下面使用hibernate的API中说明的三种方式来定义主键，主要使用Annotation来定义hibernate中的联合主键
下面取至hibernate的API文档：
定义组合主键的几种语法：
1、将组件类注解为@Embeddable，并将组件的属性注解为@Id
2、将组件的属性注解为@EmbeddedId
3、将类注解为@IdClass，并将该实体中所有属于主键的属性都注解为@Id
下面就分别使用这三种方式来定义联合主键。
建表的SQL语句：
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CREATE TABLE `syslogs` (
`id` varchar(50) NOT NULL,
`yhid` varchar(50) NOT NULL,
`modelname` varchar(100) DEFAULT NULL,
`content` varchar(500) DEFAULT NULL,
`inserttime` varchar(20) DEFAULT NULL,
`remark` varchar(50) DEFAULT NULL,
PRIMARY KEY (`id`,`yhid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf-8;
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一、将组件类注解为@Embeddable
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/**
* SysLogsDtoId代表主键类
*/
package com.hibernate.dto;
import javax.persistence.Embeddable;
/**
* 1、主键类必须要实现java.io.Serializable接口
* 2、主键类必须要重写equals和hashCode方法
* @author ibm
*/
@Embeddable
public class SysLogsDtoId implements java.io.Serializable {
private static final long serialVersionUID = 1L;
private String id;
private String yhid;
public SysLogsDtoId() {
}
public SysLogsDtoId(String id, String yhid) {
this.id = id;
this.yhid = yhid;
}
public String getId() {
return this.id;
}
public void setId(String id) {
this.id = id;
}
public String getYhid() {
return this.yhid;
}
public void setYhid(String yhid) {
this.yhid = yhid;
}
public boolean equals(Object other) {
if ((this == other))
return true;
if ((other == null))
return false;
if (!(other instanceof SysLogsDtoId))
return false;
SysLogsDtoId castOther = (SysLogsDtoId) other;
return ((this.getId() == castOther.getId()) || (this.getId() != null && castOther.getId() != null && this.getId().equals(castOther.getId())))
&& ((this.getYhid() == castOther.getYhid()) || (this.getYhid() != null && castOther.getYhid() != null && this.getYhid().equals(
castOther.getYhid())));
}
public int hashCode() {
int result = 17;
result = 37 * result + (getId() == null ? 0 : this.getId().hashCode());
result = 37 * result + (getYhid() == null ? 0 : this.getYhid().hashCode());
return result;
}
}
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/**
* SysLogsDto为表对象映射类，其中主键为主键类SysLogsDtoId
*/
package com.hibernate.dto;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name = "syslogs")
public class SysLogsDto implements java.io.Serializable {
private static final long serialVersionUID = 1L;
private SysLogsDtoId id;
private String modelname;
private String content;
private String inserttime;
private String remark;
public SysLogsDto() {
}
public SysLogsDto(SysLogsDtoId id) {
this.id = id;
}
public SysLogsDto(SysLogsDtoId id, String modelname, String content, String inserttime, String remark) {
this.id = id;
this.modelname = modelname;
this.content = content;
this.inserttime = inserttime;
this.remark = remark;
}
@Id
public SysLogsDtoId getId() {
return this.id;
}
public void setId(SysLogsDtoId id) {
this.id = id;
}
@Column(name = "modelname", length = 100)
public String getModelname() {
return this.modelname;
}
public void setModelname(String modelname) {
this.modelname = modelname;
}
@Column(name = "content", length = 500)
public String getContent() {
return this.content;
}
public void setContent(String content) {
this.content = content;
}
@Column(name = "inserttime", length = 20)
public String getInserttime() {
return this.inserttime;
}
public void setInserttime(String inserttime) {
this.inserttime = inserttime;
}
@Column(name = "remark", length = 50)
public String getRemark() {
return this.remark;
}
public void setRemark(String remark) {
this.remark = remark;
}
}
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二、将组件的属性注解为@EmbeddedId
这种情况最简单，主键类只用定义主键字段，不需要写任何注解。然后在对象类中在主键类的get方法上加上@EmbeddedId注解。
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/**
* SysLogsDtoId代表主键类
*/
package com.hibernate.dto;
public class SysLogsDtoId implements java.io.Serializable {
private static final long serialVersionUID = 1L;
private String id;
private String yhid;
public SysLogsDtoId() {
}
public SysLogsDtoId(String id, String yhid) {
this.id = id;
this.yhid = yhid;
}
public String getId() {
return this.id;
}
public void setId(String id) {
this.id = id;
}
public String getYhid() {
return this.yhid;
}
public void setYhid(String yhid) {
this.yhid = yhid;
}
public boolean equals(Object other) {
if ((this == other))
return true;
if ((other == null))
return false;
if (!(other instanceof SysLogsDtoId))
return false;
SysLogsDtoId castOther = (SysLogsDtoId) other;
return ((this.getId() == castOther.getId()) || (this.getId() != null && castOther.getId() != null && this.getId().equals(castOther.getId())))
&& ((this.getYhid() == castOther.getYhid()) || (this.getYhid() != null && castOther.getYhid() != null && this.getYhid().equals(
