Hibernate映射之OneToOne(第二篇)

这是在项目中实际遇到的一个问题，纠结了很久。一开始参考mkyong的 ，两边都写OneToOne ，后来查看了一下项目经理在原来一些模块中的写法。 学习一下：

首先是E-R图：  一个货品可以进行多次调价。调价记录保存在productPrice表里面。

而Product表保存了最新一次调价的productPrice_id .第一次见这种表设计，感觉很怪。

 

 

 

Product类：

package net.myspring.blue.modules.crm.entity;



import javax.persistence.Cacheable;

import javax.persistence.Entity;

import javax.persistence.FetchType;

import javax.persistence.JoinColumn;

import javax.persistence.ManyToOne;

import javax.persistence.OneToOne;

import javax.persistence.Table;

import javax.persistence.Transient;



import org.junit.Ignore;



import net.myspring.blue.common.persistence.DataEntity;



@Entity

@Table(name="crm_product")

@Cacheable

public class Product extends DataEntity {

    private String name;

    private String namePinyin;

    private Brand brand;  //manyToOne

    private ProductPrice productPrice;

    private Long brandId;

    

    public String getName() {

        return name;

    }



    public void setName(String name) {

        this.name = name;

    }



    public String getNamePinyin() {

        return namePinyin;

    }



    public void setNamePinyin(String namePinyin) {

        this.namePinyin = namePinyin;

    }



    @ManyToOne(fetch = FetchType.LAZY)

    @JoinColumn(name = "brand_id")

    public Brand getBrand() {

        return brand;

    }



    public void setBrand(Brand brand) {

        this.brand = brand;

    }

    

    @Ignore

    @OneToOne(fetch=FetchType.LAZY)

    @JoinColumn(name="product_price_id")

    public ProductPrice getProductPrice() {

        return productPrice;

    }



    public void setProductPrice(ProductPrice productPrice) {

        this.productPrice = productPrice;

    }

    @Transient

    public Long getBrandId() {

        if(brandId==null && brand!=null) {

            brandId=brand.getId();

        }

        return brandId;

    }



    public void setBrandId(Long brandId) {

        this.brandId = brandId;

    }

    

}

 

 

ProductPrice类:

package net.myspring.blue.modules.crm.entity;



import java.math.BigDecimal;



import javax.persistence.Cacheable;

import javax.persistence.Entity;

import javax.persistence.FetchType;

import javax.persistence.JoinColumn;

import javax.persistence.ManyToOne;

import javax.persistence.Table;



import net.myspring.blue.common.persistence.DataEntity;



@Entity

@Table(name="crm_product_price")

@Cacheable

public class ProductPrice extends DataEntity{

    private BigDecimal oldPrice;

    private BigDecimal newPrice;

    private Product product; //ManyToOne

    

    public ProductPrice(BigDecimal oldPrice,BigDecimal newPrice,Product product){

        this.oldPrice=oldPrice;

        this.newPrice=newPrice;

        this.product=product;

    }

    public ProductPrice(){        

    }

    

    public BigDecimal getOldPrice() {

        return oldPrice;

    }



    public void setOldPrice(BigDecimal oldPrice) {

        this.oldPrice = oldPrice;

    }



    public BigDecimal getNewPrice() {

        return newPrice;

    }



    public void setNewPrice(BigDecimal newPrice) {

        this.newPrice = newPrice;

    }



    @ManyToOne(fetch=FetchType.LAZY)

    @JoinColumn(name="product_id")

    public Product getProduct() {

        return product;

    }



    public void setProduct(Product product) {

        this.product = product;

    }

    

}

注意Product和ProductPrice表之间的映射注解：
product.productPrice是这样的

　　@OneToOne(fetch=FetchType.LAZY)

    @JoinColumn(name="product_price_id")

    public ProductPrice getProductPrice() {

        return productPrice;

    }

 而productPrice.product是这样的：

　　@ManyToOne(fetch=FetchType.LAZY)

    @JoinColumn(name="product_id")

    public Product getProduct() {

        return product;

    }

持久化操作：

productPriceDao.save(productPrice); //先save  productPrice?有点看不懂

product.setProductPrice(productPrice); 

productDao.save(product);