myeclipse试用小记----Hibernate多对一自身关联（3）-白红宇

说明：一个部门有若干个子部门，子部门还可以有子部门，本文通过这个演示myeclipse如何实现这种树形关系的持久化。

开发工具：myeclipse 5.5.1 GA

数据库：mysql-5.0.37

操作系统：windows xp professional 中文版

步骤：

1、建立mysql5数据库testdb，脚本下面已经给出。

2、配置myeclipse的数据库服务器，并建立名称为mysql5的数据库链接。

3、建议myeclipse的web工程，名称为dx_d2yzs，并加入hibernate支持，选择hibernate3.1，最高就支持到3.1。

4、在myeclipse的数据库视图中链接数据库并通过表生成实体PO和配置文件，中间不生成DAO。

5、检查配置文件的正确性，然后测试类进行测试。

一、建立数据库的脚本:

drop table if exists part;

-- alter table part drop foreign key fk_part;

create table part(

id bigint not null primary key,

name varchar(20),

father_id bigint

);

alter table part add index fk_part (father_id),

add constraint fk_part foreign key (father_id) references part(id);

表关系的逻辑图：

+-----------+

| Part |

+-----------+

| id |<---------|<PK>

| name | |

| father_id |----------|<FK>

+-----------+

特别注意：因为有外键约束，需要事务支持，在安装数据库的时候，需要配置mysql数据库服务器的参数。数据库的引擎应该用InnoDB，关闭了自动提交模式，也就是SET AUTOCOMMIT=0。

my.ini

------------------------------------

#[WinMySQLAdmin]

#Server=D:/mysql-5.0.37-win32/bin/mysqld.exe

[mysqld]

# set basedir to your installation path

#basedir=D:/mysql-5.0.37-win32

# set datadir to the location of your data directory

port = 3306

key_buffer = 16K

max_allowed_packet = 1M

table_cache = 4

sort_buffer_size = 64K

read_buffer_size = 256K

read_rnd_buffer_size = 256K

net_buffer_length = 2K

thread_stack = 64K

datadir=data

default-character-set=gbk

init_connect='SET AUTOCOMMIT=0'

default-table-type=InnoDB

init_connect='set completion_type=1'

[client]

default-character-set=gbk

------------------------------------

二、通过myeclipse生成实体和配置文件：

Part.java

---------------------

public class Part implements java.io.Serializable {

// Fields

private Long id;

private String name;

private Part part; //父Part

private Set parts = new HashSet(0); //字Part

// Constructors

/** default constructor */

public Part() {

}

/** minimal constructor */

public Part(Long id) {

this.id = id;

}

public Part(String name) {

this.name = name;

}

/** full constructor */

public Part(Long id, Part part, String name, Set parts) {

this.id = id;

this.part = part;

this.name = name;

this.parts = parts;

}

// Property accessors

public Long getId() {

return this.id;

}

public void setId(Long id) {

this.id = id;

}

public Part getPart() {

return this.part;

}

public void setPart(Part part) {

this.part = part;

}

public String getName() {

return this.name;

}

public void setName(String name) {

this.name = name;

}

public Set getParts() {

return this.parts;

}

public void setParts(Set parts) {

this.parts = parts;

}

Part.hbm.xml

-------------------

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

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

" ">

<!--

Mapping file autogenerated by MyEclipse Persistence Tools

-->

<hibernate-mapping>

</id>

</property>

<many-to-one name="part" class="org.lavasoft.Part" fetch="select">

</many-to-one>

<key>

</key>

<one-to-many class="org.lavasoft.Part" />

</set>

</class>

</hibernate-mapping>

三、写测试类进行测试：

---------------------

package org.lavasoft;

import org.hibernate.HibernateException;

import org.hibernate.Session;

import org.hibernate.Transaction;

public class Test {

/**

* @param args

public static void main(String[] args) {

// TODO Auto-generated method stub

//if(HibernateSessionFactory.getSession()==null) System.out.println("null");

Part p1=new Part("p1");

Part p11=new Part("p11");

Part p12=new Part("p12");

p1.getParts().add(p11);

p1.getParts().add(p12);

p11.setPart(p1);

p12.setPart(p1);

Session session = HibernateSessionFactory.getSession();

Transaction tx=session.beginTransaction();

try {

session.save(p1);

tx.commit();

} catch (HibernateException e) {

// TODO Auto-generated catch block

e.printStackTrace();

tx.rollback();

}finally{

session.close();

}

四、运行测试类Test，控制台打印信息：

------------------------------------------

Hibernate: select max(id) from part

Hibernate: insert into part (name, father_id, id) values (?, ?, ?)

查看数据库：

------------------------------------------

D:\mysql-5.0.37-win32\bin>mysql -uroot -pleizhimin

Welcome to the MySQL monitor. Commands end with ; or \g.

Your MySQL connection id is 13

Server version: 5.0.37-community MySQL Community Edition (GPL)

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> use testdb;

Database changed

mysql> show tables;

+------------------+

| Tables_in_testdb |

+------------------+

| card |

| customers |

| orders |

| part |

| person |

| t_user |

| user |

+------------------+

7 rows in set (0.02 sec)

mysql> describe part;

+-----------+-------------+------+-----+---------+-------+

+-----------+-------------+------+-----+---------+-------+

| id | bigint(20) | NO | PRI | | |

+-----------+-------------+------+-----+---------+-------+

3 rows in set (0.00 sec)

mysql> select * from part;

+----+------+-----------+

| id | name | father_id |

+----+------+-----------+

| 1 | p1 | NULL |

| 2 | p12 | 1 |

| 3 | p11 | 1 |

+----+------+-----------+

3 rows in set (0.00 sec)

mysql>

测试结果表明，保存父机关的时候，可以级联保存父机关下的子机关。

总结：这个表建立好后，由myeclipse生成的PO不需要做任何改动，生成的mapping也需要添加一个cascade="save-update"。然后就直接写测试类进行测试。

本文转自 leizhimin 51CTO博客，原文链接：http://blog.51cto.com/lavasoft/30183，如需转载请自行联系原作者