Hibernate学习笔记
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目录
官网：Hibernate 中文文档 | Hibernate 中文网
主流 ORM 框架 Object Relation Mapping 对象关系映射，将⾯向对象映射成⾯向关系。
如何使⽤
1、导⼊相关依赖
2、创建 Hibernate 配置⽂件
3、创建实体类
4、创建实体类-关系映射⽂件
5、调⽤ Hibernate API 完成操作
1.一对一关系
具体操作
1、创建 Maven ⼯程，pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<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/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.example</groupId>
<artifactId>hibernateDemo</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.49</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.5.8.Final</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.10</version>
</dependency>
</dependencies>
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.xml</include>
</includes>
</resource>
</resources>
</build>
</project>2、hibernate.cfg.xml
构建 SessionFactory ⾮常耗费资源，所以通常⼀个⼯程只需要创建⼀个 SessionFactory。
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- 数据源配置 -->
<property name="connection.username">root</property>
<property name="connection.password">root</property>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=false</property>
<!-- C3P0 -->
<property name="hibernate.c3p0.acquire_increment">10</property>
<property name="hibernate.c3p0.idle_test_period">10000</property>
<property name="hibernate.c3p0.timeout">5000</property>
<property name="hibernate.c3p0.max_size">30</property>
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_statements">10</property>
<!-- 数据库⽅⾔ -->
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<!-- 打印SQL -->
<property name="show_sql">true</property>
<!-- 格式化SQL -->
<property name="format_sql">true</property>
<!-- 是否⾃动⽣成数据库 -->
<property name="hibernate.hbm2ddl.auto"></property>
<!-- 注册实体关系映射⽂件 -->
<mapping resource="com/newer/xxh/People.hbm.xml"></mapping>
<mapping resource="com/newer/xxh/Customer.hbm.xml"></mapping>
<mapping resource="com/newer/xxh/Orders.hbm.xml"></mapping>
<mapping resource="com/newer/xxh/Account.hbm.xml"></mapping>
<mapping resource="com/newer/xxh/Course.hbm.xml"></mapping>
</session-factory>
</hibernate-configuration>
3、创建实体类
package com.newer.xxh;
import lombok.Data;
@Data
public class People {
private Integer id;
private String name;
private Double money;
}
4、创建实体关系映射⽂件
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.newer.xxh.People" table="people" dynamic-insert="true" dynamic-update="true" >
<id name="id" type="java.lang.Integer">
<column name="id"></column>
<generator class="identity"></generator>
</id>
<property name="name" type="java.lang.String">
<column name="name"></column>
</property>
<property name="money" type="java.lang.Double">
<column name="money"></column>
</property>
</class>
</hibernate-mapping>5、实体关系映射⽂件注册到 Hibernate 的配置⽂件中。
<!-- 注册实体关系映射⽂件 -->
<mapping resource="com/newer/xxh/People.hbm.xml"></mapping>6、使⽤ Hibernate API 完成数据操作。
import com.newer.xxh.*;
import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;
import org.hibernate.query.Query;
import java.util.Iterator;
import java.util.List;
public class Test {
public static void main(String[] args) {
Configuration configuration = new Configuration().configure();
Session session = configuration.buildSessionFactory().openSession();
People people = new People();
people.setName("马哥");
people.setMoney(200.2);
session.save(people);
session.beginTransaction().commit();
session.close();
}
}
以上就是最简单的一对一的。如果出现路径问题，可以考虑
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.xml</include>
</includes>
</resource>
</resources>
</build>2.一对多关系
客户和订单：
每个客户可以购买多个产品，⽣成多个订单，但是⼀个订单只能属于⼀个客户，所以客户 是⼀，订单是多。
customer表
orders表
Customer
package com.newer.xxh;
import lombok.Data;
import java.util.Set;
@Data
public class Customer {
private Integer id;
private String name;
private Set<Orders> orders;
}
Customer.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.newer.xxh.Customer" table="customer" >
<id name="id" type="java.lang.Integer">
<column name="id"></column>
<generator class="identity"></generator>
</id>
<property name="name" type="java.lang.String">
