openSession();
		//4.开启事务（查询不需要事务）
		Transaction beginTransaction = openSession.beginTransaction();
		//5.session 操作对象
		User user = openSession.get(User.class, 12);//查找对应数据
		openSession.delete(user);
//		User user = new User();
//		user.setId(12);
//		openSession.delete(user);
		// 6.提交事务（查询不需要事务）
		beginTransaction.commit();
		//7.关闭session
		openSession.close();

5.2修改

通过id获取对应数据，然后提交修改

创建对象，给对象赋值，然后提交修改

//1.对框架核心配置文件进行建模
	Configuration configure = new Configuration().configure("/hibernate.cfg.xml");
	//2.获取sessionFactory工厂
	SessionFactory buildSessionFactory = configure.buildSessionFactory();
	 //3.获取session会话
	Session openSession = buildSessionFactory.openSession();
	//4.开启事务（查询不需要事务）
	Transaction beginTransaction = openSession.beginTransaction();
	//5.session 操作对象
	User user = openSession.get(User.class, 14);
	user.setUserName("cc");
	openSession.update(user);
	// 6.提交事务（查询不需要事务）
	beginTransaction.commit();
	//7.关闭session
	openSession.close();

5.3增加

//1.对框架核心配置文件进行建模
	Configuration configure = new Configuration().configure("/hibernate.cfg.xml");
	//2.获取sessionFactory工厂
	SessionFactory buildSessionFactory = configure.buildSessionFactory();
	 //3.获取session会话
	Session openSession = buildSessionFactory.openSession();
	//4.开启事务（查询不需要事务）
	Transaction beginTransaction = openSession.beginTransaction();
	//5.session 操作对象
	User user=new User();
	user.setId(34);
	user.setBirthday(new Date(System.currentTimeMillis()));
	user.setUserName("执念");
	openSession.save(user);
	// 6.提交事务（查询不需要事务）
	beginTransaction.commit();
	//7.关闭session
	openSession.close();

5.4查询

5.4.1简单查询

//1.对框架核心配置文件进行建模
			Configuration configure = new Configuration().configure("/hibernate.cfg.xml");
			//2.获取sessionFactory工厂
			SessionFactory buildSessionFactory = configure.buildSessionFactory();
			 //3.获取session会话
			Session openSession = buildSessionFactory.openSession();
			//4.session 操作对象
			List list = openSession.createQuery("  from User  ").list();
			for (Object object : list) {
				System.out.println(object);
			}
			//7.关闭session
			openSession.close();

5.4.2聚合函数

//1.对框架核心配置文件进行建模
			Configuration configure = new Configuration().configure("/hibernate.cfg.xml");
			//2.获取sessionFactory工厂
			SessionFactory buildSessionFactory = configure.buildSessionFactory();
			 //3.获取session会话
			Session openSession = buildSessionFactory.openSession();
			//4.session 操作对象
			List list = openSession.createQuery(" select COUNT(1) from User where userName like '%z%' ").list();
			for (Object object : list) {
				System.out.println(object);
			}
			//7.关闭session
			openSession.close();

5.4.3分页模糊查询

/**
	 * 通用查询
	 * @param path 配置文件
	 * @param hql  执行语句
	 * @param p  分页工具
	 */
	public void executeQuery(String path,String hql,PageBean p) {
		//1.对框架核心配置文件进行建模
		Configuration configure = new Configuration().configure(path);
		//2.获取sessionFactory工厂
		SessionFactory buildSessionFactory = configure.buildSessionFactory();
		 //3.获取session会话
		Session session = buildSessionFactory.openSession();
		//计算数据总条数hql
		Query createQuery = session.createQuery(getcount(hql));
		//将总条数赋值给PageBean的total
		p.setTotal(createQuery.getSingleResult().toString());
		//执行hql
		Query createQuery2 = session.createQuery(hql);
		//设置起始下标
		createQuery2.setFirstResult(p.getStartIndex());
		//设置最大每页条数
	  	createQuery2.setMaxResults(p.getRows());
	  	List list = createQuery2.list();
		for (Object object : list) {
			System.out.println(object);
		}
		session.close();
	}
	private String getcount(String hql) {
		//考虑用户传过来的hql可能大小不同
		 String upperCase = hql.toUpperCase();
//		 System.out.println(upperCase);
		return "select count(*) "+hql.substring(upperCase.indexOf("FROM"));
	}

调用

PageBean p = new PageBean();
		//设置每页条数
		p.setRows(2);
		new BaseDemo().executeQuery("/hibernate.cfg.xml", " from User where userName like '%z%'  ", p);

5.4.4操作原生SQL查询

SQL 是操作数据库表 , HQL 操作对象

//1.对框架核心配置文件进行建模
			Configuration configure = new Configuration().configure("/hibernate.cfg.xml");
			//2.获取sessionFactory工厂
			SessionFactory buildSessionFactory = configure.buildSessionFactory();
			 //3.获取session会话
			Session openSession = buildSessionFactory.openSession();
//			//4.session 操作对象
			/* 原生SQL */
            List list = openSession.createSQLQuery("select * from t_hibernate_user where user_name like '%z%' ").addEntity(User.class).list();
			/* HQL */
        // List list = openSession.createQuery(" select COUNT(1) from User where userName like '%z%' ").list();
			for (Object object : list) {
				System.out.println(object);
			}
//			//7.关闭session
			openSession.close();