Hibernate检索策略之5.3.2一对一单向（主键）关联检索策略——Hibernate4究竟怎么玩

已经有段时间没有写博客了，总是这样那样的事情牵绊，不过深入学习测试依然继续，只是没有定时更新博客而已，抱歉了。

上节讲了一对一单向外键关联，这次讲一对一单向主键关联。

当然，主键关联和外键关联很相似，唯一的区别就是前者通过主动端主键把二者联系在一起，而后者通过主动端的外键联系在一起。还以Husband和Wife域模型为例，一对一种这个例子最好了，尤其是在中国。

先看一下被动端:

package com.bao.sample.retrieve.strategy.uotop;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

import com.bao.sample.base.domain.BaseDomain;
/**
 * @Description:一对一主键关联 被动端 passiveness primarykey
 * @author:bao
 * @date:Sep 3, 2012
 */
@Entity
@Table(name = "t_husbanduop")
public class HusbandUOP extends BaseDomain {

    private static final long serialVersionUID = 1L;

    private Integer id;
    private String name;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public HusbandUOP() {
        super();
    }

    public HusbandUOP(String name) {
        super();
        this.name = name;
    }

}

这里说被动段似乎不是很恰当，虽然从java代码看，从husband是无法导航出wife，不过，先卖个关子，大家可以看后面的DDL建表语句上。

主动端域代码：

package com.bao.sample.retrieve.strategy.uotop;

import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;

import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;
import org.hibernate.annotations.GenericGenerator;
import org.hibernate.annotations.Parameter;

import com.bao.sample.base.domain.BaseDomain;

/**
 * @Description:一对一单向主键关联  主动端 proactiveness primarykey
 * @author:bao
 * @date:Sep 3, 2012
 */
@Entity
@Table(name = "t_wifeuop")
public class WifeUOP extends BaseDomain {

    private static final long serialVersionUID = 1L;

    private Integer id;
    private String name;
    private HusbandUOP husband;

    @Id
    @GeneratedValue(generator = "wifeGenerator")
    @GenericGenerator(name = "wifeGenerator", strategy = "foreign", 
            parameters = { @Parameter(name = "property", value = "husband") })
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @OneToOne(fetch = FetchType.LAZY)
    @PrimaryKeyJoinColumn
    @Cascade(CascadeType.SAVE_UPDATE)
    public HusbandUOP getHusband() {
        return husband;
    }

    public void setHusband(HusbandUOP husband) {
        this.husband = husband;
    }

    public WifeUOP() {
        super();
    }

    public WifeUOP(String name, HusbandUOP husband) {
        super();
        this.name = name;
        this.husband = husband;
    }

}

在这里需要重点看一下wife域模型的id生成方式，wife是这里的含义是使用另一个相关对象husband的主键做为wife的主键。但这并不体现先sql语句中。

package com.bao.sample.retrieve.strategy.uotop;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.unitils.UnitilsJUnit4;
import org.unitils.spring.annotation.SpringApplicationContext;

public class HusbandAndWifeServiceTest extends UnitilsJUnit4 {

    @SpringApplicationContext({ "applicationContext.xml" })
    private ApplicationContext applicationContext;

    /**
     * @Description 级联保存<br />
     *              主动端关联被动端对象的get方法上的注解为//@Cascade(org.hibernate.annotations.CascadeType.SAVE_UPDATE)
     * 
     */
    @Test
    public void saveHusbandAndWifeWithCascade() {
        HusbandUOPService husbandUOPService = (HusbandUOPService) applicationContext.getBean("husbandUOPService");

        HusbandUOP wifeUO = new HusbandUOP("wife4");
        husbandUOPService.save(new WifeUOP("husband4", wifeUO));

    }

}

具体的sql语句我已经输出出来：

Hibernate: 
    drop table if exists t_husbanduop
Hibernate: 
    drop table if exists t_wifeuop
Hibernate: 
    create table t_husbanduop (
        id integer not null auto_increment,
        name varchar(255),
        primary key (id)
    )
Hibernate: 
    create table t_wifeuop (
        id integer not null,
        name varchar(255),
        primary key (id)
    )
Hibernate: 
    insert 
    into
        t_husbanduop
        (name) 
    values
        (?)
Hibernate: 
    insert 
    into
        t_wifeuop
        (name, id) 
    values
        (?, ?)

从DDL语句中可以看到，t_husbanduop表示自增的，而t_wifeuop却没有，这内部同步两个表主键的工作我想hibernate来做了吧，这点应该没错。
其他的使用与外键关联就一致了，在此就不在赘述了。