这两天又捡起来老司机的web端代码，需要增加一些新的功能，比如说充值卡（PrepaidCard）模块。在写Dao层的时候发现好麻烦呀，每个实体类都要写一个对应的Dao（还包括接口跟实现），而大部分Dao方法都是基本的增删查改操作（CRUD）。比如getById，save，update，count，query，delete。而这些基本操作的代码其实都是相差无几的，既然这样那我们是不是可以写一个BaseDao来实现基本操作，然后让其他Dao来继承他。
以我现在要写的PrepaidCard实体类为例：
/**
* 省略各种import
**/
@Entity
@Table(name = "fp_prepaid_card")
public class PrepaidCard implements Serializable {
private static final long serialVersionUID = 1L;
@Column(name = "id")
@Id
@GeneratedValue
private long id;
@Column(name = "token", unique = true, length = 36, nullable = false)
private String token;
@Column(name = "days")
private long days;
@Column(name = "created_time", columnDefinition = "DATETIME", nullable = false)
private Date createdTime;
@Column(name = "used_time", columnDefinition = "DATETIME", nullable = false)
private Date usedTime;
@JoinColumn(name = "consumer_id", referencedColumnName = "id")
@ManyToOne(targetEntity = User.class, fetch = FetchType.EAGER, cascade = {})
private User user;
/**
* 省略各种方法
**/
}
1、没有实现BaseDao时候的PrepaidCardDao
package com.funway.fproxy.dao;
import java.util.List;
import org.hibernate.criterion.DetachedCriteria;
import com.funway.fproxy.domain.PrepaidCard;
public interface PrepaidCardDao {
/**
* 根据序列号获取充值卡
* @param token
* @return
*/
PrepaidCard getPrepadiCardByToken(String token);
/**
* 保存充值卡信息
* 对应sql语句是insert，会立即执行
* @param prepaidCard
*/
void save(PrepaidCard prepaidCard);
/**
* 更新充值卡信息
* 对应sql语句是update，不会立即执行，等待flush
* @param prepaidCard
*/
void update(PrepaidCard prepaidCard);
/**
* 按条件统计
* @param deCriteria
* @return
*/
long count(DetachedCriteria deCriteria);
/**
* 按条件查询，不支持分页
* @param deCriteria 查询条件
* @return
*/
List<PrepaidCard> query(DetachedCriteria deCriteria);
/**
* 按条件查询，支持分页
* @param deCriteria 查询条件
* @param page 第几页（从1开始；负数或0时page等效于1）
* @param pageSize 每页行数（负数或0时pageSize无效，取所有行）
* @return
*/
List<PrepaidCard> query(DetachedCriteria deCriteria, int page, int pageSize);
}
package com.funway.fproxy.dao.impl;
import java.util.List;
import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.criterion.DetachedCriteria;
import org.hibernate.criterion.Projections;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;
import com.funway.fproxy.dao.PrepaidCardDao;
import com.funway.fproxy.domain.PrepaidCard;
@Repository
public class PrepadiCardDaoImpl implements PrepaidCardDao {
@Autowired
private SessionFactory sessionFactory;
@Override
public PrepaidCard getPrepadiCardByToken(String token) {
String hqlQueryString = "from PrepaidCard as pc where pc.token = :token";
Session session = sessionFactory.openSession();
try {
Query query = session.createQuery(hqlQueryString).setString("token", token);
PrepaidCard prepaidCard = (PrepaidCard) query.uniqueResult();
return prepaidCard;
} finally {
session.close();
}
}
@Override
public void save(PrepaidCard prepaidCard) {
Session session = sessionFactory.getCurrentSession();
session.save(prepaidCard);
}
@Override
public void update(PrepaidCard prepaidCard) {
Session session = sessionFactory.getCurrentSession();
session.update(prepaidCard);
}
@Override
public long count(DetachedCriteria deCriteria) {
Session session = sessionFactory.openSession();
try {
deCriteria.setProjection(Projections.rowCount());
long count = (long) deCriteria.getExecutableCriteria(session).uniqueResult();
return count;
} finally {
session.close();
}
}
@Override
public List<PrepaidCard> query(DetachedCriteria deCriteria) {
return query(deCriteria, 1, 0);
}
@SuppressWarnings("unchecked")
@Override
public List<PrepaidCard> query(DetachedCriteria deCriteria, int page, int pageSize) {
Session session = sessionFactory.openSession();
try {
Criteria criteria = deCriteria.getExecutableCriteria(session);
criteria.setFirstResult((page - 1) * pageSize);
criteria.setMaxResults(pageSize);
List<PrepaidCard> prepaidCards = criteria.list();
return prepaidCards;
} finally {
session.close();
}
}
}
2、实现BaseDao
我们在BaseDao中只定义了常用的CRUD操作，子类可以重写，或者新增自己特定的方法。
package com.funway.fproxy.dao;
import java.io.Serializable;
