转载

Hibernate

下面过一遍 Hibernate

这个只大致过一遍

Hibernate 和Mybatis 都为ORM层框架

架构

配置对象

数据库连接：由 Hibernate 支持的一个或多个配置文件处理。这些文件是 hibernate.properties 和 hibernate.cfg.xml。

类映射设置：这个组件创造了 Java 类和数据库表格之间的联系。

SessionFactory 对象

配置对象用于创建 SessionFactory对象使用配置文件为应哟配置 Hibernate 实例化会话对象 SessionFactory 线程安全为应用程序所使用

Session 对象

与数据库的物理连接对象，session青量级的，非线程安全

Transaction 对象

数据库的事物

Query 对象

执行 hql查询

Criteria

对对象进行检索

搭建环境

选择maven进行下载

https://bintray.com/hibernate/artifacts/hibernate-orm

<dependency>
  <groupId>org.hibernate</groupId>
  <artifactId>hibernate-agroal</artifactId>
  <version>5.3.10.Final</version>
  <type>pom</type>
</dependency>

maven 填入 mysql 驱动

https://search.maven.org/artifact/mysql/mysql-connector-java/8.0.16/jar

<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>8.0.16</version>
</dependency>

配置

进行如下配置

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration SYSTEM
		"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
	<session-factory>
		<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
		<property name="hibernate.connection.driver_class">com.mysql.cj.jdbc.Driver</property>
		
		<!-- Assume test is the database name -->
		<property name="hibernate.connection.url">jdbc:mysql://47.94.95.84:3453/hibernate</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.connection.password">1111</property>
		
		<!-- List of XML mapping files -->
		<mapping resource="Employee.hbm.xml"/>
	
	</session-factory>
</hibernate-configuration>

目前目录结构如下

Hibernate

会话

会话三态

瞬时状态: 没有与session关联，数据库中没有相关记录

持久状态：对数据库表进行持久化保存

脱管状态：关闭会话，将会进入托管状态

持久化类

package com.ming.pojo;

/**
 * 新闻对象
 * @author ming
 */
public class News {
    // 新闻类属性
    private Integer id;
    // 新闻标题
    private String title;
    // 新闻内容
    private String content;

    public void setId(Integer id) {
        this.id = id;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public Integer getId() {
        return id;
    }

    public String getTitle() {
        return title;
    }

    public String getContent() {
        return content;
    }
}

映射文件

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
		"-//Hibernate/Hibernate Mapping DTD//EN"
		"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
	<class name="com.ming.pojo.Employee" table="EMPLOYEE">
		<meta attribute="class-description">
			This class contains the employee detail.
		</meta>
		<id name="id" type="int" column="id">
			<generator class="native"/>
		</id>
		<property name="firstName" column="first_name" type="string"/>
		<property name="lastName" column="last_name" type="string"/>
		<property name="salary" column="salary" type="int"/>
	</class>
</hibernate-mapping>

CRUD

package com.ming;


import com.ming.pojo.Employee;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;

import java.util.Iterator;
import java.util.List;

/**
 * @author ming
 */
public class ManageEmployee {
    private SessionFactory factory;

    public ManageEmployee(SessionFactory sessionFactory){
        factory = sessionFactory;
    }


    public Integer addEmployee(String fname, String lname, int salary){
        // 开启一个会话
        Session session = factory.openSession();
        // 事物
        Transaction tx = null;
        Integer employeeID = null;

        try{
            // 获得一个事物
            tx = session.beginTransaction();
            // 生成雇员对象
            Employee employee = new Employee(fname, lname, salary);
            // 进行保存操作 回填主键
            employeeID = (Integer) session.save(employee);
            // 提交事物
            tx.commit();
        }catch (HibernateException e) {
            if (tx!=null) tx.rollback();
            e.printStackTrace();
        }finally {
            session.close();
        }
        return employeeID;
    }
    /* Method to  READ all the employees */
    public void listEmployees( ){
        Session session = factory.openSession();
        Transaction tx = null;
        try{
            tx = session.beginTransaction();
            // 使用查询语句，，创建出一个查询 Query   来自于表Employee 返回列表
            List employees = session.createQuery("FROM Employee").list();
            // 进行迭代操作
            for (Iterator iterator =
                 employees.iterator(); iterator.hasNext();){
                Employee employee = (Employee) iterator.next();
                System.out.print("First Name: " + employee.getFirstName());
                System.out.print("  Last Name: " + employee.getLastName());
                System.out.println("  Salary: " + employee.getSalary());
            }
            // 提交事物
            tx.commit();
        }catch (HibernateException e) {
            if (tx!=null) tx.rollback();
            e.printStackTrace();
        }finally {
            session.close();
        }
    }
    /* Method to UPDATE salary for an employee */
    public void updateEmployee(Integer EmployeeID, int salary ){
        Session session = factory.openSession();
        Transaction tx = null;
        try{
            tx = session.beginTransaction();
            // 根据class获得一个雇员对象  此时进入持久态
            Employee employee =
                    (Employee)session.get(Employee.class, EmployeeID);
            // 进行设置  此时为持久态，数据库会进行保存操作
            employee.setSalary( salary );
            // 进行更新 写入数据库
            session.update(employee);
            // 提交事物以后，将会关闭会话， 进入托管状态
            tx.commit();
        }catch (HibernateException e) {
            if (tx!=null) tx.rollback();
            e.printStackTrace();
        }finally {
            session.close();
        }
    }
    /* Method to DELETE an employee from the records */
    public void deleteEmployee(Integer EmployeeID){
        Session session = factory.openSession();
        Transaction tx = null;
        try{
            tx = session.beginTransaction();
            Employee employee =
                    (Employee)session.get(Employee.class, EmployeeID);
            session.delete(employee);
            tx.commit();
        }catch (HibernateException e) {
            if (tx!=null) tx.rollback();
            e.printStackTrace();
        }finally {
            session.close();
        }
    }
}

<%@ page import="org.hibernate.cfg.Configuration" %>
<%@ page import="com.ming.ManageEmployee" %>
<html>
<body>
<h2>Hello World!</h2>

<%
    ManageEmployee manageEmployee = null;
    try{
        manageEmployee = new ManageEmployee(new Configuration().configure().buildSessionFactory());
    }catch (Throwable ex) {
        System.err.println("Failed to create sessionFactory object." + ex);
        throw new ExceptionInInitializerError(ex);
    }
    ManageEmployee ME = manageEmployee;

    /* Add few employee records in database */
    Integer empID1 = ME.addEmployee("Zara", "Ali", 1000);
    Integer empID2 = ME.addEmployee("Daisy", "Das", 5000);
    Integer empID3 = ME.addEmployee("John", "Paul", 10000);

    /* List down all the employees */
    ME.listEmployees();

    /* Update employee's records */
    ME.updateEmployee(empID1, 5000);

    /* Delete an employee from the database */
    ME.deleteEmployee(empID2);

    /* List down new list of the employees */
    ME.listEmployees();
%>
</body>
</html>