package com.example.library.Mapper;
import com.example.library.entity.bookBorrowing;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
public interface borrowMapper extends BaseMapper<bookBorrowing>{
 
}

其中BaseMapper中接口就有該函數(shù)：

 
  // IntelliJ API Decompiler stub source generated from a class file
  // Implementation of methods is not available
 
package com.baomidou.mybatisplus.core.mapper;
 
public interface BaseMapper <T> extends com.baomidou.mybatisplus.core.mapper.Mapper<T> {
    int insert(T entity);
 
    int deleteById(java.io.Serializable id);
 
    int deleteByMap(@org.apache.ibatis.annotations.Param("cm") java.util.Map<java.lang.String,java.lang.Object> columnMap);
 
    int delete(@org.apache.ibatis.annotations.Param("ew") com.baomidou.mybatisplus.core.conditions.Wrapper<T> queryWrapper);
 
    int deleteBatchIds(@org.apache.ibatis.annotations.Param("coll") java.util.Collection<? extends java.io.Serializable> idList);
 
    int updateById(@org.apache.ibatis.annotations.Param("et") T entity);
 
    int update(@org.apache.ibatis.annotations.Param("et") T entity, @org.apache.ibatis.annotations.Param("ew") com.baomidou.mybatisplus.core.conditions.Wrapper<T> updateWrapper);
 
    T selectById(java.io.Serializable id);
 
    java.util.List<T> selectBatchIds(@org.apache.ibatis.annotations.Param("coll") java.util.Collection<? extends java.io.Serializable> idList);
 
    java.util.List<T> selectByMap(@org.apache.ibatis.annotations.Param("cm") java.util.Map<java.lang.String,java.lang.Object> columnMap);
 
    T selectOne(@org.apache.ibatis.annotations.Param("ew") com.baomidou.mybatisplus.core.conditions.Wrapper<T> queryWrapper);
 
    java.lang.Integer selectCount(@org.apache.ibatis.annotations.Param("ew") com.baomidou.mybatisplus.core.conditions.Wrapper<T> queryWrapper);
 
    java.util.List<T> selectList(@org.apache.ibatis.annotations.Param("ew") com.baomidou.mybatisplus.core.conditions.Wrapper<T> queryWrapper);
 
    java.util.List<java.util.Map<java.lang.String,java.lang.Object>> selectMaps(@org.apache.ibatis.annotations.Param("ew") com.baomidou.mybatisplus.core.conditions.Wrapper<T> queryWrapper);
 
    java.util.List<java.lang.Object> selectObjs(@org.apache.ibatis.annotations.Param("ew") com.baomidou.mybatisplus.core.conditions.Wrapper<T> queryWrapper);
 
    <E extends com.baomidou.mybatisplus.core.metadata.IPage<T>> E selectPage(E page, @org.apache.ibatis.annotations.Param("ew") com.baomidou.mybatisplus.core.conditions.Wrapper<T> queryWrapper);
 
    <E extends com.baomidou.mybatisplus.core.metadata.IPage<java.util.Map<java.lang.String,java.lang.Object>>> E selectMapsPage(E page, @org.apache.ibatis.annotations.Param("ew") com.baomidou.mybatisplus.core.conditions.Wrapper<T> queryWrapper);
}

其中的selectByMap調(diào)用的就是其中的函數(shù)。

接下來就是調(diào)用的方法：

package com.example.library;
 
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.conditions.update.UpdateWrapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import com.example.library.Mapper.*;
import com.example.library.entity.*;
import org.mybatis.spring.annotation.MapperScan;
 
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
@MapperScan("com/example/library/Mapper")
@SpringBootTest
 
class LibraryApplicationTests {
 
    @Autowired
    private borrowMapper borrowMapper;
 
    @Test
    public void mapSelect(){
        Map<String,Object> map = new HashMap<String, Object>();
        map.put("student_code","123456");
        List<bookBorrowing> stu = borrowMapper.selectByMap(map);
        for(bookBorrowing s:stu){
            System.out.println(s);
        }
    }
}

@Test注解是表示這是一個(gè)測試類，可以單獨(dú)拎出來測試。

這條語句是，將查到的student_code為123456的那一行信息拿出來并打印在控制臺上。

這是數(shù)據(jù)庫中的相關(guān)信息：