关于hibernate学习第一天出现的错误以及最后的代码

最新推荐文章于 2022-07-08 10:45:37 发布

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最新推荐文章于 2022-07-08 10:45:37 发布

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分类专栏： hibernate 文章标签： hibernate

本文链接：https://blog.youkuaiyun.com/jywhpu0612/article/details/86749459

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本文详细记录了hibernate学习的第一天，从项目的准备工作到编写配置文件、持久化类和对象关系映射，再到遇到的entity未知和执行语句错误的问题。针对这些问题，作者分析了原因并提供了相应的解决方案，如hibernate版本差异导致的初始化方法变化和配置文件的调整。通过junit测试验证了修正后的代码能正常运行。

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一.准备工作

1.在eclipse安装好hibernate tools以便框架的开发

2.下载hibernate后，创建一个名为hibernate_001的java项目，导入hibernate中lib/required的所有jar包，同时导入junit和mysql的jar包

3.准备工作完成后可以开始编写hibernate

二.编写hibernate例子

1.新建一个hibernate配置文件(cfg.xml)

2.编写hibernate.cfg.xml

<?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>
        <!-- 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">123</property>
		<!-- hibernate.connection.url : 连接数据库的地址,路径 -->
		<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate?useUnicode=true&amp;characterEncoding=UTF-8</property>
		<!-- 数据库方言配置 org.hibernate.dialect.MySQLDialect (选择最短的)-->
        <property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</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>
		<!-- 指定hibernate启动的时候自动创建表结构creat update -->
		<property name="hbm2ddl.auto">create</property>
		</session-factory>
</hibernate-configuration>

3.创建一个持久化类Students.java

import java.util.Date;

public class Students {
	
	private int sid;
	private String sname;
	private String gendar;
	private Date birthday;
	private String address;
	
	public Students(){
		super();
	}
	
	public Students(int sid, String sname, String gendar, Date birthday, String address) {
		super();
		this.sid = sid;
		this.sname = sname;
		this.gendar = gendar;
		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 getGendar() {
		return gendar;
	}

	public void setGendar(String gendar) {
		this.gendar = gendar;
	}

	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 + ", gendar=" + gendar + ", birthday=" + birthday
				+ ", address=" + address + "]";
	}
	
	
	
}

4.创建一个对象——关系映射文件（hbm.xml）

为上一步的持久化类创建对象关系映射文件Students.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">
<!-- Generated 2019-2-1 20:23:07 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping>
    <class name="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="gendar" type="java.lang.String">
            <column name="GENDAR" />
        </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>

5.在之前的配置文件中加一句

<mapping resource="Students.hbm.xml"/>

6.编写junit测试类

在项目中new一个source folder名为test

创建StudentsTest类

import java.util.Date;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class StudentsTest {
	
	private SessionFactory sessionFactory;
	private Session session;
	private Transaction transaction;
	
	@Before
	public void init(){
		//创建配置对象  
        Configuration config = new Configuration().configure();
        //创建服务注册对象  
        ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(config .getProperties()).build();
        //创建会话工厂对象  
        sessionFactory = config.buildSessionFactory(serviceRegistry);
        //会话对象  
        session = sessionFactory.openSession();
        //开启事务  
        transaction = session.beginTransaction();
	}
	
	@After
	public void destroy(){
		transaction.commit();//提交事务
		session.close();//关闭会话
		sessionFactory.close();//关闭会话工厂
	}
	
	@Test
	public void testSaveStudents(){
		Students s = new Students(1,"张三","男",new Date(),"武汉");
		session.save(s);//保存对象进入数据库
	}
}

