java_DAO类基本设计

package cn.itcast.oa.base;

import java.util.List;

public interface BaseDao<T> {

    void save(T entity);

    void delete(Long id);

    void update(T entity);

    T getById(Long id);

    List<T> getByIds(Long[] ids);

    List<T> findAll();
}

package cn.itcast.oa.base;

import java.lang.reflect.ParameterizedType;
import java.util.Collections;
import java.util.List;

import javax.annotation.Resource;

import org.hibernate.Session;
import org.hibernate.SessionFactory;

@SuppressWarnings("unchecked")
public abstract class BaseDaoImpl<T> implements BaseDao<T> {

    @Resource
    private SessionFactory sessionFactory;
    protected Class<T> clazz; 

    public BaseDaoImpl() {
        // 通过反射得到T的真实类型
        ParameterizedType pt = (ParameterizedType) this.getClass().getGenericSuperclass();
        this.clazz = (Class) pt.getActualTypeArguments()[0];

        System.out.println("clazz = " + clazz.getName());
    }

    public void save(T entity) {
        getSession().save(entity);
    }

    public void update(T entity) {
        getSession().update(entity);
    }

    public void delete(Long id) {
        Object obj = getSession().get(clazz, id);
        getSession().delete(obj);
    }

    public T getById(Long id) {
        return (T) getSession().get(clazz, id);
    }

    public List<T> getByIds(Long[] ids) {
        if (ids == null || ids.length == 0) {
            return Collections.EMPTY_LIST;
        }

        return getSession().createQuery(//
                "FROM " + clazz.getSimpleName() + " WHERE id IN(:ids)")//
                .setParameterList("ids", ids)//
                .list();
    }

    public List<T> findAll() {
        return getSession().createQuery(//
                "FROM " + clazz.getSimpleName())//
                .list();
    }

    /**
     * 获取当前可用的Session
     *
     * @return
     */
    protected Session getSession() {
        return sessionFactory.getCurrentSession();
    }

}

package cn.itcast.oa.dao;

import cn.itcast.oa.base.BaseDao;
import cn.itcast.oa.domain.Role;

public interface RoleDao extends BaseDao<Role>{

}

package cn.itcast.oa.dao;

import cn.itcast.oa.base.BaseDao;
import cn.itcast.oa.domain.User;

public interface UserDao extends BaseDao<User> {

}

package cn.itcast.oa.dao.impl;

import org.springframework.stereotype.Repository;

import cn.itcast.oa.base.BaseDaoImpl;
import cn.itcast.oa.dao.RoleDao;
import cn.itcast.oa.domain.Role;

@Repository
public class RoleDaoImpl extends BaseDaoImpl<Role> implements RoleDao {

    // public RoleDaoImpl(){
    // clazz = Role.class;
    // }
}

package cn.itcast.oa.dao.impl;

import org.springframework.stereotype.Repository;

import cn.itcast.oa.base.BaseDaoImpl;
import cn.itcast.oa.dao.UserDao;
import cn.itcast.oa.domain.User;

@Repository
public class UserDaoImpl extends BaseDaoImpl<User> implements UserDao {

    // public UserDaoImpl(){
    // clazz = User.class;
    // }
}