java序列号追加文件 java序列号怎么生成

JPA教程 - JPA ID序列生成器示例

我们可以使用序列为数据库中的实体生成id。

以下代码显示了如何使用序列来进行id生成。它首先使用SequenceGenerator从序列创建序列生成器，那么它在@GeneratedValue注释中标记序列生成器的名称。

@SequenceGenerator(name="Emp_Gen", sequenceName="Emp_Seq")
@Id @GeneratedValue(generator="Emp_Gen")
private int id;

例子

以下代码来自

Professor.java。package cn.w3cschool.common;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;
@Entity
public class Professor {
@SequenceGenerator(name="Emp_Gen", sequenceName="Emp_Seq")
@Id @GeneratedValue(generator="Emp_Gen")
private int id;
private String name;
private long salary;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public long getSalary() {
return salary;
}
public void setSalary(long salary) {
this.salary = salary;
}
public String toString() {
return "Employee id: " + getId() + " name: " + getName() + " salary: "
+ getSalary();
}
}

下面的代码来自

PersonDaoImpl.java。package cn.w3cschool.common;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import org.springframework.transaction.annotation.Transactional;
@Transactional
public class PersonDaoImpl {
public void test() {
Professor emp = new Professor();
emp.setName("name");
emp.setSalary(12345);
em.persist(emp);
}
@PersistenceContext
private EntityManager em;
}

以下代码来自

App.java。package cn.w3cschool.common;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class App {
public static void main(String[] args) {
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
"applicationContext.xml");
PersonDaoImpl dao = (PersonDaoImpl) context.getBean("personDao");
dao.test();
context.close();
Helper.checkData();
}
}下载 ID_SequenceGenerator.zip
以下是数据库表转储。Table Name: PROFESSOR
Row:
Column Name: ID,
Column Type: INTEGER:
Column Value: 1
Column Name: NAME,
Column Type: VARCHAR:
Column Value: name
Column Name: SALARY,
Column Type: BIGINT:
Column Value: 12345