Hibernate---对象的三种状态

<?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 元素用于配置Hibernate中的属性 ???????????键:值 ???????--> ???????<!-- hibernate.connection.driver_class : 连接数据库的驱动 ?--> ???????<property name="hibernate.connection.driver_class"> ???????????com.mysql.jdbc.Driver ???????</property> ???????<!-- hibernate.connection.username : 连接数据库的用户名 --> ???????<property name="hibernate.connection.username">root</property> ???????<!-- hibernate.connection.password : 连接数据库的密码 --> ???????<property name="hibernate.connection.password">root</property> ???????<!-- hibernate.connection.url : 连接数据库的地址,路径 --> ???????<property name="hibernate.connection.url"> ???????????jdbc:mysql://localhost:3306/Hibernate ???????</property> ???????<!-- show_sql: 操作数据库时,会 向控制台打印sql语句 --> ???????<property name="show_sql">true</property> ???????<!-- format_sql: 打印sql语句前,会将sql语句先格式化 ?--> ???????<property name="format_sql">true</property> ???????<!-- hbm2ddl.auto: 生成表结构的策略配置 ???????????update(最常用的取值): 如果当前数据库中不存在表结构,那么自动创建表结构. ???????????如果存在表结构,并且表结构与实体一致,那么不做修改 ???????????如果存在表结构,并且表结构与实体不一致,那么会修改表结构.会保留原有列. ???????????create(很少):无论是否存在表结构.每次启动Hibernate都会重新创建表结构.(数据会丢失) ???????????create-drop(极少): 无论是否存在表结构.每次启动Hibernate都会重新创建表结构.每次Hibernate运行结束时,删除表结构. ???????????validate(很少):不会自动创建表结构.也不会自动维护表结构.Hibernate只校验表结构. 如果表结构不一致将会抛出异常. ???????--> ???????<property name="hbm2ddl.auto">update</property> ???????<!-- 数据库方言配置 ???????????org.hibernate.dialect.MySQLDialect (选择最短的) ???????--> ???????<property name="hibernate.dialect"> ???????????org.hibernate.dialect.MySQLDialect ???????</property> ???????<!-- hibernate.connection.autocommit: 事务自动提交 ???????????<property name="hibernate.connection.autocommit">true</property> ???????--> ???????<!-- 将Session与线程绑定=> 只有配置了该配置,才能使用getCurrentSession --> ???????<property name="hibernate.current_session_context_class"> ???????????thread ???????</property> ???????<!-- 引入ORM 映射文件 ???????????填写src之后的路径 ???????--> ???????<mapping resource="resource/User.hbm.xml"/> ???</session-factory></hibernate-configuration>

<?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"><!-- ORM元数据 ?表对象关系映射文件 ???package : 配置该配置文件中类所在的包. ?--><hibernate-mapping package="com.huhu.domain"> ???<!-- class: 配置实体与表的关系 ???????name : 填写实体的完整类名 ???????table: 与实体对应表的名称 ???????dynamic-insert:动态插入 默认值是false ???????????????????????true=>如果字段值为null,不参与insert语句 ????????dynamic-update:动态更新 ?默认值"false" ????????????????????????true=> 没改动过的属性,将不会生成到update语句中 ????--> ???<class name="com.huhu.domain.User" table="t_user"> ???????<!-- id: 配置实体与表中 id对应 ???????????name: user对象中标识主键的属性名称 ???????????column: 主键在表中的列名 ???????????length: 列的数据长度 ???????????unsaved-value(不常用): 指定主键为什么值时,当做null来处理. ??????????access(强烈推荐不要用):field 那么在操作属性时,会直接操作对应的字段而不是get/set方法 ????????--> ???????<id name="id" column="id"> ???????????<!-- generator:主键生成策略 ????????????????????1.increment ?数据库自己生成主键. 先从数据库中查询最大的ID值,将ID值加1作为新的主键 ???????????????????2.identity ?依赖于数据的主键自增功能 ???????????????????3.sequence序列,依赖于数据中的序列功能(Oracle). ???????????????????4.hilo(纯了解,永远用不到) : Hibernate自己实现序列的算法,自己生成主键. (hilo算法 ) ???????????????????5.native 自动根据数据库判断,三选一. identity|sequence|hilo ???????????????????6.uuid ?生成32位的不重复随机字符串当做主键 ???????????????????7.assigned 自己指定主键值. 表的主键是自然主键时使用. ????????????--> ???????????<generator class="native"></generator> ???????</id> ???????<!-- property : 实体中属性与表中列的对应 ????????????name : 实体中属性名称 ????????????column : 表中列的名称 ????????????length : 数据长度 ????????????precision: 小数点后的精度 ????????????scale:有效位数 ????????????insert(一般不用): 该属性是否加入insert语句. ????????????update(一般不用): 该属性是否加入update语句. ????????????not-null : 指定属性的约束是否使用 非空 ????????????unique : 指定属性的约束是否使用 唯一 ????????--> ???????<!-- ???????????type: 表达该属性的类型 ???????????可以用三种方式指定属性 ???????????java类型 ?数据库类型指定Hibernate类型指定 ???????????java.lang.Stringvarcharstring ????????--> ???????<property name="name" column="name"></property> ???????<property name="password" column="password"></property> ???</class></hibernate-mapping>

