Hibernate入门——员工信息查询

    Hibernate最主要的功能是将各种JDBC的操作以一种面向对象的方式封装起来，让开发者完全用面向对象的方式来操作数据库中的各种对象。在Hibernate中，一张数据表对应一个实体类，类中的属性对应表中的字段。把对表的各种操作抽象成一个会话（Session）类，将Session的一个实例与实体类的实例绑定。实体类实例中包含有数据表的一条数据，然后通过Session实例的save, delete, update, query 等操作就可以完成对数据库的操作了。

    下面写一个简单的例子，实现对数据库的查询。数据库使用Oracle中自带的表，scott用户下的EMP表和DEPT表。

 1、生成Session的类

package com.meng.hibernate; 
 
import org.hibernate.HibernateException; 
import org.hibernate.Session; 
import org.hibernate.SessionFactory; 
import org.hibernate.cfg.Configuration; 
 
public class HibernateSessionFactory { 
 
    private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml"; 
    private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>(); 
    private static Configuration configuration = new Configuration(); 
    private static SessionFactory sessionFactory; 
    private static String configFile = CONFIG_FILE_LOCATION; 
 
    static { 
        try { 
            configuration.configure(configFile); 
            sessionFactory = configuration.buildSessionFactory(); 
        } catch (Exception e) { 
            System.err.println("%%%% Error Creating SessionFactory %%%%"); 
            e.printStackTrace(); 
        } 
    } 
 
    private HibernateSessionFactory() { 
    } 
 
    public static Session getSession() throws HibernateException { 
        Session session = (Session) threadLocal.get(); 
        if (session == null || !session.isOpen()) { 
            if (sessionFactory == null) { 
                rebuildSessionFactory(); 
            } 
            session = (sessionFactory != null) ? sessionFactory.openSession() : null; 
            threadLocal.set(session); 
        } 
        return session; 
    } 
 
    public static void rebuildSessionFactory() { 
        try { 
            configuration.configure(configFile); 
            sessionFactory = configuration.buildSessionFactory(); 
        } catch (Exception e) { 
            System.err.println("%%%% Error Creating SessionFactory %%%%"); 
            e.printStackTrace(); 
        } 
    } 
 
    public static void closeSession() throws HibernateException { 
        Session session = (Session) threadLocal.get(); 
        threadLocal.set(null); 
 
        if (session != null) { 
            session.close(); 
        } 
    } 
 
    public static SessionFactory getSessionFactory() { 
        return sessionFactory; 
    } 
 
    public static void setConfigFile(String configFile) { 
        HibernateSessionFactory.configFile = configFile; 
        sessionFactory = null; 
    } 
 
    public static Configuration getConfiguration() { 
        return configuration; 
    } 
 
} 

 2、Employee实体类

package com.meng.po; 
 
import java.util.Date; 
import javax.persistence.CascadeType; 
import javax.persistence.Column; 
import javax.persistence.Entity; 
import javax.persistence.FetchType; 
import javax.persistence.Id; 
import javax.persistence.JoinColumn; 
import javax.persistence.ManyToOne; 
import javax.persistence.Table; 
 
@Entity 
@Table(name="EMP") 
public class Employee { 
    @Id 
    private int empno; 
    private String ename; 
    private String job; 
    private int mgr; 
    private Date hiredate; 
    private int sal; 
    private int comm; 
    @ManyToOne(cascade=CascadeType.ALL, fetch=FetchType.LAZY) 
    @JoinColumn(name="DEPTNO") 
    private Department dept; 
     
