一.简介 1.You now have three methods for distinguishing references: Objects are identical if they occupy the same memory location in the JVM . This can be checked with the a == b operator. This concept is known as object identity. Objects are equal i…
一.介绍 1.这种引用方式不对,但删除时不能级联 要这种引用方式 2.The Bid class could be a problem. In object-oriented modeling, this is marked as a composition (the association between Item and Bid with the diamond). Thus, an Item is the owner of its Bid instances and holds a col…
一.结构 For example, you can map a class hierarchy to a single table, but, for a particular subclass, switch to a separate table with a foreign key–mapping strategy, just as with table-per-subclass. 二.代码 1. package org.jpwh.model.inheritance.mixed; impo…
一.结构 二.Hibernate支持的UserTypes接口 UserType —You can transform values by interacting with the plain JDBC PreparedStatement (when storing data) and ResultSet (when loading data).By implementing this interface, you can also control how Hibernate caches a…
一.结构 二.代码 1. package org.jpwh.model.advanced; import java.io.Serializable; import java.math.BigDecimal; import java.util.Currency; /* This value-typed class should be <code>java.io.Serializable</code>: When Hibernate stores entity instance dat…
一.简介 1. 2. 3. 4. to override this default mapping. The JPA specification has a convenient shortcut annotation for this purpose, @Lob @Entity public class Item { @Lob protected byte[] image; @Lob protected String description; // ... } This maps the by…
一.结构 The fourth option is to represent inheritance relationships as SQL foreign key associations. Every class/subclass that declares persistent properties—including abstract classes and even interfaces—has its own table.Unlike the table-per-concrete-…
一.结构 You can map an entire class hierarchy to a single table. This table includes columns for all properties of all classes in the hierarchy. The value of an extra type discriminator column or formula identifies the concrete subclass represented by a…
There are four different strategies for representing an inheritance hierarchy: Use one table per concrete class and default runtime polymorphic behavior. Use one table per concrete class but discard polymorphism and inheritance relationships comple…
Each @AttributeOverride for a component property is “complete”: any JPA or Hibernate annotation on the overridden property is ignored. This means the @Column annotations on the Address class are ignored—all BILLING_* columns are NULL able!(Bean Valid…
一.代码 1. package org.jpwh.model.inheritance.associations.onetomany; import org.jpwh.model.Constants; import javax.persistence.*; import javax.validation.constraints.NotNull; // Can not be @MappedSuperclass when it's a target class in associations! @En…
一.结构 二.代码 1. package org.jpwh.model.inheritance.associations.manytoone; import org.jpwh.model.Constants; import javax.persistence.*; import javax.validation.constraints.NotNull; // Can not be @MappedSuperclass when it's a target class in associations…
一.结构 A bag is an unordered collection that allows duplicate elements, like the java.util.Collection interface. Curiously, the Java Collections framework doesn’t include a bag implementation. You initialize the property with an ArrayList , andHibernat…
一.结构 二.model层 1. package org.jpwh.model.helloworld; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; /* Every persistent entity class must have at least th…
一.结构 二.配置文件约定 The JPA provider automatically picks up this descriptor if you place it in a META-INF /orm.xml file on the classpath of the persistence unit. If you prefer to use a different name or several files, you’ll have to change the configuratio…
