java框架Hibernate入门

作者: _琳哥 | 来源:发表于2017-11-20 11:43 被阅读10次

针对版本hibernate-distribution-3.6.0.Final的学习

搭建环境及开发步骤

引入jar包
- hibernate3.jar核心
- required 必须引入的(6个)
  - antlr-2.7.6.jar
  - commons-collections-3.1.jar
  - dom4j-1.6.1.jar
  - javassist-3.12.0.GA.jar
  - jta-1.1.jar
  - slf4j-api-1.6.1.jar
- jpa 目录
  - hibernate-jpa-2.0-api-1.0.0.Final.jar
- 数据库驱动包
  - mysql-connector-java-5.1.7-bin.jar
写对象以及对象的映射
- Employee.java 对象
- Employee.hbm.xml 对象的映射 (映射文件)

public class Employee {

    private int empId;
    private String empName;
    private Date workDate;

    public int getEmpId(){
        return empId;
    }

    public void setEmpId(int empId){
        this.empId = empId;
    }

    public String getEmpName(){
        return empName;
    }

    public void setEmpName(String empName){
        this.empName = empName;
    }

    public Date getWorkDate(){
        return workDate;
    }

    public void setWorkDate(Date workDate){
        this.workDate = workDate;
    }

    @Override
    public String toString(){
        return "Employee{" +
                "empId=" + empId +
                ", empName='" + empName + '\'' +
                ", workDate=" + workDate +
                '}';
    }
}

Employee.hbm.xml文件 : 先确保数据库和表都已存在

create table employee (id int not null primary key auto_increment,empName varchar(10),workDate datetime);

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<!-- Generated Nov 9, 2006 6:27:53 PM by Hibernate Tools 3.2.0.beta7 -->
<hibernate-mapping package="com.flynn">
    <class name="Employee" table="employee" >
        <!--主键-->
        <id name="empId" column="id" type="java.lang.Integer">
            <generator class="native"/>
        </id>
        <property name="empName" column="empName"></property>
        <property name="workDate" column="workDate"></property>
    </class>
</hibernate-mapping>

src/hibernate.cfg.xml 主配置文件
- 数据库连接配置
- 加载所用的映射(*.hbm.xml)

<!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>
        <!--数据库连接-->
        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="hibernate.connection.url">jdbc:mysql://192.168.5.129:3306/partner</property>
        <property name="hibernate.connection.username">root</property>
        <property name="hibernate.connection.password">mysql</property>
        <property name="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</property>

        <property name="hibernate.show_sql">true</property>

        <mapping resource="com/flynn/Employee.hbm.xml"></mapping>
    </session-factory>
</hibernate-configuration>

4.App.java测试 : 一次简单的测试

public class App {

    @Test
    public void testSave() throws Exception{
        Employee emp = new Employee();
        emp.setEmpName("zhang");
        emp.setWorkDate(new Date());
        // 获取加载配置文件的管理类对象
        Configuration config = new Configuration();
        // 加载配置文件
        config.configure();
        SessionFactory sessionFactory = config.buildSessionFactory();
        // 创建session
        Session session = sessionFactory.openSession();
        // 提交事务
        Transaction tx = session.beginTransaction();
        // --执行操作--
        session.save(emp);
        // 提交事务
        tx.commit();
        // 关闭session
        session.close();
    }
}

测试通过 :

testSave.png

Hibernate的Api

Configuration 配置管理类对象
- config.configure(); 加载主配置文件的方法(hibernate.cfg.xml) 默认加载src/hibernate.cfg.xml
- config.configure(“cn/config/hibernate.cfg.xml”); 加载指定路径下指定名称的主配置文件
- config.buildSessionFactory(); 创建session的工厂对象
SessionFactory session的工厂（或者说代表了这个hibernate.cfg.xml配置文件）
- sf.openSession(); 创建一个sesison对象
- sf.getCurrentSession(); 创建session或取出session对象
Session session对象维护了一个连接(Connection), 代表了与数据库连接的会话。
- Hibernate最重要的对象：只用使用hibernate与数据库操作，都用到这个对象
- session.beginTransaction(); 开启一个事务；
  hibernate要求所有的与数据库的操作必须有事务的环境，否则报错！

更新：
- session.save(obj); 保存一个对象
- session.update(emp); 更新一个对象
- session.saveOrUpdate(emp); 保存或者更新的方法：
  - 没有设置主键，执行保存；
  - 有设置主键，执行更新操作;
  - 如果设置主键不存在报错！
主键查询：
- session.get(Employee.class, 1); 主键查询
- session.load(Employee.class, 1); 主键查询 (支持懒加载)
HQL查询
- HQL查询与SQL查询区别
  - SQL:(结构化查询语句) 查询的是表以及字段 ; 不区分大小写
  - HQL: hibernate query language 即hibernate提供的面向对象的查询语言
    - 查询的是对象以及对象的属性
    - 区分大小写

    /**
     * HQL查询
     * @throws Exception e
     */
    @Test
    public void testQuery() throws Exception{

        Session session = sessionFactory.openSession(); 
        Transaction transaction = session.beginTransaction();

        Query q = session.createQuery("from Employee");
//        Query q = session.createQuery("from Employee where empId=1 or empId=2");   带条件的查询
        List<Employee> list = q.list();

