spring嵌套对象@Embedded使用

最新推荐文章于 2025-07-10 14:31:59 发布

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#Embedded #AttributeOverrides

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本文介绍了Spring中@Embedded和@AttributeOverrides注解的使用，展示了如何将Employee类的EmployeePeriod对象嵌入到数据库中，并通过@AttributeOverrides改变字段在数据库中的映射名，从而实现数据的正确持久化。示例代码详细解释了这两个注解在实际操作中的应用。

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package com.demo.beans;

import javax.persistence.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.Embedded;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
@EntityListeners(MyMonitor.class)
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;

private String employeeName;

@Embedded
private EmployeePeriod employeePeriod;

public String getEmployeeName() {
return employeeName;
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public void setEmployeeName(String employeeName) {
this.employeeName = employeeName;
}

public EmployeePeriod getEmployeePeriod() {
return employeePeriod;
}

public void setEmployeePeriod(EmployeePeriod employeePeriod) {
this.employeePeriod = employeePeriod;
}

}

package com.demo.beans;

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Embeddable;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Embeddable
public class EmployeePeriod {
@Column(name="EmployeeStartDate")
@Temporal(TemporalType.DATE)
private Date startDate;

@Column(name="EmployeeEndDate")
@Temporal(TemporalType.DATE)
private Date endDate;

public Date getStartDate() {
return startDate;
}
public void setStartDate(Date startDate) {
this.startDate = startDate;
}
public Date getEndDate() {
return endDate;
}
public void setEndDate(Date endDate) {
this.endDate = endDate;
}

}

在持久化对象后，数据库中的表如下：

mysql> select * from employee;
+----+--------------+-----------------+-------------------+
| id | employeeName | EmployeeEndDate | EmployeeStartDate |
+----+--------------+-----------------+-------------------+
| 1| John Smith | 2015-02-13 | 2015-02-13 |
+----+--------------+-----------------+-------------------+

@AttributeOverrides的使用

修改上面的employee类

package com.demo.beans;

import javax.persistence.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.Embedded;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
@EntityListeners(MyMonitor.class)
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;

private String employeeName;

@Embedded
@AttributeOverrides({@AttributeOverride(name="startDate",column=@Column(name="begin")),
@AttributeOverride(name="endDate",column=@Column(name="end"))

}
)
private EmployeePeriod employeePeriod;

public String getEmployeeName() {
return employeeName;
}

public int getId() {
return id;
}

public void setId(int id) {
this.id = id;
}

public void setEmployeeName(String employeeName) {
this.employeeName = employeeName;
}

public EmployeePeriod getEmployeePeriod() {
return employeePeriod;
}

public void setEmployeePeriod(EmployeePeriod employeePeriod) {
this.employeePeriod = employeePeriod;
}

}

保存后的数据库中记录如下：

mysql> select * from employee;
+----+--------------+------------+------------+
| id | employeeName | end | begin |
+----+--------------+------------+------------+
| 1 | John Smith | 2015-02-13 | 2015-02-13 |
+----+--------------+------------+------------+
1 row in set (0.00 sec)