使用通用dao和通用service可以減少代碼的開發。可以將常用的增刪改查放到通用dao中。對不同的or框架，基本上都有自己的實現如SpringJPA的Repository就提供了常用的增刪改查方法。而MyBatis借助代碼生成工具也可以生成常用方法的映射

這裏只針對Mybatis。如果使用代碼生成工具，會有一個問題：每個Mapper裏面都有一些方法（增曬改查）。維護起來的話還好。只是在寫service的時候會有一個問題。比如UserMapper裏面有 insert(User user) ， find(Integer id) , delete(Integer id) 等方法，則在service中也要有這些方法的實現。假設每個Mapper有5個方法。則service也需要有5個方法的實現。如果有10個實體類。mapper可以省略（由生成工具生成），但是service有50個方法。到後期肯定不好進行維護

使用通用Mapper和Service

該通用Mapper使用了Spring-mybatis。所以沒有實現類，而是直接調用xml文件中的同名方法。之所以將通用Mapper抽出來主要是為了方便些通用的service

具體代碼

1. 通用接口，該接口方法的名稱與使用代碼生成工具的名稱完全相同

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。為了方便，名字和通用Mapper同名，其實更傾向於命名add。edit，find這類的命名，顯得更加面向對象

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實現。也很簡單。就是調用通用mapper裏面的方法即可

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. 具體的Mapper寫法:

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>{
	/**
	 * 通過父id得到類目列表
	 * @param praentId
	 * @return
	 */
	List<ProductCategory> selectByParent(Long parent);
}

1. 具體的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;
	//這句必須要加上。不然會報空指針異常，因為在實際掉用的時候不是BaseMapper調用，而是這個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;
	}
}

資料

http://liuyiyou.cn/2014/12/28/base-dao-service/ –這個好像有提到好壞

使用mybatis完成通用dao和通用service