引言:使用连接数据库来创建实体类,很快就学会了,但是对于怎么用hibernate创建数据表确实用了两天的时间,记录下这次学习的过程。
1、在一开始怎么都搜不到资料,后来才明白,在搜的时候要加正向的,用数据库创建实体类是反向,用实体类创建数据表是正向的,这样搜就可以了
2、在一开始的时候,总是执着于IDE和插件的问题,对于所遇到的问题没有进行深入的研究,导致浪费掉了大量的时间(最后还是没搞定)
3、总是执着于教程上的操作方式,到最后才发现,在新版本里的写法是不一样的,坑之又坑
4、浪费时间最长的是如何使用hibernate用实体类生成hbm.xml文件,在教程里看老师用的挺溜的,因为电脑的原因,ide、插件安装失败,所以最后是只能是手写了
1、创建hibernate项目:参考资料:https://blog.csdn.net/fighting_sxw/article/details/80566295(友情提示:注意测试时新版本与旧版本的书写方式)
2、在使用hibernate创建数据表需要四个主要文件:实体类,实体类对应的映射文件(后缀名为hbm.xml结尾),hibernate的配置文件(以cfg.xml结尾),以及测试类
3、对应的主要内容如下:
实体类:
package com.hibernate.entity; import java.util.Date; public class Students { private int sid; private String sname; private String gender; private Date birthday; private String address; public Students(){ } public Students(int sid, String sname, String gender, Date birthday, String address) { this.sid = sid; this.sname = sname; this.gender = gender; this.birthday = birthday; this.address = address; } public int getSid() { return sid; } public void setSid(int sid) { this.sid = sid; } public String getSname() { return sname; } public void setSname(String sname) { this.sname = sname; } public String getGender() { return gender; } public void setGender(String gender) { this.gender = gender; } public Date getBirthday() { return birthday; } public void setBirthday(Date birthday) { this.birthday = birthday; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } @Override public String toString() { return "Students{" + "sid=" + sid + ", sname=‘" + sname + ‘\‘‘ + ", gender=‘" + gender + ‘\‘‘ + ", birthday=" + birthday + ", address=‘" + address + ‘\‘‘ + ‘}‘; } }
实体类对应的hbm.xml文件
<?xml version="1.0" encoding="utf-8"?> <!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.hibernate.entity.Students" table="Students"> <id name="sid" type="int"> <column name="SID"/> <generator class="assigned"/> </id> <property name="sname" type="java.lang.String"> <column name="SNAME"/> </property> <property name="gender" type="java.lang.String"> <column name="GENDER"/> </property> <property name="birthday" type="java.util.Date"> <column name="BIRTHDAY"/> </property> <property name="address" type="java.lang.String"> <column name="ADDRESS"/> </property> </class> </hibernate-mapping>
hibernate的cfg文件
<?xml version=‘1.0‘ encoding=‘utf-8‘?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="connection.url">jdbc:mysql://localhost:3306/rushi</property> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.username">root</property> <property name="connection.password">Sys935269</property> <!-- DB schema will be updated if needed --> <!-- <property name="hbm2ddl.auto">update</property> --> <property name="show_sql">true</property> <property name="format_sql">true</property> <!--自动生成--> <property name="hbm2ddl.auto">create</property> <!--数据库方言--> <property name="hibernate.dialect">org.hibernate.dialect.MySQL55Dialect</property> <!--加载资源--> <mapping resource="com/hibernate/entity/Students.hbm.xml"/> </session-factory> </hibernate-configuration>
4、这里对测试类重点介绍下,测试的时候新版本与旧版本可能会有所不同,按照教程可能永远都找不出问题所在(参考资料:https://blog.csdn.net/bingjianit/article/details/68954250)
package com.hibernate.entity; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.boot.Metadata; import org.hibernate.boot.MetadataSources; import org.hibernate.boot.registry.StandardServiceRegistry; import org.hibernate.boot.registry.StandardServiceRegistryBuilder; import org.hibernate.cfg.Configuration; import org.junit.After; import org.junit.Before; import java.util.Date; public class Test { private SessionFactory sessionFactory; private Session session; private Transaction transaction; @Before public void init() { //创建配置对象 //Configuration configure = new Configuration().configure(); //创建服务注册对象 //ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build(); ////以上为旧版本的写法,若是不注意,就会报org.hibernate.MappingException: Unknown entity: com.hibernate.entity.Student这个错误 StandardServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().configure().build(); //创建会话工厂对象 SessionFactory sessionFactory = new MetadataSources(serviceRegistry).buildMetadata().buildSessionFactory(); //会话对象 session = sessionFactory.openSession(); //开启事务 transaction = session.beginTransaction(); } @After public void destory() { //提交事务 transaction.commit(); //关闭会话 session.close(); //关闭会话工厂 sessionFactory.close(); } @org.junit.Test public void TestSaveStudents() { //生成学生对象 Students s = new Students(2, "张三丰", "南", new Date(), "武当山"); session.save(s); } }
程序运行结束,可能提示运行失败,但是数据已经存在表格里了,不确定的可以去数据里查看下
格言:从不熟悉到熟悉是一个过程,无需恐惧,
原文地址:https://www.cnblogs.com/lindaiyu/p/10990525.html