1.如何使用mybatis
- 创建user表，添加数据
- 创建模块，导入坐标
- 编写My Batis核心配置文件
- 编写sql映射文件
- 编码
- 定义pojo类
- 加载核心配置文件，获取SqlSessionFactory对象
- 获取SqlSession对象，执行SQL语句
- 释放资源
1.创建user表，添加数据
测试代码：
create database mybatis;
use mybatis;
drop table if exists tb_user;
create table tb_user(
id int primary key auto_increment,
username varchar(20),
password varchar(20),
gender char(1),
addr varchar(30)
);
INSERT INTO tb_user VALUES (1, 'zhangsan', '123', '男', '北京');
INSERT INTO tb_user VALUES (2, '李四', '234', '女', '天津');
INSERT INTO tb_user VALUES (3, '王五', '11', '男', '西安');
2.创建模块，导入坐标[导入测试包时，还需要使用 logback.xml 配置文件]
<!--servlet-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
<scope>provided</scope>
</dependency>
<!-- 添加slf4j日志api -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.20</version>
</dependency>
<!-- 添加logback-classic依赖 -->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
</dependency>
<!-- 添加logback-core依赖 -->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
<version>1.2.3</version>
</dependency>
<!--mysql驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.26</version>
<scope>compile</scope>
</dependency>
<!--junit单元测试-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13</version>
<scope>test</scope>
</dependency>
<dependency>
<!--mybatis-->
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>x.x.x</version>
</dependency>
<!--logback.xml文件-->
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<!--
CONSOLE ：表示当前的日志信息是可以输出到控制台的。
-->
<appender name="Console" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<pattern>[%level] %blue(%d{HH:mm:ss.SSS}) %cyan([%thread]) %boldGreen(%logger{15}) - %msg %n</pattern>
</encoder>
</appender>
<logger name="com.itheima" level="DEBUG" additivity="false">
<appender-ref ref="Console"/>
</logger>
<!--
level:用来设置打印级别，大小写无关：TRACE, DEBUG, INFO, WARN, ERROR, ALL 和 OFF
， 默认debug
<root>可以包含零个或多个<appender-ref>元素，标识这个输出位置将会被本日志级别控制。
-->
<root level="DEBUG">
<appender-ref ref="Console"/>
</root>
</configuration>
3.编写mybatis-config.xml核心配置文件---（配置链接信息）
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="org/mybatis/example/BlogMapper.xml"/>
</mappers>
</configuration>
4. 编写sql映射文件userMapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--
namespace:名称空间
-->
<mapper namespace="text">
<select id="selectAll" resultType="com.itheima.pojo.User">
select *
from tb_user;
</select>
<select id="selectById" resultType="user">
select *
from tb_user where id = #{id};
</select>
</mapper>
5. 编码
定义pojo类
加载核心配置文件，获取SqlSessionFactory对象
获取SqlSession对象，执行SQL语句
-
释放资源
package com.itheima; import com.itheima.pojo.User; 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; import java.util.List; /** * Mybatis 快速入门代码 */ public class MyBatisDemo { public static void main(String[] args) throws IOException { //1. 加载mybatis的核心配置文件，获取 SqlSessionFactory String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); //2. 获取SqlSession对象，用它来执行sql SqlSession sqlSession = sqlSessionFactory.openSession(); //3. 执行sql List<User> users = sqlSession.selectList("text.selectAll"); System.out.println(users); //4. 释放资源 sqlSession.close(); } }
优化代码使用Mapper代理（解决硬编码问题，简化后期sql代码）
定义新建与sql映射文件同名的mapper接口，并将mapper接口和sql映射文件放置在同一目录下（**在resources下新建层级目录时使用com/user/mapper ” 斜杠 ” **）
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设置sql映射文件:mybatis-config.xmlnamespace属性为Mapper接口权限定名（小细节：后期如果有多个mapper文件，使用packing-name:com.bohai.mapper）
<!-- 加载sql映射文件--> <mapper resource="com/itheima/mapper/UserMapper.xml"/> <!--Mapper代理方式--> <!-- <package name="com.itheima.mapper"/>-->
-
在Mapper接口:large_blue_circle:中定义方法，方法名为SQL映射文件中sql语句的id，并保持参数类型和返回值类型一致
import com.itheima.pojo.User; import java.util.List; public interface UserMapper { List<User> selectAll(); //查询user对象的selectAll()方法 User selectById(int id); -
编码
-
通过sqlSession的getMapper方法获取Mapper接口的代理对象
//3.1 获取UserMapper接口的代理对象 UserMapper userMapper = sqlSession.getMapper(UserMapper.class); -
调用对应的方法，完成sql执行
List<User> users = userMapper.selectAll(); -
完整代码：
package com.itheima; import com.itheima.mapper.UserMapper; import com.itheima.pojo.User; 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; import java.util.List; /** * Mybatis 代理开发 */ public class MyBatisDemo2 { public static void main(String[] args) throws IOException { //1. 加载mybatis的核心配置文件，获取 SqlSessionFactory String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); //2. 获取SqlSession对象，用它来执行sql SqlSession sqlSession = sqlSessionFactory.openSession(); //3. 获取UserMapper接口的代理对象 UserMapper userMapper = sqlSession.getMapper(UserMapper.class); List<User> users = userMapper.selectAll(); System.out.println(users); //4. 释放资源 sqlSession.close(); } }
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