import java.util.List;
import org.hibernate.criterion.DetachedCriteria;
public interface BaseDao<T> {
/**
* 保存实体
* 对应sql为insert，立即执行
* @param entity
*/
public void save(T entity);
/**
* 更新实体
* 对应sql为update，不立即执行，等待flush
* @param entity
*/
public void update(T entity);
/**
* 删除实体
* @param entity
*/
public void delete(T entity);
/**
* 根据主键查找实体
* @param id
* @return
*/
public T getById(Serializable id);
/**
* 按条件统计
* @param deCriteria
* @return
*/
public long count(DetachedCriteria deCriteria);
/**
* 按条件查询，不支持分页
* @param deCriteria 查询条件
* @return
*/
public List<T> query(DetachedCriteria deCriteria);
/**
* 按条件查询，支持分页
*
* @param deCriteria
* 查询条件
* @param page
* 第几页（从1开始；负数或0时page等效于1）
* @param pageSize
* 每页行数（负数或0时pageSize无效，取所有行）
* @return
*/
public List<T> query(DetachedCriteria deCriteria, int page, int pageSize);
}
package com.funway.fproxy.dao.impl;
import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.util.List;
import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.criterion.DetachedCriteria;
import org.hibernate.criterion.Projections;
import org.springframework.beans.factory.annotation.Autowired;
import com.funway.fproxy.dao.BaseDao;
@SuppressWarnings("unchecked")
public class BaseDaoImpl<T> implements BaseDao<T> {
@Autowired
protected SessionFactory sessionFactory;
/**
* 泛型T的实际类型
*/
private Class<T> entityClass;
public BaseDaoImpl() {
// 获得泛型T的实际类型
ParameterizedType type = (ParameterizedType) getClass().getGenericSuperclass();
this.entityClass = (Class<T>) type.getActualTypeArguments()[0];
// System.out.println("实体类型: " + this.entityClass.getName());
}
@Override
public void save(T entity) {
Session session = sessionFactory.getCurrentSession();
session.save(entity);
}
@Override
public void update(T entity) {
Session session = sessionFactory.getCurrentSession();
session.update(entity);
}
@Override
public void delete(T entity) {
Session session = sessionFactory.getCurrentSession();
session.delete(entity);
}
@Override
public T getById(Serializable id) {
Session session = sessionFactory.openSession();
try {
T result = (T) session.get(entityClass, id);
return result;
} finally {
session.close();
}
}
@Override
public long count(DetachedCriteria deCriteria) {
Session session = sessionFactory.openSession();
try {
deCriteria.setProjection(Projections.rowCount());
long count = (long) deCriteria.getExecutableCriteria(session).uniqueResult();
return count;
} finally {
session.close();
}
}
@Override
public List<T> query(DetachedCriteria deCriteria) {
return query(deCriteria, 1, 0);
}
@Override
public List<T> query(DetachedCriteria deCriteria, int page, int pageSize) {
Session session = sessionFactory.openSession();
try {
Criteria criteria = deCriteria.getExecutableCriteria(session);
criteria.setFirstResult((page - 1) * pageSize);
criteria.setMaxResults(pageSize);
List<T> entities = criteria.list();
return entities;
} finally {
session.close();
}
}
}
3、继承了BaseDao的PrepaidCardDao
修改我们之前写的PrepaidCardDao/PrepaidCardDaoImpl代码，通过继承BaseDao来获得通用的CRUD方法。
package com.funway.fproxy.dao;
import com.funway.fproxy.domain.PrepaidCard;
public interface PrepaidCardDao extends BaseDao<PrepaidCard> {
/**
* 根据序列号获取充值卡
* @param token
* @return
*/
PrepaidCard getPrepadiCardByToken(String token);
}
package com.funway.fproxy.dao.impl;
import org.hibernate.Query;
import org.hibernate.Session;
import org.springframework.stereotype.Repository;
import com.funway.fproxy.dao.PrepaidCardDao;
import com.funway.fproxy.domain.PrepaidCard;
@Repository
public class PrepaidCardDaoImpl extends BaseDaoImpl<PrepaidCard> implements PrepaidCardDao {
@Override
public PrepaidCard getPrepadiCardByToken(String token) {
String hqlQueryString = "from PrepaidCard as pc where pc.token = :token";
Session session = sessionFactory.openSession();
try {
Query query = session.createQuery(hqlQueryString).setString("token", token);
PrepaidCard prepaidCard = (PrepaidCard) query.uniqueResult();
return prepaidCard;
} finally {
session.close();
}
}
}
参考：