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Hello,World in Hibernate 入門

Posted on 2010-05-04 11:30 無所謂閱讀(373) 評論(1) 編輯收藏所屬分類: Hibernate

本文介紹如何用hibernate寫一個hello world 程序，以及說明Hibernate下的對象的識別。
1、配置文件hibernate.cfg.xml：

<? xml version = ' 1.0 ' encoding = ' utf-8 ' ?>

<! DOCTYPE hibernate - configuration PUBLIC

" -//Hibernate/Hibernate Configuration DTD 3.0//EN "

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

< hibernate - configuration >

< session - factory >

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

< property name = " connection.url " > jdbc:mysql: // localhost:3306/eg</property>

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

< property name = " connection.password " > 4864452 </ property >

< property name = " connection.pool_size " > 1 </ property >

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

< property name = " current_session_context_class " > thread </ property >

< property name = " cache.provider_class " > org.hibernate.cache.NoCacheProvider </ property >

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

<!-- Drop and re - create the database schema on startup

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

-->

< mapping resource = " eg/Message.hbm.xml " />

</ session - factory >

</ hibernate - configuration >

2、源文件：

package eg;

public class Message {

private Long id;

private String text;

private Message nextMessage;

public Message() {}

public Message(String text) {

this .text = text;

}

public void setId(Long id) {

this .id = id;

}

public void setText(String text) {

this .text = text;

}

public void setNextMessage(Message nextMessage) {

this .nextMessage = nextMessage;

}

public Long getId() {

return ( this .id);

}

public String getText() {

return ( this .text);

}

public Message getNextMessage() {

return ( this .nextMessage);

}

3、配置文件：Messsage.hbm.xml

<? 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 =" eg.Message "

table = " MESSAGE "

< id

name = " id "

column = " MESSAGE_ID "

type = " java.lang.Long "

< generator class = " native " />

</ id >

< property

name = " text "

type = " java.lang.String "

update = " true "

insert = " true "

column = " MESSAGE_TEXT "

< many - to - one

name = " nextMessage "

class = " jmuse.eg.Message "

cascade = " all "

outer - join = " auto "

update = " true "

insert = " true "

column = " NEXT_MESSAGE_ID "

</ class >

</ hibernate - mapping >

4、最后的包結構：

+ lib

antlr.jar

cglib.jar

asm.jar

asm - attrs.jars

commons - collections.jar

commons - logging.jar

hibernate3.jar

jta.jar

dom4j.jar

log4j.jar

＋src

+ eg

Message.java

Message.hbm.xml

TestMessage.java

hibernate.cfg.ml

log4j.properties

5、測試：

session.beginTransaction();

Message m = new Message( " hello,world " );

session.save(m);

session.getTransaction().commit();

session.close();

你會發現在數據庫中有一條信息了，id=1
Hibernate的對象識別是通過對象的Id 來識別的：
如：

我們剛才在數據庫中保存了一個Id為1的Message對象。

如果：

session.beginTraction();

Message m = new Message();

m.setId( new Long( 1 ));

m.setText( " This is another greeting " );

session.saveOrUpdate(m);

sesion.getTraction.commit();

你會發現Hibernate會自動的把剛才的對象進行更新，而不是保存一個新的對象。
這個例子有點極端，呵呵。能說明問題就可以了。

# re: Hello,World in Hibernate 入門 回復 更多評論

2012-05-17 09:44 by hqan

看不懂，也運行不起來，沒說清楚原理。

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