创建数据库

语句要分别执行

CREATE DATABASE mybatis;USE mybatis;CREATE TABLE `user`(id INT(10) NOT NULL PRIMARY KEY,`name` VARCHAR(20) DEFAULT NULL,INSERT INTO `user`(id,`name`,pwd)  VALUES
(1,'张三','123456'),
(2,'李四','121212'),
(3,'王五','1314520')

搭配环境

1、在pojo包创建实体类User

2、创建一个工具类utils，用来获取SqlSession实例

3、在resources资源下面创建一个mybatis-config.xml文件，并绑定UserMapper.xml或UserMapper接口

4、在dao包下创建UserMapper接口和创建UserMapper.xml文件

实体类User，使用注解需要导入lombok的依赖包

package com.qing.pojo;import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {private int id;private String name;private String pwd;}

工具类MyUtils

package com.qing.utils;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 java.io.IOException;
import java.io.InputStream;public class MyUtils {private static SqlSessionFactory sqlSessionFactory;static {try{String resources="mybatis-config.xml";InputStream inputStream= Resources.getResourceAsStream(resources);sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);} catch (IOException e) {throw new RuntimeException(e);}}public static SqlSession getSqlSession(){return sqlSessionFactory.openSession();}
}

mybatis-config.xml配置文件

<?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><environments default="test"><environment id="test"><transactionManager type="JDBC"></transactionManager><dataSource type="POOLED"><property name="driver" value="com.mysql.jdbc.Driver"/><property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&amp;useUnicode=true&amp;characterEcoding=uft-8"/><property name="username" value="root"/><property name="password" value="123456"/></dataSource></environment></environments><mappers><mapper class="com.qing.dao.UserMapper"></mapper></mappers>
</configuration>

会遇到资源过滤问题，需要将build导入在pom.xml中

  <build><resources><resource><directory>src/main/resources</directory><includes><include>**/*.properties</include><include>**/*.xml</include></includes><filtering>true</filtering></resource><resource><directory>src/main/java</directory><includes><include>**/*.properties</include><include>**/*.xml</include></includes><filtering>true</filtering></resource></resources></build>

增加数据

UserMapper接口

package com.qing.dao;import com.qing.pojo.User;public interface UserMapper {int addUser(User user);}

UserMapper.xml

<?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.qing.dao.UserMapper"><insert id="addUser">insert into user(id,name,pwd) values (#{id},#{name},#{pwd})</insert>
</mapper>

测试，测试使用注解需要导入Junit依赖

package com.qing;import com.qing.dao.UserMapper;
import com.qing.pojo.User;
import com.qing.utils.MyUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;public class MyBatisTest {@Testpublic void test(){SqlSession sqlSession = MyUtils.getSqlSession();UserMapper mapper = sqlSession.getMapper(UserMapper.class);int i = mapper.addUser(new User(4, "安安", "238421"));if(i>0){System.out.println("插入成功");}sqlSession.commit();sqlSession.close();}}

删除数据

UserMapper接口

package com.qing.dao;public interface UserMapper {int deleteUser(int user);}

UserMapper.xml

<?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.qing.dao.UserMapper"><delete id="deleteUser">delete from user where id=#{id}</delete>
</mapper>

测试

package com.qing;import com.qing.dao.UserMapper;
import com.qing.utils.MyUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;public class MyBatisTest {@Testpublic void test(){SqlSession sqlSession = MyUtils.getSqlSession();UserMapper mapper = sqlSession.getMapper(UserMapper.class);int i = mapper.deleteUser(4);if(i>0){System.out.println("删除成功");}sqlSession.commit();sqlSession.close();}}

修改数据

UserMapper.xml

<?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.qing.dao.UserMapper"><update id="updateUser">update user set name=#{name},pwd=#{pwd} where id=#{id}</update>
</mapper>

UserMapper接口

package com.qing.dao;import com.qing.pojo.User;public interface UserMapper {int updateUser(User user);}

测试

package com.qing;import com.qing.dao.UserMapper;
import com.qing.pojo.User;
import com.qing.utils.MyUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;public class MyBatisTest {@Testpublic void test(){SqlSession sqlSession = MyUtils.getSqlSession();UserMapper mapper = sqlSession.getMapper(UserMapper.class);int i = mapper.updateUser(new User(4,"hh","82390"));if(i>0){System.out.println("修改成功");}sqlSession.commit();sqlSession.close();}}

查询数据

UserMapper接口，查询所有数据

package com.qing.dao;import com.qing.pojo.User;import java.util.List;public interface UserMapper {List<User> queryAllUser();}

UserMapper.xml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.qing.dao.UserMapper"><select id="queryAllUser" resultType="com.qing.pojo.User">select * from user</select>
</mapper>

测试

package com.qing;import com.qing.dao.UserMapper;
import com.qing.pojo.User;
import com.qing.utils.MyUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;import java.util.List;public class MyBatisTest {@Testpublic void test(){SqlSession sqlSession = MyUtils.getSqlSession();UserMapper mapper = sqlSession.getMapper(UserMapper.class);List<User> userList = mapper.queryAllUser();for (User user : userList) {System.out.println(user);}}}

如果需要查询一条语句，给点一个条件即可，参数传入主键id，并在UserMapper.xml中的select语句中加上where  id=#{id}

总结：

1、查询所以数据，插入数据，修改数据，参数是一个对象；

2、根据id查询，删除数据，参数是一个基本类型

3、查询不需要提交事务，增删改查需要提交数据，否则，数据不会成功更新到数据库

4、查询的数据类型是一个User，增删改数据类型是int，因为查询查的是数据，一条数据就是一个对象，增删改执行成功就会返回"受影响行数为1"

原理：获取sqlSession实例，通过getMapper反射到UserMapper接口，就可以获取接口中的方法，接口中的方法又和UserMapper.xml绑定，就可以查询数据库语句；数据库的连接交给了mybatis-config.xml配置文件，获取sqlSession实例交给了MyBatis工具类