Hibernate的基本使用

Hibernate 的基本使用

数据表定义如下：

create table employee(
    employee_id integer,
    name        text,
    salary      numeric,
);

如下图，建立 Maven 项目工程

resources 资源文件夹下创建 hibernate.cfg.xml 的 Hibernate 配置文件

创建 Employee.hbm.xml 的 Hibernate 映射文件

创建 POJO 类 Employee 为 Employee.hbm.xml 的映射类

添加 Maven 依赖如下

<dependencies>
    <!-- hibernate-->
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-agroal</artifactId>
        <version>5.5.8.Final</version>
        <type>pom</type>
    </dependency>

    <!-- postgresql数据库驱动-->
    <dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
        <version>42.2.24.jre7</version>
    </dependency>
</dependencies>

hibernate.cfg.xml 配置文件如下

<?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>
        <!--数据库驱动(这里以PostgreSQL为例)-->
        <property name="hibernate.connection.driver_class">org.postgresql.Driver</property>
        <property name="hibernate.dialect">org.hibernate.dialect.PostgreSQL95Dialect</property>
        <!-- 数据库配置-->
        <property name="hibernate.connection.url">jdbc:postgresql://localhost:5432/emp_database</property>
        <property name="hibernate.connection.username">postgres</property>
        <property name="hibernate.connection.password">postgres</property>
        <property name="hibernate.show_sql">true</property>
        <!-- 数据库映射文件-->
        <mapping resource="cn/zzq/hibernate/demo/Employee.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

Employee.hbm.xml 映射文件如下

<?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 package="cn.zzq.hibernate.demo">
    <class name="cn.zzq.hibernate.demo.Employee" table="public.employee" catalog="web">
        <id name="employeeId" column="employee_id">
            <generator class="assigned"/>
        </id>

        <property name="name" column="name" length="128"/>
        <property name="salary" column="salary" length="128"/>
    </class>
</hibernate-mapping>

employee 表对应的 POJO 类定义如下

package cn.zzq.hibernate.demo;
public class Employee {

    private int employeeId;
    private String name;
    private float salary;


    public Employee(int employeeId, String name, float salary) {
        this.employeeId = employeeId;
        this.name = name;
        this.salary = salary;
    }

    public Employee() {

    }

    public int getEmployeeId() {
        return employeeId;
    }

    public void setEmployeeId(int employeeId) {
        this.employeeId = employeeId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public float getSalary() {
        return salary;
    }

    public void setSalary(float salary) {
        this.salary = salary;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "employeeId=" + employeeId +
                ", name='" + name + '\'' +
                ", salary=" + salary +
                '}';
    }
}

主测试类 Hibernate.java 定义如下

package cn.zzq.hibernate.demo;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.query.Query;

public class Hibernate {
    public static void main(String[] args) {
        try {
            // 配置Hibernate
            Configuration configuration = new Configuration();
            configuration.configure("hibernate.cfg.xml");

            // 创建session(与数据库连接的会话)
            StandardServiceRegistry standardServiceRegistry = new StandardServiceRegistryBuilder().configure().build();
            SessionFactory sessionFactory = configuration.buildSessionFactory(standardServiceRegistry);
            Session session = sessionFactory.openSession();

            // 开启事务
            Transaction transaction = session.beginTransaction();

            // 保存到数据库
            session.save(new Employee(1,"Tom12",4000f));
            session.save(new Employee(2,"Tom23",7000f));
            session.save(new Employee(3,"Tom23",8000f));

            // HQL查询
            Query q = session.createQuery("from Employee employee WHERE employee.salary>5000.0");

            System.out.println(q.list());

            // 提交事务
            transaction.commit();

            // 关闭session
            session.close();
            sessionFactory.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

输出结果如上图所示