Question

我有2个Mysql表用户和帝国，用户

CREATE TABLE `users` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`email` varchar(45) CHARACTER SET utf8 NOT NULL,
`password` varchar(12) CHARACTER SET utf8 NOT NULL,
`country` varchar(25) CHARACTER SET utf8 NOT NULL,
`activated` tinyint(3) unsigned NOT NULL DEFAULT '0',
`activationcode` varchar(45) CHARACTER SET utf8 NOT NULL DEFAULT '',
PRIMARY KEY (`id`),
UNIQUE KEY `email_UNIQUE` (`email`),
KEY `email` (`email`)
) ENGINE=InnoDB AUTO_INCREMENT=19 DEFAULT CHARSET=utf8    COLLATE=utf8_unicode_ci;

和帝国

CREATE TABLE `empires` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`pid` int(10) unsigned NOT NULL,
`name` varchar(45) CHARACTER SET utf8 NOT NULL,
`notes` varchar(90) CHARACTER SET utf8 NOT NULL,
`world` tinyint(3) unsigned NOT NULL,
`island` smallint(5) DEFAULT NULL,
`population` int(10) unsigned DEFAULT '20',
`gold` decimal(20,0) DEFAULT '500',
`percent` decimal(9,5) DEFAULT '50.00000',
`logo` varchar(30) COLLATE utf8_unicode_ci NOT NULL DEFAULT '',
PRIMARY KEY (`id`,`pid`),
KEY `name` (`name`),
KEY `world` (`world`),
KEY `FK_pid` (`pid`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

我有这些实体：

package boddooo.entity;

import java.io.Serializable;
import javax.persistence.*;

@Entity
@Table(name="users")
@NamedQuery(name="User.findAll", query="SELECT u FROM User u")
public class User implements Serializable {
private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;
private int activated=1;
private String activationcode="";
private String country;
private String email;
private String password;

public User(){}
public User(int id,String email,String password,String country) {
    this.id=id;
    this.email=email;
    this.password=password;
    this.country=country;
}

public int getId() {
    return this.id;
}

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

public int getActivated() {
    return this.activated;
}

public void setActivated(int activated) {
    this.activated = activated;
}

public String getActivationcode() {
    return this.activationcode;
}

public void setActivationcode(String activationcode) {
    this.activationcode = activationcode;
}

public String getCountry() {
    return this.country;
}

public void setCountry(String country) {
    this.country = country;
}

public String getEmail() {
    return this.email;
}

public void setEmail(String email) {
    this.email = email;
}

public String getPassword() {
    return this.password;
}

public void setPassword(String password) {
    this.password = password;
}

}

和

package boddooo.entity;

import java.io.Serializable;
import java.math.BigDecimal;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQuery;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;

@Entity
@Table(name="empires")
@NamedQuery(name="Empire.findAll", query="SELECT e FROM Empire e")
public class Empire implements Serializable {
private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int id;

private int pid;
private BigDecimal gold=BigDecimal.valueOf(500);
private String logo="";
private String name;
private String notes;
private BigDecimal percent=BigDecimal.valueOf(50.0000);
private int population=10;
private int world;
private int island;

@OneToOne
@PrimaryKeyJoinColumn(name="pid")
private User user;

public User getUser() {
    return user;
}

public void setUser(User user) {
    this.user = user;
}

public Empire(){}
public Empire(int id,String name,String logo,String notes,int world) {
    this.id=id;
    this.name=name;
    this.logo=logo;
    this.notes=notes;
    this.world=world;
}

public int getPid() {
    return pid;
}
public void setPid(int pid){
    this.pid=pid;
}

public int getWorld() {
    return world;
}

public void setWorld(int world) {
    this.world = world;
}

public int getIsland() {
    return island;
}

public void setIsland(int island) {
    this.island = island;
}

public int getId() {
    return this.id;
}

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

public BigDecimal getGold() {
    return this.gold;
}

public void setGold(BigDecimal gold) {
    this.gold = gold;
}

public String getLogo() {
    return this.logo;
}

public void setLogo(String logo) {
    this.logo = logo;
}

public String getName() {
    return this.name;
}

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

public String getNotes() {
    return this.notes;
}

public void setNotes(String notes) {
    this.notes = notes;
}

public BigDecimal getPercent() {
    return this.percent;
}

public void setPercent(BigDecimal percent) {
    this.percent = percent;
}

public int getPopulation() {
    return this.population;
}

public void setPopulation(int population) {
    this.population = population;
}
}

和此函数将新的objets插入数据库

public void createUser() throws NamingException, NotSupportedException, SystemException, SecurityException, IllegalStateException, RollbackException, HeuristicMixedException, HeuristicRollbackException{
    Context icontext=new InitialContext();
    ut=(UserTransaction)icontext.lookup("java:comp/UserTransaction");
    ut.begin();
    User user=new User();
    user.setEmail(email);
    user.setPassword(password);
    user.setCountry(country);
    em.persist(user);
    Empire emp=new Empire();
    emp.setName(empirename);
    emp.setNotes(empirenotes);
    emp.setLogo(empirelogo);
    emp.setWorld(worldid);
    emp.setUser(user);
    em.persist(emp);
    ut.commit();
}

这是一对一的关系 empires.pid = users.id 但当我调用此方法时，它会插入用户和帝国，但帝国中的pid字段具有0值而不是自动增量值。我想念一下吗？请帮忙

Answer 1

@PrimaryKeyJoinColumn表示使用的字段是此实体主键，因此实际上是只读的。当您拥有跨多个表的实体时，通常会使用此方法。 @JoinColumn是您应该使用的，因为它表示指定的列是传统的外键，并且您希望使用目标值来设置此字段。

@OneToOne
@JoinColumn(name="pid")
private User user;

Answer 2

您应该使用@JoinColumn(name="fk_id")和@OneToOne。更多详情请见JSR 317: JavaTM Persistence API, Version 2.0

JPA one_to_one关系不检索自动增量

2 个答案: