[英]jpa entity mapping couple tables
我有用于JSON解析的实体
@Entity
public class Product{
private int productId;
private String productName;
private BigDecimal productPrice;
private int productVendorId;
private String productVendorName;
private int productCategoryId;
private String productCategoryName;
//getters setters here
在数据库中创建了3个表:产品(product_id,product_name,product_price,product_vendor_id),product_category_id); 供应商(vendor_id,vendor_name); 类别(category_id,category_name); 在第一张表product_vendor_id fk->卖方中的vendor_id pk和product_category_id fk-> category中的category_id pk中,我尝试了以下操作:
@Entity
@Table(name = "products, schema = "market")
public class Product
@Id
@Column(updatable = false, nullable = false, name = "product_id")
private int Id;
@Column(name = "product_name")
private String productName;
@Column(name = "product_price")
private BigDecimal productPrice;
@Column(name = "product_vendor_id")
private int productVendorId;
@Columnt(table = "vendors", name = "vendor_name")
private String vendor_name;
@Column(name = "product_category_id")
private int productCategoryId;
@Column(table = "categories", name = "category_name")
private String productCategorName;
//getters setters here
收到很多错误:例如我在产品表等中没有category_name列。使用时收到此错误
@Table(name = "products", schema = "market" )
@SecondaryTables({@SecondaryTable(name = "vendors", schema = "market"),
@SecondaryTable(name = "categories", schema = "market")})
@JsonIgnoreProperties(ignoreUnknown = true)
public class Product {
....
@JoinColumn(name = "product_vendor_id", referencedColumnName = "vendor_id")
private int productVendorID;
@JoinColumn(table = "vendors", name = "vendor_name")
private String productVendorName;
@JoinColumn(name = "product_category_id", referencedColumnName =
"product_category_id")
private int productCategoryID;
@JoinColumn(table = "categories", name = "category_name")
private String productCategoryName;
例外:
Caused by: org.postgresql.util.PSQLException: ERROR: column
product0_1_.product_id doesn't exist
Hint: There may have been a link to the "product0_.product_id" column
Position: 705
如何在3个表上映射此实体? upd:我不想分离这个实体,我也需要这个来反序列化我的json对象,只想在不同的操作上重用这个实体。 json的例子
{"productID":"1111111","productName":"Cool product","productPrice":"99.99","productVendorName":"Some store","productVendorID":"1337","productCategoryName":"Food","productCategoryID":"1"}
由于存在3个单独的表,因此您需要创建三个单独的实体类。 我还假设供应商和类别表与产品具有一对多的关系。 试试下面的代码:
产品名称 :
@Entity
public class Product {
@Id
private int productId;
private String productName;
private BigDecimal productPrice;
private String productVendorName;
private String productCategoryName;
@ManyToOne
@JoinColumn(name = "productCategoryId")
private Category category;
@ManyToOne
@JoinColumn(name = "productVendorId")
private Vendors vendor;
}
分类 :
@Entity
public class Category {
@Id
private Integer categoryId;
private String categoryName;
@OneToMany(mappedBy = "category", cascade = CascadeType.ALL, fetch = FetchType.LAZY, orphanRemoval = true)
@NotEmpty
private List<Product> products = new ArrayList<>();
}
供应商:
@Entity
public class Vendors {
@Id
private int vendorId;
private String vendorName;
@OneToMany(mappedBy = "vendor", cascade = CascadeType.ALL, fetch = FetchType.LAZY, orphanRemoval = true)
@NotEmpty
private List<Product> products = new ArrayList<>();
}
不过,我建议您使用上述方法,如果您仍然希望拥有单个实体类和3个带有冗余数据的单独表,请使用以下方法:
@Entity
@SecondaryTables({ @SecondaryTable(name = "vendors"), @SecondaryTable(name = "categories") })
public class Product {
@Id
private int productId;
private String productName;
private BigDecimal productPrice;
private String productVendorName;
private String productCategoryName;
@Column(table = "categories")
private Integer categoryId;
@Column(table = "categories")
private String categoryName;
@Column(table = "vendors")
private int vendorId;
@Column(table = "vendors")
private String vendorName;
}
主表的id列将出现在所有3个表中,并用于连接它们。
很抱歉这个问题的措辞不好,只是不知道该如何改写我想要的东西。 我所需要的全部只是为产品表中没有的字段添加@transient注释,并像建议的答案一样将其分开。
@Entity
@Table(name = "products", schema = "store" )
@JsonIgnoreProperties(ignoreUnknown = true)
public class Product {
@Id
@Column(updatable = false, nullable = false, name = "product_id")
private int productId;
@Column(name = "product_name")
private String productName;
@Column(name = "product_price")
private BigDecimal productPrice;
@Transient
private String productVendorName;
@Transient
private String productCategoryName;
@Transient
private int vendorId;
@Transient
private int categoryId;
@ManyToOne
@JoinColumn(name = "product_category_id")
private Category category;
@ManyToOne
@JoinColumn(name = "product_vendor_id")
private Vendor vendor;
}
供应商表实体
@Entity
@Table(name = "vendors", schema = "store")
public class Vendor {
@Id
@Column(name = "vendor_id")
private int vendorId;
@Column(name = "vendor_name")
private String vendorName;
@OneToMany(mappedBy = "vendor", cascade = CascadeType.ALL, fetch = FetchType.LAZY,
orphanRemoval = true)
@NotNull
private List<Product> products = new ArrayList<>();
}
和类别
@Entity
@Table(name = "categories", schema = "store")
public class Category {
@Id
@Column(name = "category_id")
private Integer categoryId;
@Column(name = "category_name")
private String categoryName;
@OneToMany(mappedBy = "category", cascade = CascadeType.ALL, fetch = FetchType.LAZY,
orphanRemoval = true)
@NotNull
private List<Product> products = new ArrayList<>();
}
想要在这里留下我的问题的完整答案,也许以后有人需要它。只需检查toString的一些问题即可。 仅在Product.class中使用它,最好制作两个版本的print json和jpa。
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