Hibernate注释中的参照完整性和复合主键类解析

在引入了或声明了相关表或类后就能够使用它下面的方法，例如：
（1）@Table(name = "bsp_corp_spl", catalog = "bspdb")
? （2）private BspCorpSplId id;
??? private BspCorp bspCorp;
因为要在dao类中使用HQL语句实现SELECT * FROM Table1 t1 WHERE t1.id.name=? AND t1.id.email=?
选出复合主键类的所有记录；所以要在类中实现get整体的方法，此时使用了复合主键类；
复合主键类给出实现equal，hashcode方法。
一、参照实体之间@OneToMany
??? 1、在被参照端的POJO类中注释：
@OneToMany(cascade=CascadeType.ALL, fetch=FetchType.LAZY, mappedBy="bspCorp")//单向的声明被参照类，联级在被参照端声明？

??? public Set<BspMySplContact> getBspMySplContacts() {
??????? return this.bspMySplContacts;
??? }
??? 2、参照端的注释：
?@ManyToOne(fetch = FetchType.LAZY)
??? @JoinColumn(name = "CORP_ID", nullable = false, insertable = false, updatable = false)//使用被参照类主键作为外键。
??? public BspCorp getBspCorp() {
??? ??? return this.bspCorp;
??? }


@AttributeOverrides由多个@AttributeOverride注释组成，每个@AttributeOverride表示属性的映射，它的定义如以下所示：

@Target({TYPE, METHOD, FIELD}) @Retention(RUNTIME)

public @interface AttributeOverride {

String name();

Column column();

}
二、复合主键实体类调用嵌套类：
在使用@AttributeOverride注释应注意以下几方面的问题：
1、了解嵌入类字段的含义
???? name属性表示被嵌入类中的属性名称。

??? column属性表示，对应所要嵌入的实体类的表，其中的name 为列字段的名称。

? 例如将tb_customer表中的customer_zip字段映射为Address嵌入类中的属性zip。代码如下所示：

@AttributeOverride(name = "zip",

column = @Column(name = "customer_zip")

)
2、嵌入类可以多次被引用
????? 使用嵌入式类的好处是：多个实体中都可以共享一个嵌入式类，方便了对实体的操作。
???????????????????????? 例如现在ContactEO也嵌入Address类，就很方便的映射为以下所示：

public class CustomerEO implements Serializable {
? ? ? ? ? private Integer id;
? ? ? ? ?? private String name;
? ? ? ? ? ? private String nickname;
????? ……getter和setter方法省略
? ? ? ? ? ? ? private Address address;
? @Embedded
? @AttributeOverrides( {

?????????????????? @AttributeOverride(name = "zip", column = @Column(name = "contact_zip")),

?????????????????? @AttributeOverride(name = "line1", column = @Column(name = "contact_line1")),

???????? })
?public Address getAddress() {

?????????????????? return address;
??? }

???????? public void setAddress(Address address) {

?????????????????? this.address = address;
?? }
}
三、实现复合主键嵌套类中的定义：
package com.bsp.entity;
import javax.persistence.Column;
import javax.persistence.Embeddable;
import org.hibernate.validator.Length;
import org.hibernate.validator.NotNull;
/**
?* BspCorpSplId entity.
?* @author Java Web2.0项目开发进阶宝典
?*/
@Embeddable
public class BspCorpSplId implements java.io.Serializable {
??? // 字段属性??
??? private String corpId;
??? private String spl;
??? ?/**默认构造器 */
??? public BspCorpSplId() {
??? }
??? @NotNull(message = "编号不能为空")
??? @Length(min = 1, max = 5, message = "编号长度应在1至5之间")
??? @Column(name = "CORP_ID", nullable = false, length = 5)
//因为在调用了嵌套类的实体类中已经将其初始化，所以此处的字段为已知
??? public String getCorpId() {
??? ??? return this.corpId;
??? }
??? public void setCorpId(String corpId) {
??? ??? this.corpId = corpId;
??? }
??? @Column(name = "SPL", nullable = false, length = 5)
??? public String getSpl() {
??? ??? return this.spl;
??? }
??? public void setSpl(String spl) {
??? ??? this.spl = spl;
??? }
??? public boolean equals(Object other) {//要实现的两个方法
??? ??? if ((this == other))
??? ??? ??? return true;
??? ??? if ((other == null))
??? ??? ??? return false;
??? ??? if (!(other instanceof BspCorpSplId))
??? ??? ??? return false;
??? ??? BspCorpSplId castOther = (BspCorpSplId) other;

??? ??? return ((this.getCorpId() == castOther.getCorpId()) || (this
??? ??? ??? ??? .getCorpId() != null
??? ??? ??? ??? && castOther.getCorpId() != null && this.getCorpId().equals(
??? ??? ??? ??? castOther.getCorpId())))
??? ??? ??? ??? && ((this.getSpl() == castOther.getSpl()) || (this.getSpl() != null
??? ??? ??? ??? ??? ??? && castOther.getSpl() != null && this.getSpl().equals(
??? ??? ??? ??? ??? ??? castOther.getSpl())));
??? }
??? public int hashCode() {
??? ??? int result = 17;

??? ??? result = 37 * result
??? ??? ??? ??? + (getCorpId() == null ? 0 : this.getCorpId().hashCode());
??? ??? result = 37 * result
??? ??? ??? ??? + (getSpl() == null ? 0 : this.getSpl().hashCode());
??? ??? return result;
??? }
}