mysql - 带有连接表的 ManyToOne、oneToMany

Question

我有这个例子，它有效，我只是想修改它，但我做不到。 这是示例的链接:example link 无论如何，我将其发布在这里:

这是实体的图片: Entity-Relation

 CREATE TABLE `stock` (
  `STOCK_ID` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
  `STOCK_CODE` VARCHAR(10) NOT NULL,
  `STOCK_NAME` VARCHAR(20) NOT NULL,
  PRIMARY KEY (`STOCK_ID`) USING BTREE,
  UNIQUE KEY `UNI_STOCK_NAME` (`STOCK_NAME`),
  UNIQUE KEY `UNI_STOCK_ID` (`STOCK_CODE`) USING BTREE
)

CREATE TABLE `category` (
  `CATEGORY_ID` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
  `NAME` VARCHAR(10) NOT NULL,
  `DESC` VARCHAR(255) NOT NULL,
  PRIMARY KEY (`CATEGORY_ID`) USING BTREE
)

CREATE TABLE  `stock_category` (
  `STOCK_ID` INT(10) UNSIGNED NOT NULL,
  `CATEGORY_ID` INT(10) UNSIGNED NOT NULL,
  `CREATED_DATE` DATE NOT NULL,
  `CREATED_BY` VARCHAR(10) NOT NULL,
  PRIMARY KEY (`STOCK_ID`,`CATEGORY_ID`),
  CONSTRAINT `FK_CATEGORY_ID` FOREIGN KEY (`CATEGORY_ID`) 
             REFERENCES `category` (`CATEGORY_ID`),
  CONSTRAINT `FK_STOCK_ID` FOREIGN KEY (`STOCK_ID`) 
             REFERENCES `stock` (`STOCK_ID`)
)

这里是 java 类: Stock.java

package com.mkyong.stock;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import static javax.persistence.GenerationType.IDENTITY;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.UniqueConstraint;

@Entity
@Table(name = "stock", catalog = "mkyongdb", uniqueConstraints = {
        @UniqueConstraint(columnNames = "STOCK_NAME"),
        @UniqueConstraint(columnNames = "STOCK_CODE") })
public class Stock implements java.io.Serializable {

    private Integer stockId;
    private String stockCode;
    private String stockName;
    private Set<StockCategory> stockCategories = new HashSet<StockCategory>(0);

    public Stock() {
    }

    public Stock(String stockCode, String stockName) {
        this.stockCode = stockCode;
        this.stockName = stockName;
    }

    public Stock(String stockCode, String stockName,
            Set<StockCategory> stockCategories) {
        this.stockCode = stockCode;
        this.stockName = stockName;
        this.stockCategories = stockCategories;
    }

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "STOCK_ID", unique = true, nullable = false)
    public Integer getStockId() {
        return this.stockId;
    }

    public void setStockId(Integer stockId) {
        this.stockId = stockId;
    }

    @Column(name = "STOCK_CODE", unique = true, nullable = false, length = 10)
    public String getStockCode() {
        return this.stockCode;
    }

    public void setStockCode(String stockCode) {
        this.stockCode = stockCode;
    }

    @Column(name = "STOCK_NAME", unique = true, nullable = false, length = 20)
    public String getStockName() {
        return this.stockName;
    }

    public void setStockName(String stockName) {
        this.stockName = stockName;
    }

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "pk.stock", cascade=CascadeType.ALL)
    public Set<StockCategory> getStockCategories() {
        return this.stockCategories;
    }

    public void setStockCategories(Set<StockCategory> stockCategories) {
        this.stockCategories = stockCategories;
    }

}

StockCategory.java

包 com.mkyong.stock;

import java.util.Date;

import javax.persistence.AssociationOverride;
import javax.persistence.AssociationOverrides;
import javax.persistence.Column;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;
import javax.persistence.JoinColumn;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Transient;

@Entity
@Table(name = "stock_category", catalog = "mkyongdb")
@AssociationOverrides({
        @AssociationOverride(name = "pk.stock", 
            joinColumns = @JoinColumn(name = "STOCK_ID")),
        @AssociationOverride(name = "pk.category", 
            joinColumns = @JoinColumn(name = "CATEGORY_ID")) })
public class StockCategory implements java.io.Serializable {

    private StockCategoryId pk = new StockCategoryId();
    private Date createdDate;
    private String createdBy;

    public StockCategory() {
    }

    @EmbeddedId
    public StockCategoryId getPk() {
        return pk;
    }

    public void setPk(StockCategoryId pk) {
        this.pk = pk;
    }

    @Transient
    public Stock getStock() {
        return getPk().getStock();
    }

    public void setStock(Stock stock) {
        getPk().setStock(stock);
    }

    @Transient
    public Category getCategory() {
        return getPk().getCategory();
    }

    public void setCategory(Category category) {
        getPk().setCategory(category);
    }