<column name="name"></column>
</property>
<set name="orders" table="orders" inverse="true" cascade="delete">
<key column="cid"></key>
<one-to-many class="com.newer.xxh.Orders"></one-to-many>
</set>
</class>
</hibernate-mapping>
- set 标签来配置实体类中的集合属性 orders
- name 实体类属性名
- table 表名
- key 外键
- one-to-many 与集合泛型的实体类对应
Orders
package com.newer.xxh;
import lombok.Data;
@Data
public class Orders {
private Integer id;
private String name;
private Customer customer;
}
Orders.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.newer.xxh.Orders" table="orders">
<id name="id" type="java.lang.Integer">
<column name="id"></column>
<generator class="identity"></generator>
</id>
<property name="name" type="java.lang.String">
<column name="name"></column>
</property>
<many-to-one name="customer" class="com.newer.xxh.Customer" column="cid"></many-to-one>
</class>
</hibernate-mapping>
- many-to-one 配置实体类对应的对象属性
- name 属性名
- class 属性对应的类column 外键
<!-- 注册实体关系映射⽂件 -->
<mapping resource="com/newer/xxh/Customer.hbm.xml"></mapping>
<mapping resource="com/newer/xxh/Orders.hbm.xml"></mapping>import com.newer.xxh.*;
import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;
import org.hibernate.query.Query;
import java.util.Iterator;
import java.util.List;
public class Test {
public static void main(String[] args) {
Configuration configuration = new Configuration().configure();
Session session = configuration.buildSessionFactory().openSession();
//创建 Customer
Customer customer = new Customer();
customer.setName("张三");
//创建 Orders
Orders orders = new Orders();
orders.setName("订单1");
//建⽴关联关系
orders.setCustomer(customer);
//保存
session.save(customer);
session.save(orders);
session.beginTransaction().commit();
session.close();
}
}
3.多对多关系
学⽣选课：⼀⻔课程可以被多个学⽣选择，⼀个学⽣可以选择多⻔课程，学⽣是多，课程也是多。
数据库中是通过两个⼀对多关系来维护的，学⽣和课程都是主表，额外增加⼀张中间表作为从表，两张主表和中间表都是⼀对多关系。
account表
course表
account_course表
Account
package com.newer.xxh;
import lombok.Data;
import java.util.Set;
@Data
public class Account {
private Integer id;
private String name;
private Set<Course> courses;
}
Account.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.newer.xxh.Account" table="account">
<id name="id" type="java.lang.Integer">
<column name="id"></column>
<generator class="identity"></generator>
</id>
<property name="name" type="java.lang.String">
<column name="name"></column>
</property>
<set name="courses" table="account_course">
<key column="cid"></key>
<many-to-many class="com.newer.xxh.Course" column="aid"></many-to-many>
</set>
</class>
</hibernate-mapping>
Course
package com.newer.xxh;
import lombok.Data;
import java.util.Set;
@Data
public class Course {
private Integer id;
private String name;
private Set<Account> accounts;
}
Course.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.newer.xxh.Course" table="course">
<id name="id" type="java.lang.Integer">
<column name="id"></column>
<generator class="identity"></generator>
</id>
<property name="name" type="java.lang.String">
<column name="name"></column>
</property>
<set name="accounts" table="account_course">
<key column="aid"></key>
<many-to-many class="com.newer.xxh.Account" column="cid"></many-to-many>
</set>
</class>
</hibernate-mapping>
<!-- 注册实体关系映射⽂件 -->
<mapping resource="com/newer/xxh/Account.hbm.xml"></mapping>
<mapping resource="com/newer/xxh/Course.hbm.xml"></mapping>import com.newer.xxh.*;
import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;
import java.util.HashSet;
import java.util.Set;
public class Test {
public static void main(String[] args) {
Configuration configuration = new Configuration().configure();
Session session = configuration.buildSessionFactory().openSession();
Course course = new Course();
course.setName("python");
Account account = new Account();
account.setName("李四");
Set<Course> courses = new HashSet<>();
courses.add(course);
account.setCourses(courses);
session.save(course);
session.save(account);
session.beginTransaction().commit();
session.close();
}
}
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