关于hibernate注解的简单应用
@Override
用途：重写父类的同名方法
单元测试注解
@Test
用途：用于测试
@Before
用途：单测方法走之前执行
@After
用途：单测方法走之后执行
注解的目标：替换小配置。替换hbm文件
@Entity :标识实体类（被持久化）
@Table ：DB层表的名称
@Transient ：不持久化某个属性
@Column：数据表中的字段名
@GenerateValue ：主键生成策略
-----------------关联-------------------------------------------------------------------------------------------------------
@OneToMany ：
@ManyToMany
@OneToOne
@JoinColumn
@JoinTable
Hibernate提供了Hibernate Annotations扩展包，使用注解完成映射。
在Hibernate3.3之前，需单独下载注解开发包。
配置持久化类
Hibernate注解可以代理hbm文件。
下面我们来用行动看看效果：
员工实体类:
package cn.curry.entity2;
import javax.persistence.*;
/**
* Created by Curry on 2017/2/16.
*/
@Entity
@Table(name = "Emp2")
public class Emp {
private Integer eid;
@Column
private String ename;
private Idcard idcard;
@OneToOne
@JoinColumn(name = "iid")
public Idcard getIdcard() {
return idcard;
}
public void setIdcard(Idcard idcard) {
this.idcard = idcard;
}
@Id
@GeneratedValue
public Integer getEid() {
return eid;
}
public void setEid(Integer eid) {
this.eid = eid;
}
public String getEname() {
return ename;
}
public void setEname(String ename) {
this.ename = ename;
}
}
身份实体类：
package cn.curry.entity2;
import javax.persistence.*;
/**
* Created by Curry on 2017/2/16.
*/
@Entity
@Table(name = "Idcard2")
public class Idcard {
@Id
@GeneratedValue
private Integer iid;
private String inum;
@OneToOne(mappedBy = "idcard",cascade = CascadeType.ALL)
private Emp emp;
public Integer getIid() {
return iid;
}
public void setIid(Integer iid) {
this.iid = iid;
}
public String getInum() {
return inum;
}
public void setInum(String inum) {
this.inum = inum;
}
public Emp getEmp() {
return emp;
}
public void setEmp(Emp emp) {
this.emp = emp;
}
}
下面我们看一下hibernate.cfg.xml文件
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<property name="connection.url">jdbc:oracle:thin:@localhost:1521:orcl</property>
<property name="connection.username">curry</property>
<property name="connection.password">curry</property>
<property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>
<property name="show_sql">true</property>
<property name="hbm2ddl.auto">update</property>
<!--和当前线程绑定 -->
<property name="current_session_context_class">thread</property>
<!--<mapping resource="cn/curry/entity/Grade.hbm.xml"/>
<mapping resource="cn/curry/entity/Student.hbm.xml"/>-->
<!-- 一对一-->
<mapping class="cn.curry.entity2.Emp"/>
<mapping class="cn.curry.entity2.Idcard"/>
<!-- 一对多双向关联-->
<mapping class="cn.curry.entity3.Emp"/>
<mapping class="cn.curry.entity3.Dept"/>
<!--多对多双向关联-->
<mapping class="cn.curry.entity4.Game"/>
<mapping class="cn.curry.entity4.Palyer"/>
</session-factory>
</hibernate-configuration>
下面我们在测试一下：
package cn.curry.test;
import cn.curry.entity2.Emp;import cn.curry.entity2.Idcard;import org.hibernate.Session;import org.hibernate.Transaction;import org.junit.After;import org.junit.Before;import org.junit.Test;/** * Created by Curry on 2017/2/16. */public class MyTest2 { Session session=null; Transaction tx; @Before public void before(){ session = HibernateUtil.currentSession(); tx=session.beginTransaction(); } @After public void after(){ tx.commit(); HibernateUtil.closeSession(); } @Test public void testOneToOne(){ Emp emp=new Emp(); emp.setEname("小明"); Idcard idcard=new Idcard(); idcard.setInum("88888888888"); idcard.setEmp(emp); emp.setIdcard(idcard); session.save(idcard); }}好了！看一下运行结果吧！
接下来我们再看一对多双向关联的配置
我们重新写一个例子，这次我们用员工和部门的列子来说；
首先还是先看实体类，注意看配置，看注解的书写，看每个属性的配置。
部门实体类：
package cn.curry.entity3;
import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;
/**
* Created by Curry on 2017/2/16.
*/
@Entity
@Table(name="Dept02")
public class Dept {
@Id
@GeneratedValue
private Integer did;
@Column
private String dname;
@OneToMany(mappedBy = "dept",cascade = CascadeType.ALL,fetch = FetchType.LAZY)
private Set<Emp> emps=new HashSet<Emp>();
public Integer getDid() {
return did;
}
public void setDid(Integer did) {
this.did = did;
}
public String getDname() {
return dname;
}
public void setDname(String dname) {
this.dname = dname;
}
public Set<Emp> getEmps() {
return emps;
}
public void setEmps(Set<Emp> emps) {
this.emps = emps;
}
}
员工实体类：
package cn.curry.entity3;
import javax.persistence.*;
/**
* Created by Curry on 2017/2/16.
*/
@Entity
@Table(name = "Emp02")
public class Emp {
@Id
@GeneratedValue
private Integer eid;
@Column
private String ename;
@ManyToOne
@JoinColumn(name="did")
private Dept dept;
public Integer getEid() {
return eid;
}
public void setEid(Integer eid) {
this.eid = eid;
}
public String getEname() {
return ename;
}
public void setEname(String ename) {
this.ename = ename;
}
public Dept getDept() {
return dept;
}
public void setDept(Dept dept) {
this.dept = dept;
}
}
hibernate.cfg.xml文件已经在前面写好了
下面我们看看测试类：
package cn.curry.test;
import cn.curry.entity3.Dept;
import cn.curry.entity3.Emp;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
/**
* Created by Curry on 2017/2/16.
*/
public class MyTest3 {
Session session=null;
Transaction tx;
@Before
public void before(){
session = HibernateUtil.currentSession();
tx=session.beginTransaction();
}
@After
public void after(){
tx.commit();
HibernateUtil.closeSession();
}
@Test
public void testOneToOne(){
Dept dept=new Dept();
dept.setDname("财务部");
Emp emp=new Emp();
emp.setEname("小明");
dept.getEmps().add(emp);
emp.setDept(dept);
session.save(dept);
}
@Test
public void select(){
Dept dept =session.get(Dept.class,3);
System.out.println(dept.getDname());
System.out.println(dept.getEmps().iterator().next().getEname());
}
}
我们来看一下结果：
好了，今天就先写这些例子。如果有什么问题可以交流。
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