Hibernate笔记

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1) 主键生成方式

assigned：指派，即由用户自行管理

//HBM根元素指定POJO类所在的包<hibernate-mapping package=" POJO类所在的包路径">

//指定Person类与PERSON表的映射 <class name="Person"table="PERSON">

//name表示Person类中的属性名字 //column：表示表中的字段名字 //type：类型

//主键的生成方式：assigned：表示由用户自行管理 <generator class="assigned"/>

</id>

//表示Person类中与表中其他字段的映射

//name：Person类中的属性名称

//column：表中的字段名称

//type：类型

//not-null：不允许为空

</class>

</hibernate-mapping>

此文件完成Person类到PERSON表的关系

取得操作数据库的Session：

Session是一个接口，必须通过其他类实例化，格式是固定的

//找到Hibernate配置

Configuration config=new Configuration().configure();

//从配置中取出SessionFactory

SessionFactory factory=config.buildSessionFactory();

//从SessionFactory中取出一个Session

this.session=factory.openSession();

通过正常配置之后，发现数据无法存入

事务处理，在插入完成之后，必须将事务提交：Transaction

使用Hibernate操作数据库，代码量很少，由Hibernate完成

用户就感觉像使用对象一样去使用数据库

所有的操作过程都是通过POJO类完成

主键生成方式：assigned：指派

·Sequence：自动增长的数据段

·uuid.hex：生成一个32位，不会重复的主键

2) 实体映射-粒度设计

☆ 所谓的细粒度划分，是指在POJO类上的面向对象的划分，而不在于表的划分上.

例如: 配置文件：

<?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 package=" POJO类所在的包路径">

</id>

</component>

E-Mail：mldnqa@163.com<component name="contact"class="org.lxh.hibernate.Contact">

</component>

</class>

</hibernate-mapping>

3) 复合主键

如果要实现复合主键，首先类应该先满足以下要求：

1、本类必须实现Serializable接口

2、复写equals和hashCode方法

·equals：对象比较方法

·hashCode：取得Hash编码

对于equals和hashCode方法的复写，可以使用第三方工具：commons-lang-1.0.1.jar

方法一:Persion.java

import java.io.Serializable;

import org.apache.commons.lang.builder.EqualsBuilder;

import org.apache.commons.lang.builder.HashCodeBuilder;

public class Person implements Serializable {

private String name;

private String phone;

private int age;

public boolean equals(Object obj) {

// TODO 自动生成方法存根

if (this == obj) {

return true;

}

if (!(obj instanceof Person)) {

return false;

}

Person p = (Person) obj;

return new EqualsBuilder().append(this.name, p.name).append(this.phone,

p.phone).append(this.age, p.age).isEquals();

}

public int hashCode() {

// TODO 自动生成方法存根

return new HashCodeBuilder().append(this.name).append(this.age).append(

this.phone).toHashCode();

}

Setter/getter….

}

Person.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 package=" POJO类所在的包路径">

<composite-id>

<key-property name="name" column="NAME" type="string"/>

<key-property name="phone" column="PHONE" type="string"/>

</composite-id>

</class>

</hibernate-mapping>

方法二:使用主键类

PersonKey.java

* WARNING: DO NOT EDIT THIS FILE. This is a generated file that is synchronized

* by MyEclipse Hibernate tool integration.

* Created Sat Nov 11 21:36:22 CST 2006 by MyEclipse Hibernate Tool.

import java.io.Serializable;

import org.apache.commons.lang.builder.EqualsBuilder;

import org.apache.commons.lang.builder.HashCodeBuilder;

/**

* A class representing a composite primary key id for the PERSON

* table. This object should only be instantiated for use with instances

* of the Person class.

* WARNING: DO NOT EDIT THIS FILE. This is a generated file that is synchronized

* by MyEclipse Hibernate tool integration.

public class PersonKey

implements Serializable

{

/** The cached hash code value for this instance. Settting to 0 triggers re-calculation. */

private volatile int hashValue = 0;

/** The value of the NAME component of this composite id. */

private java.lang.String name;

/** The value of the PHONE component of this composite id. */

private java.lang.String phone;

/**

* Simple constructor of PersonKey instances.

public PersonKey()

{

}

/**

* Returns the value of the name property.

* @return java.lang.String

public java.lang.String getName()

{

return name;

}

/**

* Sets the value of the name property.

* @param name

public void setName(java.lang.String name)

{

hashValue = 0;

this.name = name;

}

/**

* Returns the value of the phone property.

* @return java.lang.String

public java.lang.String getPhone()

{

return phone;

}

/**

* Sets the value of the phone property.

* @param phone

public void setPhone(java.lang.String phone)

{

hashValue = 0;

this.phone = phone;

}

/**

* Implementation of the equals comparison on the basis of equality of the id components.

* @param rhs

* @return boolean

public boolean equals(Object obj)

{

if (this == obj) {

return true;

}

if (!(obj instanceof Person)) {

return false;

}

PersonKey p = (PersonKey) obj;

return new EqualsBuilder().append(this.name, p.getName()).append(this.phone,

p.getPhone()).isEquals();

}

/**

* Implementation of the hashCode method conforming to the Bloch pattern with

* the exception of array properties (these are very unlikely primary key types).

* @return int

public int hashCode()

{

return new HashCodeBuilder().append(this.name).append(

this.phone).toHashCode();

}

Person.java

import java.io.Serializable;

import org.apache.commons.lang.builder.EqualsBuilder;

import org.apache.commons.lang.builder.HashCodeBuilder;

public class Person implements Serializable {

private PersonKey id ;

private int age;

setter/getter…

}

Person.hbm.mxl

<?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 package=" POJO类所在的包路径">

<composite-id name="id" class="PersonKey">

<key-property name="name" column="NAME" type="string"/>

<key-property name="phone" column="PHONE" type="string"/>

</composite-id>

</class>

</hibernate-mapping>

4) 实体层设计

方法一: 数据库结构CREATE TABLE TItem

(

id varchar(32) not null primary key ,

name varchar(20) not null ,

manufacturer varchar(20)

) ;

CREATE TABLE TBook

(

id varchar(32) not null primary key ,

pagecount int

) ;

CREATE TABLE TDvd

(

id varchar(32) not null primary key ,

regioncode varchar(2)

) ;

TItem.java

public class TItem {

private String id ;

private String name ;

private String manufacturer ;

setter/getter…

}

TDVD.java

public class TDVD extends TItem {

private String regionCode ;

setter/getter…

}

TBook.java

public class TBook extends TItem {

private int pageCount ;

setter/getter…

}

Titem.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 package="POJO类所在的包路径">

</id>

<joined-subclass name="org.lxh.hibernate04.TBook" table="TBook">

</joined-subclass>

<joined-subclass name="org.lxh.hibernate04.TDVD" table="TDvd">

</joined-subclass>

</class>

</hibernate-mapping>

方法一: 数据库结构

CREATE TABLE TItem

(

id varchar(32) not null primary key ,

-- 通过此字段用于区分保存的是 Book还是 DVD

category varchar(2) not null ,

name varchar(20) not null ,

manufacturer varchar(20) not null ,

regionCode varchar(2) ,

pageCount int

)

TItem.java

public class TItem {

private String id ;

private String name ;

private String manufacturer ;

setter/getter…

}

TDVD.java

public class TDVD extends TItem {

private String regionCode ;

setter/getter…

}

TBook.java

public class TBook extends TItem {

private int pageCount ;

setter/getter…

}

Titem.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 package="org.lxh.hibernate05">

</id>

</subclass>

</subclass>

</class>

</hibernate-mapping>