EJB---->多表映射

实体的成员属性映射的字段分布在多张表中，如何处理？

本例子的实体MainTable具有四个成员属性：id、name、address和postcode。

其中与id和name映射的字段在MainTable表，与address和postcode属性映射的字段在Address表。

需要使用@javax.persistence.SecondaryTable注释和@Column.table()属性

import java.io.Serializable;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.Id;import javax.persistence.PrimaryKeyJoinColumn;import javax.persistence.SecondaryTable;@Entity// name 另一张表的表名 pkJoinColumns 另一张表的PK@SecondaryTable(name = "Address", pkJoinColumns = {@PrimaryKeyJoinColumn(name = "address_id")} )public class MainTable implements Serializable{private static final long serialVersionUID = 4016777473296175005L;private Integer id;// 主键private String name;// 姓名private String address;// 地址，该映射的字段分布在Address表private String postcode;// 邮编，该映射的字段分布在Address表    @Id     @GeneratedValuepublic Integer getId() {return id;}public void setId(Integer id) {this.id = id;}@Column(nullable=false,length=32)public String getName() {return name;}public void setName(String name) {this.name = name;}// 指定映射到表名为 Address 的表中@Column(table="Address")public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}// 指定映射到表名为 Address 的表中@Column(length=6, table="Address")public String getPostcode() {return postcode;}public void setPostcode(String postcode) {this.postcode = postcode;}    @Override    public int hashCode() {        int hash = 0;        hash += (this.id != null ? this.id.hashCode() : 0);        return hash;    }        @Override    public boolean equals(Object object) {        if (!(object instanceof MainTable)) {            return false;        }        MainTable other = (MainTable)object;        if (this.id != other.id && (this.id == null || !this.id.equals(other.id))) return false;        return true;    }    @Override    public String toString() {        return this.getClass().getName()+ "[id="+id+ ",name="+ name+ ",address="+ address+ ",postcode="+ postcode + "]";    }}