    @Temporal(TemporalType.DATE)
    @Column(name = "CREATED_DATE", nullable = false, length = 10)
    public Date getCreatedDate() {
        return this.createdDate;
    }

    public void setCreatedDate(Date createdDate) {
        this.createdDate = createdDate;
    }

    @Column(name = "CREATED_BY", nullable = false, length = 10)
    public String getCreatedBy() {
        return this.createdBy;
    }

    public void setCreatedBy(String createdBy) {
        this.createdBy = createdBy;
    }

    public boolean equals(Object o) {
        if (this == o)
            return true;
        if (o == null || getClass() != o.getClass())
            return false;

        StockCategory that = (StockCategory) o;

        if (getPk() != null ? !getPk().equals(that.getPk())
                : that.getPk() != null)
            return false;

        return true;
    }

    public int hashCode() {
        return (getPk() != null ? getPk().hashCode() : 0);
    }
}

Stockcategoryid.java

package com.mkyong.stock;

import javax.persistence.Embeddable;
import javax.persistence.ManyToOne;

@Embeddable
public class StockCategoryId implements java.io.Serializable {

    private Stock stock;
    private Category category;

    @ManyToOne
    public Stock getStock() {
        return stock;
    }

    public void setStock(Stock stock) {
        this.stock = stock;
    }

    @ManyToOne
    public Category getCategory() {
        return category;
    }

    public void setCategory(Category category) {
        this.category = category;
    }

    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        StockCategoryId that = (StockCategoryId) o;

        if (stock != null ? !stock.equals(that.stock) : that.stock != null) return false;
        if (category != null ? !category.equals(that.category) : that.category != null)
            return false;

        return true;
    }

    public int hashCode() {
        int result;
        result = (stock != null ? stock.hashCode() : 0);
        result = 31 * result + (category != null ? category.hashCode() : 0);
        return result;
    }

}

类别.java

package com.mkyong.stock;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import static javax.persistence.GenerationType.IDENTITY;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table(name = "category", catalog = "mkyongdb")
public class Category implements java.io.Serializable {

    private Integer categoryId;
    private String name;
    private String desc;
    private Set<StockCategory> stockCategories = new HashSet<StockCategory>(0);

    public Category() {
    }

    public Category(String name, String desc) {
        this.name = name;
        this.desc = desc;
    }

    public Category(String name, String desc, Set<StockCategory> stockCategories) {
        this.name = name;
        this.desc = desc;
        this.stockCategories = stockCategories;
    }

    @Id
    @GeneratedValue(strategy = IDENTITY)
    @Column(name = "CATEGORY_ID", unique = true, nullable = false)
    public Integer getCategoryId() {
        return this.categoryId;
    }

    public void setCategoryId(Integer categoryId) {
        this.categoryId = categoryId;
    }

    @Column(name = "NAME", nullable = false, length = 10)
    public String getName() {
        return this.name;
    }

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

    @Column(name = "[DESC]", nullable = false)
    public String getDesc() {
        return this.desc;
    }

    public void setDesc(String desc) {
        this.desc = desc;
    }

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "pk.category")
    public Set<StockCategory> getStockCategories() {
        return this.stockCategories;
    }

    public void setStockCategories(Set<StockCategory> stockCategories) {
        this.stockCategories = stockCategories;
    }

}

现在我希望股票只有一个类别，所以基本上我必须从 Stock.java 中的 @OneToMany 更改为 ManyToOne，但如果我只更改为它，则会出现错误。 有人可以帮助我吗？

应该是这样的:

@ManyToOne(fetch = FetchType.LAZY, mappedBy = "pk.stock", cascade=CascadeType.ALL)
private StockCategory stockgatery;

//setter and getter methods
//or something like
@ManyToOne
@JoinColumn(name="pk.stock"

但是我想不通。

Answer 1

尝试下面这样的事情......

@ManyToOne @JoinColumns({ @JoinColumn(name = "STOCK_ID", referencedColumnName = "STOCK_ID"), 
@JoinColumn(name = "CATEGORY_ID", referencedColumnName = "CATEGORY_ID") }) 
private StockCategory stockCategory;