mybatis新手快速入门以及一些错误汇总

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

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：

一些错误

编写中可能碰到的错误

1.mapped statements collection does not contain…

2.the server time zone value’xxxxxxxxx’ is…

在mybatis配置文件中的jdbc连接地址后面拼接servertimezone=asia/shanghai

总结 

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