MyBatis通用dao和通用service

2018/05/17 11:29
阅读数 1.1K

更新于2015/01/29,增加了第三种方法

##更新于2015/02/09,第三种方法方法改进,service实现上不需要加泛型

概述:

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

第一种:需要三个泛型,当前实体对象,主键,映射对象,

好处:具体Service实现类简单,如果自己没有特殊的方法,继承BaseServiceImpl之后不需要写任何东西

不好之处:

  1. 每个通用方法都需要传递映射参数:比如findById,如果是UserService调用,则需要这样写:userService.findById(1,UserMapper.class),这样在BaseMapperImpl中才可以通过class.getName得到映射的名称

  2. 而且在BaseMapperImpl中写得比较死。修改起来比较复杂

第二种:

第一:不需要在方法上写各种泛型参数,同时也不需要在各种方法中传递映射参数

第二:通用dao也不需要写实现:mybatis-spring所倡导的的一致

不好之处:

需要在每个Service实现类中写上:

@Autowired
    public void setBaseMapper(UserMapper userMapper){

        super.setBaseMapper(userMapper);
    }

而且关键的是@Autowired不能少。这个在开发过程中不好进行限制

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;
  }
}

第三种:更新于2015/01/31,增加了第三种方法

这一种算是第二种的改进。避免了在ServiceImpl中写@Autowired

去掉,privste BaseMapper<T,ID> baseMapper。

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>{
  @Override
  public abstract BaseMapper<T, ID> getMapper() ;
  @Override
  public int deleteByPrimaryKey(ID id) {
    return getMapper().deleteByPrimaryKey(id);
  }
  @Override
  public int insert(T record) {
    return getMapper().insert(record);
  }
  @Override
  public int insertSelective(T record) {
    return getMapper().insertSelective(record);
  }
  @Override
  public T selectByPrimaryKey(ID id) {
    return getMapper().selectByPrimaryKey(id);
  }
  @Override
  public int updateByPrimaryKeySelective(T record) {
    return getMapper().updateByPrimaryKeySelective(record);
  }
  @Override
  public int updateByPrimaryKeyWithBLOBs(T record) {
    return getMapper().updateByPrimaryKeyWithBLOBs(record);
  }
  @Override
  public int updateByPrimaryKey(T record) {
    return getMapper().updateByPrimaryKey(record);
  }
}

具体的Service实现。在这个里面,通过抽象的Service,来强制具体Service实现getMapper方法,而不需要在该方法上加@Autowired。

package cn.liuyiyou.yishop.service.impl;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import cn.liuyiyou.yishop.domain.Ad;
import cn.liuyiyou.yishop.mapper.AdMapper;
import cn.liuyiyou.yishop.mapper.BaseMapper;
import cn.liuyiyou.yishop.service.AdService;
import cn.liuyiyou.yishop.service.BaseService;
@Service
public class AdServiceImpl extends AbstractService<Ad,Long> implements AdService {
  @Autowired
  public AdMapper adMapper;
  @Override
  public BaseMapper<Ad, Long> getMapper() {
    return adMapper;
  }
}

最近更新于2015/02/09,第三种方法方法改进,service实现上不需要加泛型

之所以记录下来的原因是因为,在service接口上没有使用泛型

package cn.liuyiyou.springmvc.mapper;
import java.io.Serializable;
/**
 * User: liuyiyou
 * Date: 14-12-27
 * Time: 下午11:39
 */
public interface BaseMapper<T,ID extends Serializable> {
  //只需要这个就可以了,并不需要具体的实现,只需要在Service中设置BaseMapper
  T findById(ID id);
  Integer insert(T t);
}
package cn.liuyiyou.springmvc.service;
import java.io.Serializable;
/**
 * User: liuyiyou
 * Date: 14-12-27
 * Time: 下午11:53
 */
public interface BaseService <T,ID extends Serializable>{
  T findById(ID id);
  int insert(T t);
}
package cn.liuyiyou.springmvc.service;
import cn.liuyiyou.springmvc.mapper.BaseMapper;
import java.io.Serializable;
/**
 * User: liuyiyou
 * Date: 14-12-27
 * Time: 下午11:54
 */
public abstract class BaseServiceImpl<T,ID extends Serializable> implements BaseService<T,ID> {
   public abstract  BaseMapper getMapper();
  @Override
  public T findById(ID id) {
    return (T) getMapper().findById(id);
  }
  @Override
  public int insert(T t) {
    return getMapper().insert(t);
  }
}
package cn.liuyiyou.springmvc.service;
import cn.liuyiyou.springmvc.domain.User;
public interface UserService extends BaseService {
  boolean addUser(User user);
}
package cn.liuyiyou.springmvc.service;
import cn.liuyiyou.springmvc.mapper.BaseMapper;
import cn.liuyiyou.springmvc.mapper.UserMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import cn.liuyiyou.springmvc.domain.User;
@Service
@Transactional(value="transactionManager")
public class UserServiceImpl extends BaseServiceImpl  implements UserService{
  @Autowired
  private UserMapper userMapper;
  @Override
  public BaseMapper getMapper(){
    return userMapper;
  }
  public boolean addUser(User user) {
    int reuslt = userMapper.insert(user);
    if (reuslt>0)
      return true;
    return	false;
  }
}

 

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