hibernate注解

hibernate注解方式使我不需要在创建实体类的同时创建*.hbm.xml来映射数据库中对应表格，配置如下代码中所示：

Dept.java

package com.entity;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;
import javax.persistence.Transient;

@Entity
@Table(name="dept")
public class Dept implements java.io.Serializable {

// Fields

private Integer id;
private String name;
private String location;
private Set<Emp> emps = new HashSet<Emp>(0);

// Constructors

/** default constructor */
public Dept() {
}

/** full constructor */
public Dept(String name, String location, Set emps) {
this.name = name;
this.location = location;
this.emps = emps;
}

// Property accessors

@Id
@GeneratedValue(strategy=GenerationType.SEQUENCE,generator="seq_dept")
@SequenceGenerator(name="seq_dept",sequenceName="seq_dept_id",allocationSize=20,initialValue=1)
public Integer getId() {
return this.id;
}

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

@Column(name="name")
public String getName() {
return this.name;
}

public void setName(String name) {
this.name = name;
}

@Transient
public String getLocation() {
return this.location;
}

public void setLocation(String location) {
this.location = location;
}

@OneToMany(mappedBy="dept",cascade=CascadeType.ALL)
public Set<Emp> getEmps() {
return emps;
}

public void setEmps(Set<Emp> emps) {
this.emps = emps;
}

}

Emp.java

package com.entity;

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.NamedQuery;
import javax.persistence.SequenceGenerator;
import javax.persistence.Table;
import javax.persistence.Transient;

@Entity
@Table(name="emp")

public class Emp implements java.io.Serializable {

private Integer id;
private Dept dept;
private String name;
private String job;
private Double salary;

private Date hiredate;

// Constructors

/** default constructor */
public Emp() {
}

/** full constructor */
public Emp(Dept dept, String name, String job, Double salary) {
this.dept = dept;
this.name = name;
this.job = job;
this.salary = salary;
}

@Id
@GeneratedValue(strategy=GenerationType.SEQUENCE,generator="seq_emp")
@SequenceGenerator(name="seq_emp",sequenceName="seq_emp_eno",allocationSize=20,initialValue=1)
public Integer getId() {
return this.id;
}

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

@ManyToOne(fetch=FetchType.LAZY)
@JoinColumn(name="dept_id")
public Dept getDept() {
return this.dept;
}

public void setDept(Dept dept) {
this.dept = dept;
}

@Column(name="name")
public String getName() {
return this.name;
}

public void setName(String name) {
this.name = name;
}
@Transient
public String getJob() {
return this.job;
}

public void setJob(String job) {
this.job = job;
}
@Transient
public Double getSalary() {
return this.salary;
}

public void setSalary(Double salary) {
this.salary = salary;
}
@Column(name="hiredate")
public Date getHiredate() {
return hiredate;
}

public void setHiredate(Date hiredate) {
this.hiredate = hiredate;
}
}

hibernate.cfg.xml中的配置如下：

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>

<session-factory>
<property name="dialect">org.hibernate.dialect.PointbaseDialect</property>
<property name="connection.url">
jdbc:oracle:thin:@192.168.40.128:1521:orcl
</property>
<property name="connection.username">thunder</property>
<property name="connection.password">admin</property>
<property name="connection.driver_class">
oracle.jdbc.OracleDriver
</property>
<property name="myeclipse.connection.profile">thunder</property>
<property name="show_sql">true</property>
<property name="format_sql">true</property>
<mapping class="com.entity.Dept"/>
<mapping class="com.entity.Emp"/>
</session-factory>

</hibernate-configuration>

View Code
需要注意<mapping>中class属性值的引用方式，这是和引用*.hbm.xml的不同之处。

测试：

public static void main(String[] args) {
SessionFactory sf =null;
Session session=null;
Transaction tx=null;
try {

//新的获取sf的方式
sf=new AnnotationConfiguration().configure().buildSessionFactory();
//获得session
session =sf.openSession();
//获取事务
tx=session.beginTransaction();
Emp emp=new Emp();
emp.setName("神经一枚");
emp.setHiredate(new Date());
session.save(emp);
tx.commit();
System.out.println("add ok!");

//根据主键去查询信息，根据many-to-one加载部门信息
Emp emp=(Emp) session.load(Emp.class, new Integer(17));
System.out.println(emp.getName()+"    "+emp.getDept().getName());

//通过添加部门的同时把员工添加过去
Emp e1 =new Emp();
e1.setName("思过");
e1.setHiredate(new Date());

Dept d=new Dept();
d.setName("市场部");

d.getEmps().add(e1);
e1.setDept(d);
session.save(d);
tx.commit();
System.out.println("it is successful");

} catch (Exception e) {
//tx.rollback();
e.printStackTrace();
}finally{
session.close();
sf.close();
}

}

需要注意，获取Session工厂的方法与之前的不一样。

以上就是hibernate逐渐的简单使用。