基于Mybatis-Plus的CRUD

使用mybatis-plus自动生成了5个模块(xml/bean/mapper/service/controller)的代码,这里练习一下mybatis-plus框架下的CRUD.

还是原先的那个springboot项目.

mybatis-plus也是mybatis的增强版,它并未改变mybatis原有功能,只是在传统mybatis原有基础上又新增了一些功能,用以提高开发效率.

比如,在mybatis-plus框架下,项目mapper层接口可通过继承BaseMapper,获取基本的CRUD功能,而无需编写mapper.xml语句.

AutoGenerator自动生成的mapper.xml如下所示:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://www.mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<mapper namespace="cn.example.demo.mapper.SoldierMapper">

    <!-- 通用查询映射结果 -->
    <resultMap id="BaseResultMap" type="cn.example.demo.bean.Soldier">
        <id column="soldier_id" property="soldierId" />
        <result column="soldier_name" property="soldierName" />
        <result column="join_army_time" property="joinArmyTime" />
    </resultMap>

    <!-- 通用查询结果列 -->
    <sql id="Base_Column_List">
        soldier_id, soldier_name, join_army_time
    </sql>

</mapper>

下面的Mapper接口也是自动生成的,里面什么都不用写:

/**
 * <p>
 * Mapper 接口
 * </p>
 *
 * @author gene
 * @since 2019-09-11
 */
public interface SoldierMapper extends BaseMapper<Soldier> {
    
}

项目集成mybatis-plus之后,在大多数CRUD情景下,可以跳过mapper层,直接到业务层接口写接口方法,然后在业务实现类里调用BaseMapper接口内的方法即可.

业务接口(要自己动手写了):

package cn.example.demo.service;

import java.util.List;

import com.baomidou.mybatisplus.core.conditions.Wrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.IService;

import cn.example.demo.bean.Soldier;

/**
 * <p>
 * 服务类
 * </p>
 *
 * @author gene
 * @since 2019-09-11
 */
public interface SoldierService extends IService<Soldier> {
    /**
     * 增加
     * 
     * @param soldier
     * @return
     */
    int insert(Soldier soldier);

    /**
     * 查询全部
     * 
     * @return
     */
    List<Soldier> selectAll(Wrapper<Soldier> queryWrapper);

    /**
     * 据ID而查
     * 
     * @param soldier
     * @return
     */
    Soldier selectById(Integer soldierId);

    /**
     * 更改1行
     * 
     * @param soldier
     * @return
     */
    int updateOne(Soldier soldier);

    /**
     * 删除一行
     * 
     * @param soldier
     * @return
     */
    int deleteOne(Soldier soldier);
}

实现类:

package cn.example.demo.service.impl;

import com.baomidou.mybatisplus.core.conditions.Wrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;

import cn.example.demo.bean.Soldier;
import cn.example.demo.mapper.SoldierMapper;
import cn.example.demo.service.SoldierService;

import java.util.List;

import org.springframework.stereotype.Service;

/**
 * <p>
 * 服务实现类
 * </p>
 *
 * @author gene
 * @since 2019-09-11
 */
@Service
public class SoldierServiceImpl extends ServiceImpl<SoldierMapper, Soldier> implements SoldierService {

    @Override
    public int insert(Soldier soldier) {
        return baseMapper.insert(soldier);
    }

    @Override
    public List<Soldier> selectAll(Wrapper<Soldier> queryWrapper) {
        return baseMapper.selectList(queryWrapper);
    }

    @Override
    public Soldier selectById(Integer soldierId) {
        return baseMapper.selectById(soldierId);
    }

    @Override
    public int updateOne(Soldier soldier) {
        return baseMapper.updateById(soldier);
    }

    @Override
    public int deleteOne(Soldier soldier) {
        return baseMapper.deleteById(soldier);
    }

}

测试方法,贴一个"增":

    @Autowired
    private SoldierService ss;


    @Test
    public void insertTest() {
        LocalDateTime now = LocalDateTime.now();

        Soldier soldier = new Soldier("yaobuqi", now);

        int affect = ss.insert(soldier);

        System.err.println("affect- " + affect);
    }

收工.

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最后是测试期间遇到的异常:

• java.lang.NoSuchMethodError: org.apache.ibatis.session.Configuration.getDefaultScriptingLanguageInstance() Lorg/apache/ibatis/scripting/LanguageDriver

  • 升级mybatis-spring-boot-starter版本至2.1.0
  • 升级mybatis-generator-core版本至1.3.7

__

• dao.InvalidDataAccessApiUsageException: Error attempting to get column 'join_army_time' from result set. Cause: java.sql.SQLFeatureNotSupportedException; null; nested exception is java.sql.SQLFeatureNotSupportedException

简而言之:使用mybatis-plus逆向工程会将数据库中的date类型转换为LocalDateTime，访问接口的时候报错:java.sql.SQLFeatureNotSupportedException.

这是因为druid跟mybatis3.5.1兼容性问题,mybatis-plus-generator 3.1.2引用了mybatis3.5.1版本,而druid-boot-1.1.18尚未与之兼容,应将mybatis-plus版本降至3.1.0或以下即可.

如果上面的法子无效,那就更换druid数据源为hikaricp数据源:

    <dependency>
        <groupId>com.zaxxer</groupId>
        <artifactId>HikariCP</artifactId>
        <version>3.3.1</version>
    </dependency>

还有一种方法是,把实体类成员的LocalDateTime类型换为Date类型.

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