7.用junit测试testSaveStudents方法

8.测试结果

二月 02, 2019 2:21:57 下午 org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {5.3.7.Final}
二月 02, 2019 2:21:57 下午 org.hibernate.cfg.Environment <clinit>
INFO: HHH000206: hibernate.properties not found
二月 02, 2019 2:21:57 下午 org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit>
INFO: HCANN000001: Hibernate Commons Annotations {5.0.4.Final}
二月 02, 2019 2:21:57 下午 org.hibernate.boot.jaxb.internal.stax.LocalXmlResourceResolver resolveEntity
WARN: HHH90000012: Recognized obsolete hibernate namespace http://hibernate.sourceforge.net/hibernate-mapping. Use namespace http://www.hibernate.org/dtd/hibernate-mapping instead.  Support for obsolete DTD/XSD namespaces may be removed at any time.
二月 02, 2019 2:21:58 下午 org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH10001002: Using Hibernate built-in connection pool (not for production use!)
二月 02, 2019 2:21:58 下午 org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001005: using driver [com.mysql.jdbc.Driver] at URL [jdbc:mysql://localhost:3306/hibernate?useUnicode=true&characterEncoding=UTF-8]
二月 02, 2019 2:21:58 下午 org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {user=root, password=****}
二月 02, 2019 2:21:58 下午 org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
二月 02, 2019 2:21:58 下午 org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl$PooledConnections <init>
INFO: HHH000115: Hibernate connection pool size: 20 (min=1)
二月 02, 2019 2:21:58 下午 org.hibernate.dialect.Dialect <init>
INFO: HHH000400: Using dialect: org.hibernate.dialect.MySQL5Dialect
Hibernate: 
    
    drop table if exists STUDENTS
二月 02, 2019 2:21:59 下午 org.hibernate.resource.transaction.backend.jdbc.internal.DdlTransactionIsolatorNonJtaImpl getIsolatedConnection
INFO: HHH10001501: Connection obtained from JdbcConnectionAccess [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess@5b6e8f77] for (non-JTA) DDL execution was not in auto-commit mode; the Connection 'local transaction' will be committed and the Connection will be set into auto-commit mode.
Hibernate: 
    
    create table STUDENTS (
       SID integer not null,
        SNAME varchar(255),
        GENDAR varchar(255),
        BIRTHDAY datetime,
        ADDRESS varchar(255),
        primary key (SID)
    ) engine=MyISAM
二月 02, 2019 2:21:59 下午 org.hibernate.resource.transaction.backend.jdbc.internal.DdlTransactionIsolatorNonJtaImpl getIsolatedConnection
INFO: HHH10001501: Connection obtained from JdbcConnectionAccess [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess@2caf6912] for (non-JTA) DDL execution was not in auto-commit mode; the Connection 'local transaction' will be committed and the Connection will be set into auto-commit mode.
二月 02, 2019 2:21:59 下午 org.hibernate.tool.schema.internal.SchemaCreatorImpl applyImportSources
INFO: HHH000476: Executing import script 'org.hibernate.tool.schema.internal.exec.ScriptSourceInputNonExistentImpl@22101c80'
Hibernate: 
    insert 
    into
        STUDENTS
        (SNAME, GENDAR, BIRTHDAY, ADDRESS, SID) 
    values
        (?, ?, ?, ?, ?)
二月 02, 2019 2:21:59 下午 org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
INFO: HHH10001008: Cleaning up connection pool [jdbc:mysql://localhost:3306/hibernate?useUnicode=true&characterEncoding=UTF-8]

三.总结

1.关于测试过程中出现unknown entity，原因出自hibernate版本问题init方法的写法不同

hibernate4.3之前写法

    @Before
	public void init(){  
        Configuration config = new Configuration().configure();
        ServiceRegistry serviceRegistry = new SerivceRegistryBuilder().applySettings(config.getProperties()).build();
        sessionFactory = config.buildSessionFactory(serviceRegistry);
        session = sessionFactory.openSession();
        transaction = session.beginTransaction();
	}

2.测试中出现hibernate could not execute statement

使用hibernate5导致，要在之前配置文件中修改

原来这样写

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

hibernate5要修改为

<property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</property>