JPA一对一关系练习

Posted 2021-01-24 jiangchanglin

汽车的属性有：id、品牌、型号、颜色、价格；

车牌的属性有：车牌号、类型（军用、民用等）、材质、颜色等

A、老刘新买了一辆汽车，并且上了新车牌； （两个表中创建）
B、老刘的小车被小偷偷走了，又买了一辆新车，但是车牌不变； （创建一辆新车，赋值）
C、查看老刘的小车信息（包括车牌号）； （根据名字查）
D、根据车牌号查找对应小车的信息

 

-------------------------------------------------car.sql
/*==============================================================*/
/* DBMS name:      ORACLE Version 11g                           */
/* Created on:     2018/12/3 10:03:55                           */
/*==============================================================*/


alter table carId
   drop constraint FK_CARID_RELATIONS_CAR;

alter table users
   drop constraint FK_USERS_RELATIONS_CARID;

drop table Car cascade constraints;

drop index Relationship_2_FK;

drop table carId cascade constraints;

drop index Relationship_1_FK;

drop table users cascade constraints;

/*==============================================================*/
/* Table: Car                                                   */
/*==============================================================*/
create table Car 
(
   c_id                 NUMBER(6)            not null,
   c_brand              VARCHAR2(12),
   c_model              VARCHAR2(12),
   c_color              VARCHAR2(8),
   c_price              NUMBER(8),
   constraint PK_CAR primary key (c_id)
);

/*==============================================================*/
/* Table: carId                                                 */
/*==============================================================*/
create table carId 
(
   i_id                 NUMBER(6)            not null,
   c_id                 NUMBER(6),
   i_card               VARCHAR2(10),
   i_type               VARCHAR2(8),
   i_texture            VARCHAR2(8),
   i_color              VARCHAR2(6),
   constraint PK_CARID primary key (i_id)
);

/*==============================================================*/
/* Index: Relationship_2_FK                                     */
/*==============================================================*/
create index Relationship_2_FK on carId (
   c_id ASC
);

/*==============================================================*/
/* Table: users                                                 */
/*==============================================================*/
create table users 
(
   u_id                 NUMBER(6)            not null,
   i_id                 NUMBER(6),
   u_name               VARCHAR2(8),
   constraint PK_USERS primary key (u_id)
);

/*==============================================================*/
/* Index: Relationship_1_FK                                     */
/*==============================================================*/
create index Relationship_1_FK on users (
   i_id ASC
);

alter table carId
   add constraint FK_CARID_RELATIONS_CAR foreign key (c_id)
      references Car (c_id);

alter table users
   add constraint FK_USERS_RELATIONS_CARID foreign key (i_id)
      references carId (i_id);

----------------------------------------------------------------Car.java
package com.jcl.pojo;

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


/**
 * The persistent class for the CAR database table.
 * 
 */
@Entity
@NamedQuery(name="Car.findAll", query="SELECT c FROM Car c")
public class Car implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name="C_ID")
    private long cId;

    @Column(name="C_BRAND")
    private String cBrand;

    @Column(name="C_COLOR")
    private String cColor;

    @Column(name="C_MODEL")
    private String cModel;

    @Column(name="C_PRICE")
    private BigDecimal cPrice;

    //bi-directional one-to-one association to Carid
    @OneToOne(mappedBy="car")
    private Carid carid;

    public Car() {
    }

    public long getCId() {
        return this.cId;
    }

    public void setCId(long cId) {
        this.cId = cId;
    }

    public String getCBrand() {
        return this.cBrand;
    }

    public void setCBrand(String cBrand) {
        this.cBrand = cBrand;
    }

    public String getCColor() {
        return this.cColor;
    }

    public void setCColor(String cColor) {
        this.cColor = cColor;
    }

    public String getCModel() {
        return this.cModel;
    }

    public void setCModel(String cModel) {
        this.cModel = cModel;
    }

    public BigDecimal getCPrice() {
        return this.cPrice;
    }

    public void setCPrice(BigDecimal cPrice) {
        this.cPrice = cPrice;
    }

    public Carid getCarid() {
        return this.carid;
    }

    public void setCarid(Carid carid) {
        this.carid = carid;
    }

    public Car(long cId, String cBrand, String cColor, String cModel, BigDecimal cPrice, Carid carid) {
        super();
        this.cId = cId;
        this.cBrand = cBrand;
        this.cColor = cColor;
        this.cModel = cModel;
        this.cPrice = cPrice;
        this.carid = carid;
    }
    public Car(long cId, String cBrand, String cColor, String cModel, BigDecimal cPrice) {
        super();
        this.cId = cId;
        this.cBrand = cBrand;
        this.cColor = cColor;
        this.cModel = cModel;
        this.cPrice = cPrice;
    }

    @Override
    public String toString() {
        return "Car [cId=" + cId + ", cBrand=" + cBrand + ", cColor=" + cColor + ", cModel=" + cModel + ", cPrice="
                + cPrice + "]";
    }

}
----------------------------------------------------------------Carid.java
package com.jcl.pojo;

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


/**
 * The persistent class for the CARID database table.
 * 
 */
@Entity
@NamedQuery(name="Carid.findAll", query="SELECT c FROM Carid c")
public class Carid implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @Column(name="I_ID")
    private long iId;

    @Column(name="I_CARD")
    private String iCard;

    @Column(name="I_COLOR")
    private String iColor;

    @Column(name="I_TEXTURE")
    private String iTexture;

    @Column(name="I_TYPE")
    private String iType;

    //bi-directional one-to-one association to Car
    @OneToOne
    @JoinColumn(name="C_ID")
    private Car car;

