使用Subselect标签构造持久类查询

来源：互联网发布：21天学通java怎么样编辑：程序博客网时间：2024/06/06 20:48

前面文章阐述了，如果在Container,Box,Bottle三者的继承关系中配置HBM文件（box,bottle继承自Container）

现在，有一种更加简便的方式，使数据库中不需要建立一个box。bottle共享的表，而是分别建立Box和Bottle的表，这样更加复合面向对象的思想，而查询container则通过HBM配置文件来进行

Container持久类其中Xparam,Yparam,Zparam对应box，bottle中的length等属性，只要保证都能包括Box,Bottle中的属性就可以，也就是说container属性是Box和Bottle和合集

本例子使用了hilo主键生成器策略所以，需要在数据库中建立一张维护高位值的表，并给出一个高位数值

CREATE TABLE `box` (

`id` int(11) NOT NULL default '0',

`size` double default NULL,

`name` varchar(50) default NULL,

`description` varchar(50) default NULL,

`width` double default NULL,

`height` double default NULL,

`len` double default NULL,

PRIMARY KEY (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=gb2312;

CREATE TABLE `bottle` (

`id` int(11) NOT NULL default '0',

`size` double default NULL,

`name` varchar(20) default NULL,

`diameter` double default NULL,

`height` double default NULL,

`description` varchar(50) default NULL,

PRIMARY KEY (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=gb2312;

CREATE TABLE `hibernate_unique_key` (

`next_hi` int(11) NOT NULL default '0',

PRIMARY KEY (`next_hi`)

) ENGINE=InnoDB DEFAULT CHARSET=gb2312;

package subselect;

public class Container {

private String id;

private double size;

private String name;

private String description;

private double xparam;

private double yparam;

private double zparam;

public String getDescription() {

return description;

}

public void setDescription(String description) {

this.description = description;

}

public String getId() {

return id;

}

public void setId(String id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public double getSize() {

return size;

}

public void setSize(double size) {

this.size = size;

}

public double getXparam() {

return xparam;

}

public void setXparam(double xparam) {

this.xparam = xparam;

}

public double getYparam() {

return yparam;

}

public void setYparam(double yparam) {

this.yparam = yparam;

}

public double getZparam() {

return zparam;

}

public void setZparam(double zparam) {

this.zparam = zparam;

}

Box持久类

package subselect;

public class Box {

private int id;

private double size;

private String name;

private String description;

private double width;

private double length;

private double height;

public String getDescription() {

return description;

}

public void setDescription(String description) {

this.description = description;

}

public double getHeight() {

return height;

}

public void setHeight(double height) {

this.height = height;

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public double getLength() {

return length;

}

public void setLength(double length) {

this.length = length;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public double getSize() {

return size;

}

public void setSize(double size) {

this.size = size;

}

public double getWidth() {

return width;

}

public void setWidth(double width) {

this.width = width;

}

Bottle持久类

package subselect;

public class Bottle {

private int id;

private double size;

private String name;

private String description;

private double diameter;

private double height;

public String getDescription() {

return description;

}

public void setDescription(String description) {

this.description = description;

}

public double getDiameter() {

return diameter;

}

public void setDiameter(double diameter) {

this.diameter = diameter;

}

public double getHeight() {

return height;

}

public void setHeight(double height) {

this.height = height;

}

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 double getSize() {

return size;

}

public void setSize(double size) {

this.size = size;

}

Mapping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">

<!--

Mapping file autogenerated by MyEclipse - Hibernate Tools

-->

<hibernate-mapping package="subselect">

select id,size,name,description,diameter as xparam,diameter as yparam,height as zparam from Bottle

union

select id,size,name,description,width as xparam,len as yparam,height as zparam from Box

</subselect>

</id>

</class>

</hibernate-mapping>

<?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">

<!--

Mapping file autogenerated by MyEclipse - Hibernate Tools

-->

<hibernate-mapping package="subselect">

</id>

</class>

</hibernate-mapping>

<?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">

<!--

Mapping file autogenerated by MyEclipse - Hibernate Tools

-->

<hibernate-mapping package="subselect">

</id>

</class>

</hibernate-mapping>

测试代码：

package subselect;

import java.util.List;

import org.hibernate.Query;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.Transaction;

import org.hibernate.cfg.Configuration;

public class test {

/**

* @param args

public static void main(String[] args) {

Configuration cfg=new Configuration();

cfg.configure();

SessionFactory sf=cfg.buildSessionFactory();

Session session=sf.openSession();

Transaction t=session.beginTransaction();

Box box=new Box();

box.setName("纸箱子");

box.setSize(100);

box.setDescription("装电视机");

box.setLength(100);

box.setWidth(200);

Bottle bottle=new Bottle();

bottle.setName("空瓶子");

bottle.setSize(100);

bottle.setHeight(100);

bottle.setDiameter(100);

bottle.setDescription("喝牛奶用");

session.save(box);

session.save(bottle);

t.commit();

Query query=session.createQuery("from Container");

List a=query.list();

for(int i=0;i<a.size();i++){

Container c=(Container)a.get(i);

System.out.println(c.getId()+"-"+c.getName());

}

System.out.println("success");

}