标签：embeddedid idclass ssh
通过以前的文章，我们了解到@Table、@Column、@Id实现了单表的映射，并且书剑有一个@Id指定的唯一字段。有时我们的数据表也许是有多个主键联合组成的，因此对于单表映射的主键，还可以进行如下两种联合主键映射。======================================================================
（一）联合主键：使用@IdClass指定外部主键
步骤：以实现外部主键的引用。
package com.tgb.itoo.exam.entity;
import java.io.Serializable;
@SuppressWarnings("serial")
public class FamilyPK implements Serializable {
private String man;//丈夫
private String woman;//妻子
public String getMan() {
return man;
}
public void setMan(String man) {
this.man = man;
}
public String getWoman() {
return woman;
}
public void setWoman(String woman) {
this.woman = woman;
}
public FamilyPK() {
}
public FamilyPK(String man, String woman) {
this.man = man;
this.woman = woman;
}
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((man == null) ? 0 : man.hashCode());
result = prime * result + ((woman == null) ? 0 : woman.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
FamilyPK other = (FamilyPK) obj;
if (man == null) {
if (other.man != null)
return false;
} else if (!man.equals(other.man))
return false;
if (woman == null) {
if (other.woman != null)
return false;
} else if (!woman.equals(other.woman))
return false;
return true;
}
}
package com.tgb.itoo.exam.entity;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.Table;
@SuppressWarnings("serial")
@Entity
@Table(name="family")
@IdClass(FamilyPK.class)
public class Family implements Serializable {
private String man;// 丈夫
private String woman;// 棋子
private String address;// 地址
@Id
public String getMan() {
return man;
}
public void setMan(String man) {
this.man = man;
}
@Id
public String getWoman() {
return woman;
}
public void setWoman(String woman) {
this.woman = woman;
}
@Column(name="address" ,length=100)
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
package com.tgb.itoo.exam.service;
import javax.ejb.Remote;
import com.tgb.itoo.exam.entity.Family;
@Remote
public interface FamilyDAORemote {
// 新增
public boolean insert(Family family);
// 插入
public Family selectByPK(String man, String woman);
}
package com.tgb.itoo.exam.papermanage.serviceimpl;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import com.tgb.itoo.exam.entity.Family;
import com.tgb.itoo.exam.entity.FamilyPK;
import com.tgb.itoo.exam.service.FamilyDAORemote;
@Stateless
public class FamilyDAO implements FamilyDAORemote {
protected EntityManager em;
@Override
public boolean insert(Family family) {
try {
em.persist(family);
} catch (Exception e) {
e.printStackTrace();
return false;
}
return true;
}
@Override
public Family selectByPK(String man, String woman) {
FamilyPK epk = new FamilyPK(man, woman);
return em.find(Family.class, epk);
}
}
5）测试：客户端调用
package com.tgb.itoo.exam.papermanage.serviceimpl;
import java.util.Properties;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import com.tgb.itoo.exam.entity.Family;
import com.tgb.itoo.exam.service.FamilyDAORemote;
public class FamilyDAOClient {
public static void main(String[] args) throws NamingException {
//........
InitialContext ctx=new InitialContext();
FamilyDAORemote familyDAO=(FamilyDAORemote) ctx.lookup("FamilyDAO/remote");
//新增
Family family=new Family();
family.setMan("丈夫");
family.setWoman("妻子");
family.setAddress("地址");
familyDAO.insert(family);
//查询
Family family2=familyDAO.selectByPK("丈夫的名称", "妻子的名称");
System.out.println(family2.getAddress());
}
}
下文中将通过Demo演示《联合主键：使用@EmbeddedId嵌入外部主键》
持久化API（JPA）系列(七)实体关系映射(ORM)之单表映射@IdClass
标签：embeddedid idclass ssh
原文地址：http://blog.csdn.net/zhaolijing2012/article/details/45396151
