项目结构

数据库表

引入依赖

<dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.30</version></dependency><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.5.5</version></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version><scope>test</scope></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version><scope>test</scope></dependency>

mybatis-config.xml 配置日志 数据源 映射

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!--    dddd--><settings><setting name="mapUnderscoreToCamelCase" value="ture"/><!--配置下划线转换为驼峰命名风格--><setting name="logImpl" value="STDOUT_LOGGING"/></settings><environments default="development"><environment id="development"><transactionManager type="JDBC"></transactionManager><!--事务管理器--><dataSource type="POOLED"><!--数据源 POOLED代表池化--><property name="driver" value="com.mysql.cj.jdbc.Driver"/><property name="url" value="jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&amp;useUnicode=true&amp;characterEncoding=UTF-8"/><property name="username" value="root"/><property name="password" value="root"/></dataSource></environment></environments><mappers><mapper resource="dao/StudentDao.xml"></mapper></mappers>
</configuration>

编写实体类

package com.tmg.domain;public class Student {private int id;private String name;private int age;//提供构造器private String email;//提供set()，get()，toString(),hascode()等方法public Student(int id, String name, int age, String email) {this.id = id;this.name = name;this.age = age;this.email = email;}public Student() {}public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}@Overridepublic String toString() {return "Student{" +"id=" + id +", name='" + name + '\'' +", age=" + age +", email='" + email + '\'' +'}';}
}

控制数据库数据方法

package com.tmg.dao;import com.tmg.domain.Student;
import org.apache.ibatis.annotations.Param;import java.util.List;public interface StudentDao {void insert(Student employee);void update(Student employee);void deleteById(Long id);List<Student> selectAll();Student selectById(Long id);//多个参数的配置void insertEmp( @Param("stuName")  String name,@Param("stuAge") int age, @Param("stuEmail")  String email);
}

StudentDao.xml

<?xml version="1.0" encoding="UTF-8" ?><!--指定约束文件：定义和限制当前文件中可以使用的标签和属性，以及标签出现的顺序
mybatis-3-mapper.dtd 约束文件名称
-->
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--映射的命名空间 = 包名+接口类-->
<mapper namespace="com.tmg.dao.StudentDao"><!--配置insert操作 id是方法名 parameterType是参数类型  #{属性名}用于读取对象的属性值--><!--#{}和${}的区别，#{}相当于PreparedStatement的占位符？提前编译，避免SQL注入 ${}是Statement字符串拼接，不能避免注入 --><!--获得最新的自增主键值 useGeneratedKeys=true keyProperty主键的属性--><insert id="insert" useGeneratedKeys="true" keyProperty="id" parameterType="com.tmg.domain.Student">insert into student( stu_id,stu_name,stu_age,stu_email) values (#{id},#{name},#{age},#{email});</insert><update id="update">update student set stu_age=#{age},stu_email=#{email},stu_name=#{name} where stu_id=#{id} ;</update><delete id="deleteById">delete from student where stu_id=#{id};</delete>
<!--    问题：查询出的名称为多个单词的字段出现null值-->
<!--    原因：数据库的字段单词以下划线分隔，Java的属性以驼峰命名，导致部分名称不一致无法实现映射--><select id="selectAll" resultType="com.tmg.domain.Student" resultMap="student">select * from student</select><resultMap id="student" type="com.tmg.domain.Student"><!--配置主键 property是java属性名 column是表字段名--><id property="id" column="stu_id" javaType="java.lang.Integer"></id><!--普通字段--><result property="name" column="stu_name"></result><result property="age" column="stu_age"></result><result property="email" column="stu_email"></result></resultMap><select id="selectById" resultType="com.tmg.domain.Student">select * from student where stu_id=#{id}</select><insert id="insertEmp">insert into student(stu_name,stu_age,stu_email) values (#{stuName},#{stuAge},#{stuEmail});</insert>
</mapper>

StudentDaoText 测试类

package com.tmg.dao;import com.tmg.domain.Student;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;import java.io.IOException;
import java.util.List;public class StudentDaoText {@Testpublic void testinsert() throws IOException {//创建会话工厂构建器SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();SqlSessionFactory factory = builder.build(Resources.getResourceAsStream("mybatis-config.xml"));//创建会话SqlSession sqlSession = factory.openSession();//获得Mapper对象StudentDao mapper = sqlSession.getMapper(StudentDao.class);//通过jdk动态代理创建实现类，返回代理对象Student student = new Student(0, "zzz", 20, "zzz@qq.com");mapper.insert(student);sqlSession.commit();System.out.println("insert--->"+student);}@Testpublic void testupdate() throws IOException {//创建会话工厂构建器SqlSessionFactoryBuilder factoryBuilder = new SqlSessionFactoryBuilder();SqlSessionFactory build = factoryBuilder.build(Resources.getResourceAsStream("mybatis-config.xml"));//创建会话SqlSession sqlSession = build.openSession();//获得Mapper对象StudentDao mapper = sqlSession.getMapper(StudentDao.class);Student student = new Student(12, "zl", 99, "zl@qq.com");mapper.update(student);sqlSession.commit();}@Testpublic void testdeleteById() throws IOException {SqlSessionFactoryBuilder factoryBuilder = new SqlSessionFactoryBuilder();SqlSessionFactory build = factoryBuilder.build(Resources.getResourceAsStream("mybatis-config.xml"));SqlSession sqlSession = build.openSession();StudentDao mapper = sqlSession.getMapper(StudentDao.class);mapper.deleteById(11L);sqlSession.commit();}@Testpublic void testselectAll() throws IOException {SqlSessionFactory build = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));SqlSession sqlSession = build.openSession();StudentDao mapper = sqlSession.getMapper(StudentDao.class);List<Student> students = mapper.selectAll();for(Student student : students){System.out.println(student);}}@Testpublic void testselectById() throws IOException {SqlSessionFactoryBuilder factoryBuilder = new SqlSessionFactoryBuilder();SqlSessionFactory factory = factoryBuilder.build(Resources.getResourceAsStream("mybatis-config.xml"));SqlSession sqlSession = factory.openSession();StudentDao mapper = sqlSession.getMapper(StudentDao.class);Student student = mapper.selectById(3L);System.out.println("student---->"+student);}@Testpublic void testinsertEmp() throws IOException {SqlSessionFactoryBuilder factoryBuilder = new SqlSessionFactoryBuilder();SqlSessionFactory factory = factoryBuilder.build(Resources.getResourceAsStream("mybatis-config.xml"));SqlSession sqlSession = factory.openSession();StudentDao mapper = sqlSession.getMapper(StudentDao.class);mapper.insertEmp("tmg",18,"tmg@qq.com");sqlSession.commit();}}