02、Hibernate开发步骤

<?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>

     <!-- 配置连接数据库的基本信息 -->

<property name="connection.username">root</property>

<property name="connection.password">root123</property>

<property name="connection.driver_class">com.mysql.jdbc.driver</property>

<property name="connection.url">jdbc:mysql:///hibernate5</property>

<!-- 配置 hibernate 的基本信息 -->

<!-- hibernate 指定数据库所使用的 sql 方言 -->

<property name="dialect">org.hibernate.dialect.mysqlinnodbdialect</property>

<!-- 指定程序运行时是否在控制台输出 sql 语句 -->

<property name="show_sql">true</property>

<!-- 指定是否对输出 sql 语句进行格式化 -->

<property name="format_sql">true</property>

<!-- 指定程序运行时是否在数据库自动生成数据表 -->

<property name="hbm2ddl.auto">update</property>

     <!-- 指定关联的 .hbm.xml 文件 -->

     <mapping resource="csah/com/cnblogs/www/news.hbm.xml" />

    </session-factory>

</hibernate-configuration>

1）问题：生成cfg.xml时候弹出右下角内容，然后按finish一直无反应怎么办？？

答：hibernate版本问题，就是第三行hibernate version那个选择低一点的版本 我看jar包是4.3.x的，我选了4.3的就ok了

package csah.com.cnblogs.www;

import java.util.date;

public class news {

private integer id;

private string title;

private string author;

private date date;

public date getdate() {

return date;

}

public news(string title, string author, date date) {

super();

this.title = title;

this.author = author;

this.date = date;

}

public void setdate(date date) {

this.date = date;

}

public integer getid() {

return id;

}

public void setid(integer id) {

this.id = id;

}

public string gettitle() {

return title;

}

public void settitle(string title) {

this.title = title;

}

public string getauthor() {

return author;

}

public void setauthor(string author) {

this.author = author;

}

public news() {

}

@override

public string tostring() {

return "news [id=" + id + ", title=" + title + ", author=" + author + ", date=" + date + "]";

}

}

<?xml version="1.0"?>

<!doctype hibernate-mapping public "-//hibernate/hibernate mapping dtd 3.0//en"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<!-- generated 2020-4-25 2:28:16 by hibernate tools 3.5.0.final -->

<hibernate-mapping package="csah.com.cnblogs.www">

    <class name="news" table="news">

        <id name="id" type="java.lang.integer">

            <column name="id" />

            <!-- 指定主键的生成方式, native: 使用数据库本地方式 -->

            <generator class="native" />

        </id>

        <property name="title" type="java.lang.string">

            <column name="title" />

        </property>

        <property name="author" type="java.lang.string">

            <column name="author" />

        </property>

        <property name="date" type="java.util.date">

            <column name="date" />

        </property>

    </class>

</hibernate-mapping>

1）问题：ids for this class must be manually assigned before calling save(): csah.com.cnblogs.www.news

答：我们只需要将<generator class="assigned " />设置为<generator class="native" />

package csah.com.cnblogs.www;

import static org.junit.jupiter.api.assertions.*;

import java.sql.date;

import org.hibernate.session;

import org.hibernate.sessionfactory;

import org.hibernate.transaction;

import org.hibernate.cfg.configuration;

import org.hibernate.service.serviceregistry;

import org.hibernate.service.serviceregistrybuilder;

import org.junit.jupiter.api.test;

import csah.com.cnblogs.www.*;

class hibernatetest {

@test

public void test() {

system.out.println("test1...");

//1. 创建一个 sessionfactory 对象

sessionfactory sessionfactory = null;

system.out.println("test2...");

//1). 创建 configuration 对象: 对应 hibernate 的基本配置信息和 对象关系映射信息

configuration configuration = new configuration().configure();

system.out.println("test3...");

//4.0 之前这样创建

// sessionfactory = configuration.buildsessionfactory();

//2). 创建一个 serviceregistry 对象: hibernate 4.x 新添加的对象

//hibernate 的任何配置和服务都需要在该对象中注册后才能有效.

serviceregistry serviceregistry =

new serviceregistrybuilder().applysettings(configuration.getproperties())

                           .buildserviceregistry();

system.out.println("test4...");

//3).

sessionfactory = configuration.buildsessionfactory(serviceregistry);

system.out.println("test5...");

//2. 创建一个 session 对象

session session = sessionfactory.opensession();

system.out.println("test6...");

//3. 开启事务

transaction transaction = session.begintransaction();

system.out.println("test7...");

//4. 执行保存操作

news news = new news("java", "atguigu", new date(new java.util.date().gettime()));

system.out.println("test8...");

session.save(news);

system.out.println("test9...");

//5. 提交事务

transaction.commit();

system.out.println("test10...");

//6. 关闭 session

session.close();

system.out.println("test11...");

//7. 关闭 sessionfactory 对象

sessionfactory.close();

system.out.println("test12...");

}

}

1）问题：org.hibernate.invalidmappingexception: could not parse mapping document from resource com/cnblogs/com/csah/news.hbm.xml

java.lang.classnotfoundexception: com.nblogs.com.csah.news

答：在news.hbm.xml中 class中的路径出现错误 没有找到'com.nblogs.com.csah.news'

2）问题：org.hibernate.mappingnotfoundexception: resource: com/cnblogs/com/csah/news.hbm.xml not found

答：指定关联的 .hbm.xml 文件路径没有找到

3）问题：duplicate entry 'java' for key 2

答：插入的数据已经存在