package com.huhu.domain;// Hibernatepublic class User { ???private Integer id; ???private String name; ???private String password; ???public Integer getId() { ???????return id; ???} ???public void setId(Integer id) { ???????this.id = id; ???} ???public String getName() { ???????return name; ???} ???public void setName(String name) { ???????this.name = name; ???} ???public String getPassword() { ???????return password; ???} ???public void setPassword(String password) { ???????this.password = password; ???} ???@Override ???public String toString() { ???????return "User [id=" + id + ", name=" + name + ", password=" + password ???????????????+ "]"; ???}}

package com.huhu.utils;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.hibernate.classic.Session;//完成Hibernate工具类//封装配置文件读取操作//封装Sessionfactroy创建操作//封装session获得操作public class HibernateUtils {private static SessionFactory sf;static{//1加载配置Configuration ?conf = new Configuration().configure();//2 根据Configuration 配置信息创建 SessionFactorysf = conf.buildSessionFactory();//Runtime.getRuntime().addShutdownHook(new Thread(new Runnable() {@Overridepublic void run() {System.out.println("虚拟机关闭!释放资源");sf.close();}}));}public static org.hibernate.Session ?openSession(){//3 获得sessionSession session = sf.openSession();return session;}public static org.hibernate.Session ?getCurrentSession(){//3 获得sessionSession session = sf.getCurrentSession();return session;}public static void main(String[] args) {System.out.println(openSession());}}

