Eclipse + JBoss 5 + EJB3 Development Guide (8)

Implement One-to-many (One-to-many) mappings for entity beans

EJB3 's One-to-many mappings are set using @onetomany, and if it is a two-way one-to-many mapping, the @manytoone setting is required on the many side. Given two tables in this book, the other table t_customers in the previous article, and the structure of the other table is shown in Figure 1.

Figure 1 T_orders Table

T_customers and T_orders tables are a one-to-many relationship, a customer may have multiple order, and an order can only have one customer.

You need to define a property of a collection type in the customer class to hold multiple order objects, and the customer class code is as follows:

Package entity;

Import java.util.Collection;

Import Javax.persistence.CascadeType;

Import javax.persistence.Entity;

Import Javax.persistence.FetchType;

Import Javax.persistence.GeneratedValue;

Import Javax.persistence.GenerationType;

Import Javax.persistence.Id;

Import Javax.persistence.JoinColumn;

Import javax.persistence.JoinTable;

Import Javax.persistence.ManyToMany;

Import Javax.persistence.OneToMany;

Import Javax.persistence.OneToOne;

Import Javax.persistence.PrimaryKeyJoinColumn;

Import javax.persistence.Table;

　　　 @Entity @Table (name = "T_customers") public class Customer {private int id;

　　　 private String name;

　　　 Private referee Referee;

　　　 Private collection<order> orders;

　　　　　　　 @OneToMany (Mappedby = "Customer", cascade = cascadetype.all) public collection<order> getorders () {

　　　 return orders;

　　　 public void Setorders (collection<order> orders) {this.orders = orders; } @Id @GeneRatedvalue (strategy = generationtype.identity) public int getId () {return id; } 　　　 ... ... }