案例50-crm练习dao层的抽取BaseDao

1 抽取BaseDao

2 BaseDao设计思路

3 BaseDao接口书写

package www.test.dao;

import java.io.Serializable;
import java.util.List;

import org.hibernate.criterion.DetachedCriteria;

public interface BaseDao<T> {

    //增
    void save(T t);

    //删
    void delete(T t);

    //删  Serializable包括了8大包装类型
    void delete(Serializable id);

    //改
    void update(T t);

    //查 根据id查询
    T getById(Serializable id);

    //查  符合条件的总记录数
    Integer getTotalCount(DetachedCriteria dc);

    //查 查询分页列表数据
    List<T> getPageList(DetachedCriteria dc,Integer start,Integer pageSize);

}

4 BaseDao的实现类

package www.test.dao.impl;

import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.util.List;

import org.hibernate.criterion.DetachedCriteria;
import org.hibernate.criterion.Projections;
import org.springframework.orm.hibernate5.support.HibernateDaoSupport;

import www.test.dao.BaseDao;

public class BaseDaoImpl<T> extends HibernateDaoSupport implements BaseDao<T> {

    private Class clazz; // 用于接收运行期泛型类型

    public BaseDaoImpl() {
        // 获得当前类型的带有泛型类型的父类
        // this.getClass().getGenericSuperclass();运行在BaseDaoImpl的儿子(谁继承了它)
        // 所以它的父类就是BaseDaoImpl
        ParameterizedType ptClass = (ParameterizedType) this.getClass().getGenericSuperclass();

        // 获得运行期的泛型类型
        clazz = (Class) ptClass.getActualTypeArguments()[0];
    }

    @Override
    public void save(T t) {
        super.getHibernateTemplate().save(t);
    }

    @Override
    public void delete(T t) {
        super.getHibernateTemplate().delete(t);
    }

    @Override
    public void delete(Serializable id) {
        // 先获取，然后在删除
        T t = this.getById(id);
        super.getHibernateTemplate().delete(t);
    }

    @Override
    public void update(T t) {
        super.getHibernateTemplate().update(t);
    }

    @Override
    public T getById(Serializable id) {
        return (T) super.getHibernateTemplate().get(clazz, id);

    }

    @Override
    public Integer getTotalCount(DetachedCriteria dc) {
        // 设置查询聚合函数，总记录数
        dc.setProjection(Projections.rowCount());

        List<Long> list = (List<Long>) super.getHibernateTemplate().findByCriteria(dc);

        // 清空之前设置的聚合函数
        dc.setProjection(null);

        if (list != null && list.size() > 0) {
            Long count = list.get(0);
            return count.intValue();
        } else {
            return null;
        }
    }

    @Override
    public List<T> getPageList(DetachedCriteria dc, Integer start, Integer pageSize) {

        List<T> list = (List<T>) super.getHibernateTemplate().findByCriteria(dc, start, pageSize);

        return list;
    }

}

5 业务Dao中的应用

package www.test.dao;

import www.test.domain.Customer;

public interface CustomerDao extends BaseDao<Customer>{

}

package www.test.dao.impl;

import www.test.dao.CustomerDao;
import www.test.domain.Customer;

public class CustomerDaoImpl extends BaseDaoImpl<Customer> implements CustomerDao{

}