使用Hibernate处理集合元素

在使用Hibernate的过程中，需要对一个集合类型的元素操作。Hibernate支持List/Set/Map元素，在Hibernate的mapper中有List/Set/Bag/Map标签以支持这一特性。

向一个学生对象中插入多张照片

- Stduent.java

package com.java1234.hibernate.model;import java.util.List;public class Student {private int id;private String name;private List<String> pictures;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public List<String> getPictures() {return pictures;}public void setPictures(List<String> pictures) {this.pictures = pictures;}}

- 使用List - 插入的元素有序且允许重复

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping><class name="com.java1234.hibernate.model.Student" table="tb_student"><id name="id" column="stuId"><generator class="native"/></id><property name="name" column="stuName"/><list name="pictures" table="tb_picture"><key column="stuId"/><list-index column="picIndex"/><element column="picName" type="string"/></list></class></hibernate-mapping>

生成的数据库表结构

Hibernate: create table tb_picture (stuId integer not null, picName varchar(255), picIndex integer not null, primary key (stuId, picIndex))
Hibernate: create table tb_student (stuId integer not null auto_increment, stuName varchar(255), primary key (stuId))
Hibernate: alter table tb_picture add constraint FK_dpi255h9ltoc1glix2hq8r2og foreign key (stuId) references tb_student (stuId)

使用Set  - 元素不可重复且无序

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping><class name="com.java1234.hibernate.model.Student" table="tb_student"><id name="id" column="stuId"><generator class="native"/></id><property name="name" column="stuName"/><set name="pictures" table="tb_picture"><key column="stuId"/><element column="picName" type="string"/></set></class></hibernate-mapping>

生成的数据库表结构

Hibernate: create table tb_picture (stuId integer not null, picName varchar(255))
Hibernate: create table tb_student (stuId integer not null auto_increment, stuName varchar(255), primary key (stuId))
Hibernate: alter table tb_picture add constraint FK_dpi255h9ltoc1glix2hq8r2og foreign key (stuId) references tb_student (stuId)

使用Bag - 元素无序/可以重复

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping><class name="com.java1234.hibernate.model.Student" table="tb_student"><id name="id" column="stuId"><generator class="native"/></id><property name="name" column="stuName"/><idbag name="pictures" table="tb_picture"><collection-id type="integer" column="picId"><generator class="increment"/></collection-id><key column="stuId"/><element column="picName" type="string"/></idbag></class></hibernate-mapping>

生成的数据库表结构

Hibernate: create table tb_picture (stuId integer not null, picName varchar(255), picId integer not null, primary key (picId))
Hibernate: create table tb_student (stuId integer not null auto_increment, stuName varchar(255), primary key (stuId))
Hibernate: alter table tb_picture add constraint FK_dpi255h9ltoc1glix2hq8r2og foreign key (stuId) references tb_student (stuId)

使用Map

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping><class name="com.java1234.hibernate.model.Student" table="tb_student"><id name="id" column="stuId"><generator class="native"/></id><property name="name" column="stuName"/><map name="pictures" table="tb_picture"><key column="stuId"/><map-key column="picKey" type="string"/><element column="picName" type="string"/></map></class></hibernate-mapping>

生成的数据库表结构

Hibernate: create table tb_picture (stuId integer not null, picName varchar(255), picKey varchar(255) not null, primary key (stuId, picKey))
Hibernate: create table tb_student (stuId integer not null auto_increment, stuName varchar(255), primary key (stuId))
Hibernate: alter table tb_picture add constraint FK_dpi255h9ltoc1glix2hq8r2og foreign key (stuId) references tb_student (stuId)