JPA里面的one-to-one关系的单向映射实例源码。设有2个实体，雇员 和停车位 。一个雇员只能拥有一个停车位，一个停车位只能属于一个雇员，因此他们是1对1的关系。在1对1关系中，我们需要区分主导者和从属者，所谓的主导者就是拥有外键的实体。本例中我们将雇员设置为主导者。下面我们用sql语句建立者两个表（基于MySql5.1数据库系统）：

– 创建EMPLOYEE表 –

CREATE TABLE EMPLOYEE(
ID INTEGER NOT NULL AUTO_INCREMENT ,
PSPACE_ID INTEGER NOT NULL ,
NAME VARCHAR (20) NOT NULL ,
SALARY INTEGER NOT NULL ,
LAST_UPDATED_TIME TIMESTAMP NOT NULL ,
PRIMARY KEY (ID),
FOREIGN KEY (PSPACE_ID) REFERENCES PARKING_SPACE (ID)
);
– 创建PARKING_SPACE表 –
CREATE TABLE PARKING_SPACE(
ID INTEGER NOT NULL AUTO_INCREMENT ,
LOT INTEGER NOT NULL ,
LOCATION VARCHAR (100) NOT NULL ,
LAST_UPDATED_TIME TIMESTAMP NOT NULL ,
PRIMARY KEY (ID)
);

接下来编写Employee类和ParkingSpace类：

package andycpp; 
import java.io.Serializable;
import java.util.Date;
import javax.persistence.*;
@Entity(name=”parking_space”)
public class ParkingSpace implements Serializable {
@Id
@Column(name=”ID”, nullable=false)
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Long id;

@Column(name=”LOT”, nullable=false)
private int lot;

@Column(name=”LOCATION”, nullable=false)
private String location;

@Version
@Column(name=”LAST_UPDATED_TIME”, nullable=false)
private Date updateTime;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public int getLot() {
return lot;
}
public void setLot(int lot) {
this.lot = lot;
}
public String getLocation() {
return location;
}
public void setLocation(String location) {
this.location = location;
}
public Date getUpdateTime() {
return updateTime;
}
public void setUpdateTime(Date updateTime) {
this.updateTime = updateTime;
}

private static final long serialVersionUID = 1760382073923264461L;
}

 

package andycpp;
import java.io.Serializable;
import javax.persistence.*;
@Entity(name=”employee”)
public class Employee implements Serializable {

@Id
@Column(name=”ID”, nullable=false)
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Long id;

@Column(name=”NAME”, nullable=false)
private String name;

@Column(name=”SALARY”, nullable=false)
private int salary;

@OneToOne(cascade=CascadeType.ALL)
@JoinColumn(name=”PSPACE_ID”)
private ParkingSpace pSpace;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getSalary() {
return salary;
}
public void setSalary(int salary) {
this.salary = salary;
}
public ParkingSpace getpSpace() {
return pSpace;
}
public void setpSpace(ParkingSpace pSpace) {
this.pSpace = pSpace;
}

}

[java] view plaincopy
//逆向连接的Inverse端
package andycpp;
import java.io.Serializable;
import java.util.Date;
import javax.persistence.*;
@Entity
@Table(name=”parking_space”)
public class ParkingSpace implements Serializable {
@Id
@Column(name=”ID”, nullable=false)
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Long id;

@Column(name=”LOT”, nullable=false)
private int lot;

@Column(name=”LOCATION”, nullable=false)
private String location;

@Version
@Column(name=”LAST_UPDATED_TIME”, nullable=false)
private Date updateTime;

@OneToOne(mappedBy=”pSpace”)
private Employee employee;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public int getLot() {
return lot;
}
public void setLot(int lot) {
this.lot = lot;
}
public String getLocation() {
return location;
}
public void setLocation(String location) {
this.location = location;
}
public Date getUpdateTime() {
return updateTime;
}
public void setUpdateTime(Date updateTime) {
this.updateTime = updateTime;
}

public Employee getEmployee() {
return employee;
}
public void setEmployee(Employee employee) {
this.employee = employee;
}

private static final long serialVersionUID = 1760382073923264461L;
}