mybatis新手快速入门以及一些错误汇总_java

在这里插入图片描述

一、使用maven加载依赖

加载了连接数据库的依赖、mybatis的依赖以及lombok的依赖

<dependency>
  <groupId>junit</groupId>
  <artifactId>junit</artifactId>
  <version>4.11</version>
  <scope>test</scope>
 </dependency>

 <dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>5.1.47</version>
 </dependency>

 <dependency>
  <groupId>org.mybatis</groupId>
  <artifactId>mybatis</artifactId>
  <version>3.5.4</version>
 </dependency>
 <dependency>
  <groupId>org.projectlombok</groupId>
  <artifactId>lombok</artifactId>
  <version>1.18.12</version>
 </dependency>

二、建库、建表

在这里插入图片描述

三、配置MyBatis的配置文件（conf.xml）

<?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="com.mysql.jdbc.Driver" />
    <property name="url" value="jdbc:mysql://localhost:3306/数据库名字?/useUnicode=true&amp;characterEncoding=utf8&amp;useSSL=false" />
    <property name="username" value="root" />
    <property name="password" value="数据库密码" />
   </dataSource>
  </environment>
 </environments>

 
</configuration>

四、定义表所对应的实体类

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
 private Integer uid;
 private String uname;
 private String password;

}

五、定义操作表的sql的映射文件xxxMapper.xml

见名知意，操作的user表，所以映射文件也命名为了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">
<!--tuser是我自己定的名字-->
<mapper namespace="tuser">
 <!--id自己设置，等会调用方法名使用，resultType查询结果类型-->
 <select id="getUserById" resultType="com.hongda.space.entity.User">
  <!--sql语句，#{}是参数格式，注意字段要与实体类属性一致-->
  select * from t_user where uid=#{uid}
 </select>
 <!--parameterType参数类型-->
 <insert id="insertUser" parameterType="com.hongda.space.entity.User">
  insert into t_user(uname,password) values(#{uname},#{password});
 </insert>
</mapper>

六、在Mybatis配置文件中添加映射文件

将编写好的userMapper.xml添加到mybatis.xml配置文件，下方

<?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="com.mysql.jdbc.Driver" />
    <property name="url" value="jdbc:mysql://localhost:3306/数据库名字?/useUnicode=true&amp;characterEncoding=utf8&amp;useSSL=false" />
    <property name="username" value="root" />
    <property name="password" value="数据库密码" />
   </dataSource>
  </environment>
 </environments>

 <mappers>
  <mapper resource="mapper/userMapper.xml"/>
 </mappers>
</configuration>

七、编写增删改查代码测试

import com.hongda.space.entity.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.Reader;

/**
 * @ClassName Test01
 * @Description TODO
 * @Author whd
 * @Date 2021/3/19 14:45
 */
public class Test01 {
 public static void main(String[] args) throws IOException {
  //1.读取配置文件
  Reader reader = Resources.getResourceAsReader("conf.xml");
  //2.获取sqlSessionFactory
  SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);
  //3.获取sqlsession对象 执行sql
  SqlSession session = sessionFactory.openSession();
  //4.执行sql
  User user = session.selectOne("tuser.getUserById", 1);
  System.out.println(user);

  int i = session.insert("tuser.insertUser",new User(null, "小刘", "4545"));
  System.out.println(i+"------------");
  session.commit();
 }

}

结果：

在这里插入图片描述