    public int getEmpno() { 
        return empno; 
    } 
    public void setEmpno(int empno) { 
        this.empno = empno; 
    } 
    public String getEname() { 
        return ename; 
    } 
    public void setEname(String ename) { 
        this.ename = ename; 
    } 
    public String getJob() { 
        return job; 
    } 
    public void setJob(String job) { 
        this.job = job; 
    } 
    public int getMgr() { 
        return mgr; 
    } 
    public void setMgr(int mgr) { 
        this.mgr = mgr; 
    } 
    public Date getHiredate() { 
        return hiredate; 
    } 
    public void setHiredate(Date hiredate) { 
        this.hiredate = hiredate; 
    } 
    public int getSal() { 
        return sal; 
    } 
    public void setSal(int sal) { 
        this.sal = sal; 
    } 
    public int getComm() { 
        return comm; 
    } 
    public void setComm(int comm) { 
        this.comm = comm; 
    } 
    public Department getDept() { 
        return dept; 
    } 
    public void setDept(Department dept) { 
        this.dept = dept; 
    } 
    @Override 
    public String toString() { 
        return "Employee [empno:" + empno + ", ename:" + ename + ", job:" + job + ", mgr:" + mgr + ", hiredate:" 
                + hiredate + ", sal:" + sal + ", comm:" + comm + ", \ndept:" + dept + "]"; 
    } 
} 

3、Department实体类

package com.meng.po; 
 
import javax.persistence.Column; 
import javax.persistence.Entity; 
import javax.persistence.Id; 
import javax.persistence.Table; 
 
@Entity 
@Table(name="DEPT") 
public class Department { 
    @Id 
    @Column(name="DEPTNO") 
    private int deptNo; 
    @Column(name="DNAME") 
    private String dName; 
    @Column(name="LOC") 
    private String location; 
 
    public int getDeptNo() { 
        return deptNo; 
    } 
    public void setDeptNo(int deptNo) { 
        this.deptNo = deptNo; 
    } 
    public String getdName() { 
        return dName; 
    } 
    public void setdName(String dName) { 
        this.dName = dName; 
    } 
    public String getLocation() { 
        return location; 
    } 
    public void setLocation(String location) { 
        this.location = location; 
    } 
    @Override 
    public String toString() { 
        return "Department [deptNo:" + deptNo + ", dName:" + dName + ", location:" + location + "]"; 
    } 
} 

4、测试类

package com.meng.test; 
 
import java.util.Iterator; 
import java.util.List; 
import org.hibernate.Query; 
import org.hibernate.Session; 
import com.meng.hibernate.HibernateSessionFactory; 
import com.meng.po.Employee; 
 
public class EmployeeQueryTest { 
    public static void main(String[] args){ 
        Session session = HibernateSessionFactory.getSession(); 
        Query query = session.createQuery("from Employee"); 
        List<Employee> employees = query.list(); 
        System.out.println("雇员信息："); 
        for(Employee employee : employees){ 
            System.out.println(employee); 
        } 
        HibernateSessionFactory.closeSession(); 
    } 
} 

5、Hibernate配置文件

<?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"> 
<hibernate-configuration> 
    <session-factory> 
        <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property> 
        <property name="hibernate.connection.password">tiger</property> 
        <property name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:EF35</property> 
        <property name="hibernate.connection.username">scott</property> 
        <property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property> 
        <property name="show_sql">true</property> 
         
        <mapping class="com.meng.po.Employee"/> 
        <mapping class="com.meng.po.Department"/> 
    </session-factory> 
</hibernate-configuration> 