castOther.getYhid())));
}
public int hashCode() {
int result = 17;
result = 37 * result + (getId() == null ? 0 : this.getId().hashCode());
result = 37 * result + (getYhid() == null ? 0 : this.getYhid().hashCode());
return result;
}
}
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/**
* SysLogsDto为表对象映射类，其中主键为主键类SysLogsDtoId
*/
package com.hibernate.dto;
import javax.persistence.Column;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;
import javax.persistence.Table;
@Entity
@Table(name = "syslogs")
public class SysLogsDto implements java.io.Serializable {
private static final long serialVersionUID = 1L;
private SysLogsDtoId id;
private String modelname;
private String content;
private String inserttime;
private String remark;
public SysLogsDto() {
}
public SysLogsDto(SysLogsDtoId id) {
this.id = id;
}
public SysLogsDto(SysLogsDtoId id, String modelname, String content, String inserttime, String remark) {
this.id = id;
this.modelname = modelname;
this.content = content;
this.inserttime = inserttime;
this.remark = remark;
}
@EmbeddedId
public SysLogsDtoId getId() {
return this.id;
}
public void setId(SysLogsDtoId id) {
this.id = id;
}
@Column(name = "modelname", length = 100)
public String getModelname() {
return this.modelname;
}
public void setModelname(String modelname) {
this.modelname = modelname;
}
@Column(name = "content", length = 500)
public String getContent() {
return this.content;
}
public void setContent(String content) {
this.content = content;
}
@Column(name = "inserttime", length = 20)
public String getInserttime() {
return this.inserttime;
}
public void setInserttime(String inserttime) {
this.inserttime = inserttime;
}
@Column(name = "remark", length = 50)
public String getRemark() {
return this.remark;
}
public void setRemark(String remark) {
this.remark = remark;
}
}
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三、将类注解为@IdClass，并将该实体中所有属于主键的属性都注解为@Id
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/**
* SysLogsDtoId代表主键类
*/
package com.hibernate.dto;
public class SysLogsDtoId implements java.io.Serializable {
private static final long serialVersionUID = 1L;
private String id;
private String yhid;
public SysLogsDtoId() {
}
public SysLogsDtoId(String id, String yhid) {
this.id = id;
this.yhid = yhid;
}
public String getId() {
return this.id;
}
public void setId(String id) {
this.id = id;
}
public String getYhid() {
return this.yhid;
}
public void setYhid(String yhid) {
this.yhid = yhid;
}
public boolean equals(Object other) {
if ((this == other))
return true;
if ((other == null))
return false;
if (!(other instanceof SysLogsDtoId))
return false;
SysLogsDtoId castOther = (SysLogsDtoId) other;
return ((this.getId() == castOther.getId()) || (this.getId() != null && castOther.getId() != null && this.getId().equals(castOther.getId())))
&& ((this.getYhid() == castOther.getYhid()) || (this.getYhid() != null && castOther.getYhid() != null && this.getYhid().equals(
castOther.getYhid())));
}
public int hashCode() {
int result = 17;
result = 37 * result + (getId() == null ? 0 : this.getId().hashCode());
result = 37 * result + (getYhid() == null ? 0 : this.getYhid().hashCode());
return result;
}
}
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/**
* SysLogsDto为表对象映射类，其中主键为主键类SysLogsDtoId
*/
package com.hibernate.dto;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.Table;
@Entity
@Table(name = "syslogs")
@IdClass(value=SysLogsDtoId.class)
public class SysLogsDto implements java.io.Serializable {
private static final long serialVersionUID = 1L;
private String id;
private String yhid;
private String modelname;
private String content;
private String inserttime;
private String remark;
public SysLogsDto() {
}
@Id
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
@Id
public String getYhid() {
return yhid;
}
public void setYhid(String yhid) {
this.yhid = yhid;
}
@Column(name = "modelname", length = 100)
public String getModelname() {
return this.modelname;
}
public void setModelname(String modelname) {
this.modelname = modelname;
}
@Column(name = "content", length = 500)
public String getContent() {
return this.content;
}
public void setContent(String content) {
this.content = content;
}
@Column(name = "inserttime", length = 20)
public String getInserttime() {
return this.inserttime;
}
public void setInserttime(String inserttime) {
this.inserttime = inserttime;
}
@Column(name = "remark", length = 50)
public String getRemark() {
return this.remark;
}
public void setRemark(String remark) {
this.remark = remark;
}
}
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原文链接：http://blog.csdn.net/wyc_cs/article/details/9031991