    //bi-directional one-to-one association to User
    @OneToOne(mappedBy="carid")
    private User user;

    public Carid() {
    }

    public long getIId() {
        return this.iId;
    }

    public void setIId(long iId) {
        this.iId = iId;
    }

    public String getICard() {
        return this.iCard;
    }

    public void setICard(String iCard) {
        this.iCard = iCard;
    }

    public String getIColor() {
        return this.iColor;
    }

    public void setIColor(String iColor) {
        this.iColor = iColor;
    }

    public String getITexture() {
        return this.iTexture;
    }

    public void setITexture(String iTexture) {
        this.iTexture = iTexture;
    }

    public String getIType() {
        return this.iType;
    }

    public void setIType(String iType) {
        this.iType = iType;
    }

    public Car getCar() {
        return this.car;
    }

    public void setCar(Car car) {
        this.car = car;
    }

    public User getUser() {
        return this.user;
    }

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

    @Override
    public String toString() {
        return "Carid [iId=" + iId + ", iCard=" + iCard + ", iColor=" + iColor + ", iTexture=" + iTexture + ", iType="
                + iType + ", car=" + car + "]";
    }

    public Carid(long iId, String iCard, String iColor, String iTexture, String iType, Car car, User user) {
        super();
        this.iId = iId;
        this.iCard = iCard;
        this.iColor = iColor;
        this.iTexture = iTexture;
        this.iType = iType;
        this.car = car;
        this.user = user;
    }
    public Carid(long iId, String iCard, String iColor, String iTexture, String iType, Car car) {
        super();
        this.iId = iId;
        this.iCard = iCard;
        this.iColor = iColor;
        this.iTexture = iTexture;
        this.iType = iType;
        this.car = car;
    }
}
----------------------------------------------------------------User.java
package com.jcl.pojo;

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


/**
 * The persistent class for the USERS database table.
 * 
 */
@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
    @Column(name="U_ID")
    private long uId;

    @Column(name="U_NAME")
    private String uName;

    //bi-directional one-to-one association to Carid
    @OneToOne
    @JoinColumn(name="I_ID")
    private Carid carid;

    public User() {
    }

    public long getUId() {
        return this.uId;
    }

    public void setUId(long uId) {
        this.uId = uId;
    }

    public String getUName() {
        return this.uName;
    }

    public void setUName(String uName) {
        this.uName = uName;
    }

    public Carid getCarid() {
        return this.carid;
    }

    public void setCarid(Carid carid) {
        this.carid = carid;
    }

    public User(long uId, String uName, Carid carid) {
        super();
        this.uId = uId;
        this.uName = uName;
        this.carid = carid;
    }

    @Override
    public String toString() {
        return "User [uId=" + uId + ", uName=" + uName + ", carid=" + carid + "]";
    }

}
---------------------------------------------------------------Demo.java
package com.jcl.test;

import java.math.BigDecimal;
import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;
import javax.persistence.Persistence;
import javax.swing.text.Caret;

import org.junit.After;
import org.junit.Before;
import org.junit.Ignore;
import org.junit.Test;

import com.jcl.pojo.Car;
import com.jcl.pojo.Carid;
import com.jcl.pojo.User;

public class Demo1 {
    EntityManager em;
    EntityTransaction tx ;
    EntityManagerFactory factory;
    private String jpql;
    @Before
    public void init(){
         factory = 
                Persistence.createEntityManagerFactory("HomeWork-JPQL");
         em = factory.createEntityManager();
         tx = em.getTransaction();
         tx.begin();
    }
    @After
    public void destroy(){
        tx.commit();
        if(em!=null){
            em.close();
        }
        if(factory!=null)
            factory.close();
    }
    /**
     *  A、老刘新买了一辆汽车，并且上了新车牌； （两个表中创建）
        B、老刘的小车被小偷偷走了，又买了一辆新车，但是车牌不变； （创建一辆新车，赋值）
        C、查看老刘的小车信息（包括车牌号）； （根据名字查）
        D、根据车牌号查找对应小车的信息

     * */
    //@Test
    @Ignore
    public void answerA(){
        try {
            Car car = new Car(000001l, "保时捷", "白色", "ccc", new BigDecimal(180000));
            Carid carid = new Carid(000001l, "京A-666", "白色", "民用", "铁", car);
            User user = new User(000001l, "老刘", carid);
            em.persist(car);
            em.persist(carid);
            em.persist(user);
        } catch (Exception e) {
            e.printStackTrace();
    }

        
    }
    //@Test
    @Ignore
    public void answerB(){
        try {
            //新买一辆车
            Car car = new Car(000002l, "宝马", "黑色", "ccc", new BigDecimal(260000));
            em.persist(car);
            //获取用户车牌号id
            jpql = "select u from User u where uName = ?0";
            User user = em.createQuery(jpql, User.class).setParameter(0, "老刘").getSingleResult();
            long iId = user.getCarid().getIId();
            //根据车牌号id修改车id
            Carid find = em.find(Carid.class, iId);
            find.setCar(car);
            em.persist(find);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    @Test
    //@Ignore
    public void answerC() {
        jpql = "select u from User u where uName = ?0";
        User user = em.createQuery(jpql, User.class).setParameter(0, "老刘").getSingleResult();
        long iId = user.getCarid().getIId();
        //根据车牌号id查找车id
        Carid carid = em.find(Carid.class, iId);
        long cid = carid.getCar().getCId();
        Car find = em.find(Car.class,cid);
        System.out.println(find);
        
    }
    @Test
    //@Ignore
    public  void answerD() {
        jpql ="select c from Carid c where iId = ?0";
         Carid carid = em.createQuery(jpql,Carid.class).setParameter(0,000001l).getSingleResult();
        System.out.println(carid);
    }
}