环境准备：
创建模块 ，引入相关依赖 和 配置文件
创建数据库表：t_student
向数据库表中填充数据
创建pojo类 ：student
public class Student {private Long id;private String name;private Integer age;private Double height;private Date birth;private Character sex; }
1. 单个简单类型参数
简单类型包括：
- byte short int long float double char
- Byte Short Integer Long Float Double Character
- String
- java.util.Date
- java.sql.Date
通过下面所写代码测试得知，简单类型对于mybatis来说都是可以自动类型识别的：
- 也就是说对于mybatis来说，它是可以自动推断出ps.setXxxx()方法的。ps.setString()还是ps.setInt()。它可以自动推断。
其实SQL映射文件中的配置比较完整的写法是
<select id="selectByName" resultType="student" parameterType="java.lang.String">select * from t_student where name = #{name, javaType=String, jdbcType=VARCHAR}
</select>
其中sql语句中的javaType，jdbcType，以及select标签中的parameterType属性，都是用来帮助mybatis进行类型确定的。不过这些配置多数是可以省略的。因为mybatis它有强大的自动类型推断机制。
- javaType：可以省略
- jdbcType：可以省略
- parameterType：可以省略
如果参数只有一个的话，#{} 里面的内容就随便写了。对于 ${} 来说，注意加单引号。
StudentMapper接口 ， 需求：根据name查、根据id查、根据birth查、根据sex查
package com.north.mybatis.mapper;import com.north.mybatis.pojo.Student;import java.util.Date;
import java.util.List;/*** @Author North* @Date 2024/4/7*/
public interface StudentMapper {Student selectById(Long id);List<Student> selectByName(String name);List<Student> selectByBirth(Date birth);List<Student> selectBySex(char sex);
}
StudentMapper.xml 映射文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.north.mybatis.mapper.StudentMapper"><select id="selectById" resultType="Student">select * from t_student where id = #{id}</select><select id="selectByName" resultType="Student">select * from t_student where name = #{name}</select><select id="selectByBirth" resultType="Student">select * from t_student where birth = #{birth}</select><select id="selectBySex" resultType="Student">select * from t_student where sex = #{sex}</select>
</mapper>
测试类：
package com.north.mybatis.test;import com.north.mybatis.mapper.StudentMapper;
import com.north.mybatis.pojo.Student;
import com.north.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;/*** @Author North* @Date 2024/4/7*/
public class StudentMapperTest {@Testpublic void testSelectBySex() {SqlSession sqlSession = SqlSessionUtil.openSession();StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);List<Student> students = mapper.selectBySex('女');students.forEach(student -> System.out.println(student));sqlSession.close();}@Testpublic void testSelectByBirth() throws ParseException {SqlSession sqlSession = SqlSessionUtil.openSession();StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");Date birth = simpleDateFormat.parse("2001-8-16");List<Student> students = mapper.selectByBirth(birth);students.forEach(student -> System.out.println(student));sqlSession.close();}@Testpublic void testSelectByName() {SqlSession sqlSession = SqlSessionUtil.openSession();StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);List<Student> names = mapper.selectByName("陈平安");System.out.println(names);sqlSession.close();}@Testpublic void testSelectById() {SqlSession sqlSession = SqlSessionUtil.openSession();StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);Student student = mapper.selectById(1L);System.out.println(student);sqlSession.close();}
}
