Hibernate笔记一（Hibernate简单配置和操作）

ゝ一世哀愁。 2024-02-17 22:11 67阅读 0赞

#### Hibernate ####

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1.什么是Hibernate？

*  Hibernate是一个ORM(Object/Relationship Mapping)框架，即对象关系映射。就是将对象中的属性和数据库中的字段通过映射的关系一一对应起来。它的设计目标是将软件开发人员从大量相同的数据持久层相关编程工作中解放出来。无论是从设计草案还是从一个遗留数据库开始，开发人员都可以采用Hibernate。Hibernate不仅负责从Java类到数据库表的映射（还包括从Java数据类型到SQL数据类型的映射），还提供了面向对象的数据查询检索机制，从而极大地缩短的手动处理SQL和JDBC上的开发时间。  
    
    
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2.Hibernate配置

*  Hibernate核心配置文件  
    官方推荐将Hibernate核心配置文件命名为**hibernate.cfg.xml**，直接放到项目的src目录之下。核心配置文件配置如下：

<?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>
            
            <property name="connection.username">root</property>
            
            <property name="connection.password">root</property>
            
            <property name="connection.url">jdbc:mysql:///hibernate?characterEncoding=utf-8</property>
            
            <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
            
            <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
            
            <property name="show_sql">true</property>
            
            <property name="format_sql">true</property>
            
            <property name="hbm2ddl.auto">update</property>
    
            
            <mapping resource="com/walter/vo/Student.hbm.xml"/>
        </session-factory>
    </hibernate-configuration>

*  实体类：在使用Hibernate时，实体类推荐的定义方法是：  
    
    
     *  1.属性私有化；
     *  2.显现定义出无参构造
     *  3.要有标准的getter和setter方法

public class Student {
        
    
        private int id;
        private int age;
        private String name;
        private String address;
        private Date birthday;
        public Student() {
            super();
            // TODO Auto-generated constructor stub
        }
        public Student(int age, String name, String address, Date birthday) {
            super();
            this.age = age;
            this.name = name;
            this.address = address;
            this.birthday = birthday;
        }
    
        public Student(int id, int age, String name, String address, Date birthday) {
            super();
            this.id = id;
            this.age = age;
            this.name = name;
            this.address = address;
            this.birthday = birthday;
        }
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public int getAge() {
            return age;
        }
        public void setAge(int age) {
            this.age = age;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getAddress() {
            return address;
        }
        public void setAddress(String address) {
            this.address = address;
        }
        public Date getBirthday() {
            return birthday;
        }
        public void setBirthday(Date birthday) {
            this.birthday = birthday;
        }   
    }

*  实体类的映射文件：实体类的映射文件命名格式推荐是**Person.hbm.xml**，即 实体类的类名+.hbm+.xml

<?xml version="1.0"?>
    <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
    
    
    <hibernate-mapping>
        
        <class name="com.walter.vo.Student" table="STUDENT">
            
            <id name="id" type="int" >
                <column name="ID" />
                <generator class="native" />
            </id>
            <property name="age" type="int">
                <column name="AGE" />
            </property>
            
            <property name="name" type="java.lang.String" not-null="true">
                <column name="NAME" />
            </property>
            <property name="address" type="java.lang.String">
                <column name="ADDRESS" />
            </property>
            
            <property name="birthday" type="date">
                <column name="BIRTHDAY" />
            </property>
        </class>
    </hibernate-mapping>

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3.Hibernate的简单使用

*  定义工具类

public class HibernateUtil {
        
    
        private static SessionFactory sessionFactory;
        static {
            Configuration configuration = new Configuration();
            // 加载Hibernate核心配置文件并解析
            configuration.configure();
            //获取session工厂对象
            sessionFactory = configuration.buildSessionFactory();
        }
        /**
         * 获取工厂对象
         * @return
         */
        public static SessionFactory getSessionFactory() {
            return sessionFactory;
        }
        /**
         * 获取session对象
         * @return
         */
        public static Session getSession() {
            return sessionFactory.openSession();
        }
        /**
         * 关闭session对象
         * @param s
         */
        public static void close(Session s) {
            if (s != null)
                s.close();
        }

*  测试

public class StudentTest {
        
    
        private Session session;
        private Transaction transaction;
    
        /**
         * 创建session对象，开启事务
         */
        @Before
        public void init() {
            session = HibernateUtil.getSession();
            transaction = session.beginTransaction();
        }
        /**
         * 提交事务，关闭session对象
         */
        @After
        public void distroy() {
            transaction.commit();
            HibernateUtil.close(session);
        }
        /**
         * 添加学生
         */
        @Test
        public void testSaveStudent() {
            Student student = new Student(10, "李四", "北京", new Date());
            session.save(student);
    
        }
        /**
         * 查询所有学生信息
         */
        @Test
        public void testQueryAll(){
            List<Student> students = session.createQuery("from Student").list();
            System.out.println(students);
        }
        /**
         * 根据id查询学生信息
         */
        @Test
        public void testQueryById(){
            System.out.println(session.get(Student.class, 1));
        }
        /**
         * 根据id修改学生信息
         */
        @Test
        public void testUpdate(){
            Student student = new Student(1,10, "王五", "上海", new Date());
            session.update(student);
        }
        @Test
        /**
         * 根据id删除学生信息
         */
        public void testDelById(){
            Student student = new Student(2);
            session.delete(student);
        }
    }

从测试的情况我们可以看出，Hibernate使我们的开发不用再书写繁琐的sql语句，而是针对对象进行编程。从这也可以看出Hibernate确实减轻了我们开发人员不少工作量。以上只是对Hibernate基本的介绍和操作。针对Hibernate对表与表之间的关联在以后的笔记中进行讲解。