        System.out.println(list);
        transaction.commit();
        session.close();
    }

Criteria查询
- 完全面向对象的查询。

    /**
     * QBC查询  query by criteria 完全面向对象查询
     * @throws Exception e
     */
    @Test
    public void testQBC() throws Exception{

        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();

        Criteria criteria = session.createCriteria(Employee.class);
//        criteria.add(Restrictions.eq("empId",1)); 条件查询
        List<Employee> list = criteria.list();

        System.out.println(list);
        transaction.commit();
        session.close();
    }

本地SQL查询
复杂的查询，就要使用原生态的sql查询，也可以，就是本地sql查询的支持！
(缺点：不能跨数据库平台！)

    /**
     * sql查询
     * @throws Exception 异常
     */
    @Test
    public void testSql() throws Exception{
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();

//        SQLQuery sqlQuery = session.createSQLQuery("select * from employee");
        SQLQuery sqlQuery = session.createSQLQuery("select * from employee").addEntity(Employee.class);
        System.out.println(sqlQuery.list());

        transaction.commit();
    }

CRUD案例

//仅随手测试代码请忽略不够优化,也不要找我茬

public class HibernateUtils {

    private static SessionFactory sf;

    static {
        // 加载主配置文件, 并创建Session的工厂
        sf = new Configuration().configure().buildSessionFactory();
    }

    public static Session getSession(){
        return sf.openSession();
    }
}

public interface IEmployeeDao {

    void save(Employee employee);

    void update(Employee employee);

    void delete(Serializable id);

    Employee findById(Serializable id);

    List<Employee> getAll();

    List<Employee> getAll(String employeeName);

    List<Employee> getAll(int pageNo, int pageSize);
}

public class EmployeeDaoImpl implements IEmployeeDao {
    @Override
    public void save(Employee employee){
        Session session = null;
        Transaction tx = null;
        try{
            session = HibernateUtils.getSession();
            tx = session.beginTransaction();
            session.save(employee);
        }catch(Exception e){
            throw new RuntimeException(e);
        }finally{
            if(tx != null){
                tx.commit();
            }
            if(session != null){
                session.close();
            }
        }
    }

    @Override
    public void update(Employee employee){
        Session session = null;
        Transaction tx = null;
        try{
            session = HibernateUtils.getSession();
            tx = session.beginTransaction();
            session.update(employee);
        }catch(Exception e){
            throw new RuntimeException(e);
        }finally{
            if(tx != null){
                tx.commit();
            }
            if(session != null){
                session.close();
            }
        }
    }

    @Override
    public void delete(Serializable id){
        Session session = null;
        Transaction tx = null;
        try{
            session = HibernateUtils.getSession();
            tx = session.beginTransaction();
            Object obj = session.get(Employee.class, id);
            if(obj != null){
                session.delete(obj);
            }
        }catch(Exception e){
            throw new RuntimeException(e);
        }finally{
            if(tx != null){
                tx.commit();
            }
            if(session != null){
                session.close();
            }
        }
    }

    @Override
    public Employee findById(Serializable id){
        Session session = null;
        Transaction tx = null;
        try{
            session = HibernateUtils.getSession();
            tx = session.beginTransaction();
            return (Employee) session.get(Employee.class, id);
        }catch(Exception e){
            throw new RuntimeException(e);
        }finally{
            if(tx != null){
                tx.commit();
            }
            if(session != null){
                session.close();
            }
        }
    }

    @Override
    public List<Employee> getAll(){
        Session session = null;
        Transaction tx = null;
        try{
            session = HibernateUtils.getSession();
            tx = session.beginTransaction();
            Query q = session.createQuery("from Employee");
            return q.list();
        }catch(Exception e){
            throw new RuntimeException(e);
        }finally{
            if(tx != null){
                tx.commit();
            }
            if(session != null){
                session.close();
            }
        }
    }

    @Override
    public List<Employee> getAll(String employeeName){
        Session session = null;
        Transaction tx = null;
        try{
            session = HibernateUtils.getSession();
            tx = session.beginTransaction();
            Query q = session.createQuery("from Employee where empName = ?");
            // 注意: 参数索引从0开始
            q.setParameter(0, employeeName);
            return q.list();
        }catch(Exception e){
            throw new RuntimeException(e);
        }finally{
            if(tx != null){
                tx.commit();
            }
            if(session != null){
                session.close();
            }
        }
    }

    @Override
    public List<Employee> getAll(int pageNo, int pageSize){
        Session session = null;
        Transaction tx = null;
        try{
            session = HibernateUtils.getSession();
            tx = session.beginTransaction();
            Query query = session.createQuery("from Employee");
            // 设置分页参数
            query.setFirstResult(pageNo);
            query.setMaxResults(pageSize);
            List<Employee> list = query.list();
            return list;
        }catch(Exception e){
            throw new RuntimeException(e);
        }finally{
            if(tx != null){
                tx.commit();
            }
            if(session != null){
                session.close();
            }
        }
    }
}

java框架Hibernate入门

搭建环境及开发步骤

Hibernate的Api

CRUD案例

相关文章

网友评论

延伸阅读

深度阅读

栏目导航

热点阅读