将上面第9行的 EF35 改成你自己的数据库实例名。

6、项目中要使用到的Jar包

7、运行上面的 Test 文件，结果如下：

Hibernate: select employee0_.empno as empno0_, employee0_.comm as comm0_, employee0_.DEPTNO as DEPTNO0_, employee0_.ename as ename0_, employee0_.hiredate as hiredate0_, employee0_.job as job0_, employee0_.mgr as mgr0_, employee0_.sal as sal0_ from EMP employee0_ 
雇员信息： 
Hibernate: select department0_.DEPTNO as DEPTNO1_0_, department0_.DNAME as DNAME1_0_, department0_.LOC as LOC1_0_ from DEPT department0_ where department0_.DEPTNO=? 
Employee [empno:7369, ename:SMITH, job:CLERK, mgr:7902, hiredate:1980-12-17 00:00:00.0, sal:800, comm:0,  
dept:Department [deptNo:20, dName:RESEARCH, location:DALLAS]] 
Hibernate: select department0_.DEPTNO as DEPTNO1_0_, department0_.DNAME as DNAME1_0_, department0_.LOC as LOC1_0_ from DEPT department0_ where department0_.DEPTNO=? 
Employee [empno:7499, ename:ALLEN, job:SALESMAN, mgr:7698, hiredate:1981-02-20 00:00:00.0, sal:1600, comm:300,  
dept:Department [deptNo:30, dName:SALES, location:CHICAGO]] 
Employee [empno:7521, ename:WARD, job:SALESMAN, mgr:7698, hiredate:1981-02-22 00:00:00.0, sal:1250, comm:500,  
dept:Department [deptNo:30, dName:SALES, location:CHICAGO]] 
Employee [empno:7566, ename:JONES, job:MANAGER, mgr:7839, hiredate:1981-04-02 00:00:00.0, sal:2975, comm:0,  
dept:Department [deptNo:20, dName:RESEARCH, location:DALLAS]] 
Employee [empno:7654, ename:MARTIN, job:SALESMAN, mgr:7698, hiredate:1981-09-28 00:00:00.0, sal:1250, comm:1400,  
dept:Department [deptNo:30, dName:SALES, location:CHICAGO]] 
Employee [empno:7698, ename:BLAKE, job:MANAGER, mgr:7839, hiredate:1981-05-01 00:00:00.0, sal:2850, comm:0,  
dept:Department [deptNo:30, dName:SALES, location:CHICAGO]] 
Hibernate: select department0_.DEPTNO as DEPTNO1_0_, department0_.DNAME as DNAME1_0_, department0_.LOC as LOC1_0_ from DEPT department0_ where department0_.DEPTNO=? 
Employee [empno:7782, ename:CLARK, job:MANAGER, mgr:7839, hiredate:1981-06-09 00:00:00.0, sal:2450, comm:0,  
dept:Department [deptNo:10, dName:ACCOUNTING, location:NEW YORK]] 
Employee [empno:7788, ename:SCOTT, job:ANALYST, mgr:7566, hiredate:1987-04-19 00:00:00.0, sal:3000, comm:0,  
dept:Department [deptNo:20, dName:RESEARCH, location:DALLAS]] 
Employee [empno:7839, ename:KING, job:PRESIDENT, mgr:0, hiredate:1981-11-17 00:00:00.0, sal:5000, comm:0,  
dept:Department [deptNo:10, dName:ACCOUNTING, location:NEW YORK]] 
Employee [empno:7844, ename:TURNER, job:SALESMAN, mgr:7698, hiredate:1981-09-08 00:00:00.0, sal:1500, comm:0,  
dept:Department [deptNo:30, dName:SALES, location:CHICAGO]] 
Employee [empno:7876, ename:ADAMS, job:CLERK, mgr:7788, hiredate:1987-05-23 00:00:00.0, sal:1100, comm:0,  
dept:Department [deptNo:20, dName:RESEARCH, location:DALLAS]] 
Employee [empno:7900, ename:JAMES, job:CLERK, mgr:7698, hiredate:1981-12-03 00:00:00.0, sal:950, comm:0,  
dept:Department [deptNo:30, dName:SALES, location:CHICAGO]] 
Employee [empno:7902, ename:FORD, job:ANALYST, mgr:7566, hiredate:1981-12-03 00:00:00.0, sal:3000, comm:0,  
dept:Department [deptNo:20, dName:RESEARCH, location:DALLAS]] 
Employee [empno:7934, ename:MILLER, job:CLERK, mgr:7782, hiredate:1982-01-23 00:00:00.0, sal:1300, comm:0,  
dept:Department [deptNo:10, dName:ACCOUNTING, location:NEW YORK]] 

下面的源码因为大小限制，将其依赖的Jar包删除了，请亲们自行在项目中添加。