package com.huhu.a_state;import com.huhu.domain.User;import com.huhu.utils.HibernateUtils;import org.hibernate.Session;/** * 对象的三种状态 */public class HibernateDemo1 { ???//三种状态 ???public void fun1() { ???????Session session = HibernateUtils.openSession(); ???????session.beginTransaction(); ???????//-------------------------------------- ???????User u = new User(); ?????????//status : 瞬时状态 ???????u.setName("tom"); ??????????//status : 瞬时状态 ???????u.setPassword("1234"); ?????//status : 瞬时状态 ???????//保存 ???????session.save(u); ???????????//status : 持久状态 ???????//调用save方法时,数据库有没有对应记录 ???????//没有记录，但最终会被同步到数据库中，仍时持久状态 ???????//-------------------------------------- ???????session.getTransaction().commit(); ?????//status : 持久状态 ???????session.close(); ???????????//status : 游离状态 ???} ???// 三种状态的转换 ?瞬时=》持久 ???public void fun2() { ???????Session session = HibernateUtils.openSession(); ???????session.beginTransaction(); ???????//-------------------------------------- ???????User u = new User(); ??????????//status : 瞬时状态 ???????u.setName("he"); ????????????//status : 瞬时状态 ???????u.setPassword("123456"); ????//status : 瞬时状态 ???????session.save(u); ????????????//status : 持久状态 ???????//-------------------------------------- ???????session.getTransaction().commit(); ?????//status : 持久状态 ???????//事务提交时会把持久对象保存到数据库 ???????//increment=>hibernate 自动查询最大id，然后生成主键 ???????//assigned =>自动生成主键 ???????session.close(); ???} ???// 瞬时=》游离 瞬时：没有关联没有id 游离：没有关联有id(与数据库对应的id) ???public void fun3() { ???????Session session = HibernateUtils.openSession(); ???????session.beginTransaction(); ???????//--------------------------------------//status : 持久状态 ???????User u = new User(); ???????u.setId(2); ????????//此时为游离状态 ???????//-------------------------------------- ???????session.getTransaction().commit(); ?????//status : 持久状态 ???????//事务提交时会把持久对象保存到数据库 ???????session.close(); ???} ???//持久=》瞬时1 持久：有关联，有id，瞬时：无关联无id ???public void fun4() { ???????Session session = HibernateUtils.openSession(); ???????session.beginTransaction(); ???????//--------------------------------------//status : 持久状态 ???????//通过get方法，得到持久状态对象 ???????User u = (User) session.get(User.class, 2); //持久状态 ???????//-------------------------------------- ???????session.getTransaction().commit(); ???????//事务提交时会把持久对象保存到数据库 ???????session.close(); ?//游离状态 ???????u.setId(null); ???} ???//持久=》瞬时1 ?持久：有关联，有id，瞬时：无关联无id ???public void fun5() { ???????Session session = HibernateUtils.openSession(); ???????session.beginTransaction(); ???????//--------------------------------------//status : 持久状态 ???????//通过get方法，得到持久状态对象 ???????User u = (User) session.get(User.class, 4); //持久状态 ???????session.evict(u); ??????//将User对象和session的关联移除 ???????u.setId(null); ?????????//瞬时对象 ???????//-------------------------------------- ???????session.getTransaction().commit(); ???????session.save(u); ???????//事务提交时会把持久对象保存到数据库 ???????session.close(); ?//游离状态 ???} ???// ?持久=》游离 ??持久：有关联，有id ???public void fun6() { ???????Session session = HibernateUtils.openSession(); ???????session.beginTransaction(); ???????//--------------------------------------//status : 持久状态 ???????//通过get方法，得到持久状态对象 ???????User u = (User) session.get(User.class, 4); //持久状态 ???????session.evict(u); ??????//将User对象和session的关联移除 ???????//-------------------------------------- ???????session.getTransaction().commit(); //游离 ???????session.close(); ?//游离状态 ???} ???// 游离=》瞬时 ?瞬时：无关联无id ???public void fun7() { ???????Session session = HibernateUtils.openSession(); ???????session.beginTransaction(); ???????//--------------------------------------//status : 持久状态 ???????//通过get方法，得到持久状态对象 ???????User u = (User) session.get(User.class, 4); //持久状态 ???????session.evict(u); ??????//瞬时 ???????u.setId(null); ?????????//瞬时 ???????//-------------------------------------- ???????session.getTransaction().commit(); //瞬时 ???????session.close(); ?//瞬时状态 ???} ???// ???游离=》持久 ?是否与session关联 ???public void fun8() { ???????Session session = HibernateUtils.openSession(); ???????session.beginTransaction(); ???????//--------------------------------------//status : 持久状态 ???????//通过get方法，得到持久状态对象 ???????User u = (User) session.get(User.class, 4); //持久状态 ???????session.evict(u); ??????//游离 ???????session.update(u); ?????//持久 ???????//-------------------------------------- ???????session.getTransaction().commit(); //持久 ?打印updata语句 ???????session.close(); ?//瞬时状态 ???} ???public void fun9() { ???????Session session = HibernateUtils.openSession(); ???????session.beginTransaction(); ???????//--------------------------------------// ???????//通过get方法，得到持久状态对象 ???????User u = (User) session.get(User.class, 4); ???????u.setName("nenen"); ???????//-------------------------------------- ???????session.getTransaction().commit(); ???????session.close(); ?//瞬时状态 ???} ???public static void main(String[] args) { ???????HibernateDemo1 d = new HibernateDemo1(); ???????//d.fun1(); ???????d.fun9(); ???}}