使用mybatis完成通用dao和通用service

使用通用dao和通用service可以减少代码的开发。可以将常用的增删改查放到通用dao中。对不同的or框架，基本上都有自己的实现如SpringJPA的Repository就提供了常用的增删改查方法。而MyBatis借助代码生成工具也可以生成常用方法的映射

这里只针对Mybatis。如果使用代码生成工具，会有一个问题：每个Mapper里面都有一些方法（增晒改查）。维护起来的话还好。只是在写service的时候会有一个问题。比如UserMapper里面有 insert(User user) ， find(Integer id) , delete(Integer id) 等方法，则在service中也要有这些方法的实现。假设每个Mapper有5个方法。则service也需要有5个方法的实现。如果有10个实体类。mapper可以省略（由生成工具生成），但是service有50个方法。到后期肯定不好进行维护

使用通用Mapper和Service

该通用Mapper使用了Spring-mybatis。所以没有实现类，而是直接调用xml文件中的同名方法。之所以将通用Mapper抽出来主要是为了方便些通用的service

具体代码

1. 通用接口，该接口方法的名称与使用代码生成工具的名称完全相同

package cn.liuyiyou.yishop.mapper;
import java.io.Serializable;
public interface BaseMapper<T,ID extends Serializable> {
	int deleteByPrimaryKey(ID id);
	int insert(T record);
	int insertSelective(T record);
	T selectByPrimaryKey(ID id);
	int updateByPrimaryKeySelective(T record);
	int updateByPrimaryKeyWithBLOBs(T record);
	int updateByPrimaryKey(T record);
}

1. 通用service接口。为了方便，名字和通用Mapper同名，其实更倾向于命名add。edit，find这类的命名，显得更加面向对象

package cn.liuyiyou.yishop.service;
import java.io.Serializable;
public interface BaseService<T,ID extends Serializable> {
	void setBaseMapper();
	int deleteByPrimaryKey(ID id);
	int insert(T record);
	int insertSelective(T record);
	T selectByPrimaryKey(ID id);
	int updateByPrimaryKeySelective(T record);
	int updateByPrimaryKeyWithBLOBs(T record);
	int updateByPrimaryKey(T record);
}

1. 通用service实现。也很简单。就是调用通用mapper里面的方法即可

package cn.liuyiyou.yishop.service.impl;
import java.io.Serializable;
import cn.liuyiyou.yishop.mapper.BaseMapper;
import cn.liuyiyou.yishop.service.BaseService;
public abstract  class AbstractService<T, ID extends Serializable> implements BaseService<T, ID> {
	private BaseMapper<T, ID> baseMapper;
	public void setBaseMapper(BaseMapper<T, ID> baseMapper) {
		this.baseMapper = baseMapper;
	}
	@Override
	public int deleteByPrimaryKey(ID id) {
		return baseMapper.deleteByPrimaryKey(id);
	}
	@Override
	public int insertSelective(T record) {
		return baseMapper.insertSelective(record);
	}
	@Override
	public T selectByPrimaryKey(ID id) {
		return baseMapper.selectByPrimaryKey(id);
	}
	@Override
	public int updateByPrimaryKeySelective(T record) {
		return baseMapper.updateByPrimaryKey(record);
	}
	@Override
	public int updateByPrimaryKeyWithBLOBs(T record) {
		return baseMapper.updateByPrimaryKeyWithBLOBs(record);
	}
	@Override
	public int updateByPrimaryKey(T record) {
		return baseMapper.updateByPrimaryKey(record);
	}
	@Override
	public int insert(T record) {
		return baseMapper.insert(record);
	}
}

1. 具体的Mapper写法:

package cn.liuyiyou.yishop.mapper;
import java.util.List;
import org.springframework.stereotype.Repository;
import cn.liuyiyou.yishop.domain.ProductCategory;
@Repository
public interface ProductCategoryMapper extends BaseMapper<ProductCategory, Long>{
	/**
	 * 通过父id得到类目列表
	 * @param praentId
	 * @return
	 */
	List<ProductCategory> selectByParent(Long parent);
}

1. 具体的Servicd

package cn.liuyiyou.yishop.service.impl;
import java.util.HashMap;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import cn.liuyiyou.yishop.domain.Ad;
import cn.liuyiyou.yishop.domain.Product;
import cn.liuyiyou.yishop.mapper.AdMapper;
import cn.liuyiyou.yishop.mapper.ProductMapper;
import cn.liuyiyou.yishop.service.ProductService;
@Service
public class ProductServiceImpl extends AbstractService<Product,Long> implements ProductService {
	@Autowired
	private ProductMapper productMapper;
	@Autowired
	private AdMapper adMapper;
	//这句必须要加上。不然会报空指针异常，因为在实际掉用的时候不是BaseMapper调用，而是这个productMapper
	@Autowired
	public void setBaseMapper(){
		super.setBaseMapper(productMapper);
	}
	@Override
	public Map<String,Object> testTwo() {
		Product product = productMapper.selectByPrimaryKey(1l);
		Ad ad = adMapper.selectByPrimaryKey(1l);
		Map<String,Object> map = new HashMap<String,Object>();
		map.put("product", product);
		map.put("ad", ad);
		return map;
	}
}

资料

http://liuyiyou.cn/2014/12/28/base-dao-service/ –这个好像有提到好坏