Mybatis知識小結（一）

阿新 • • 發佈：2021-10-15

一、簡介

mybatis是一個基於Java持久層的框架，內部封裝JDBC使開發者只需關注SQL語句本身，而不需要花費時間去處理建立JDBC的繁瑣過程。

快速入門：

匯入相關jar包

<!--mybatis相關-->
<dependency>
  <groupId>org.mybatis</groupId>
  <artifactId>mybatis</artifactId>
  <version>3.4.5</version>
</dependency>
<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>5.1.6</version>
</dependency>

配置核心檔案：sqlMapperConfig.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>
  <!--載入properties檔案-->
  <properties resource="jdbc.properties"/>

  <!--定義實體別名-->
  <typeAliases>
    <package name="com.nanychuan.domin"/>
  </typeAliases>

  <!--配置環境-->
  <environments default="development">
    <environment id="development">
      <transactionManager type="jdbc"></transactionManager>
      <dataSource type="POOLED">
        <property name="driver" value="${jdbc.driver}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
      </dataSource>
    </environment>
  </environments>

  <!--載入對映檔案-->
  <mappers>
    <package name="com.nanychuan.mapper"/>
  </mappers>
</configuration>

配置對映檔案

<?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">
<mapper namespace="com.itheima.mapper.AccountMapper">
  <insert id="save" parameterType="account">
     insert into account values (#{id},#{name},#{money})
  </insert>

  <select id="findAll" parameterType="list" resultType="account">
     select * from account
  </select>
</mapper>

mapper 層：

package com.nanychuan.mapper;

import com.nanychuan.domin.Account;

import java.util.List;

/**
 * @author 往
 * save方法
 * findAll()方法
 */
public interface AccountMapper {
  public void save(Account account);

  public List<Account> findAll();
}

MapperTest

package com.nanychuan;

import com.itheima.domin.Account;
import com.itheima.mapper.AccountMapper;
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.io.InputStream;
import java.util.List;

public class MapperTest {
  @Test
  public void test1(){
    try {
      InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapperConfig.xml");
      SqlSessionFactory sqlSessionFactory = new                   SqlSessionFactoryBuilder().build(resourceAsStream);
      SqlSession sqlSession = sqlSessionFactory.openSession();
      AccountMapper mapper = sqlSession.getMapper(AccountMapper.class);
      List<Account> accountList = mapper.findAll();
      for (Account account : accountList) {
        System.out.println(account);
       }
      sqlSession.close();
     } catch (IOException e) {
      e.printStackTrace();
     }
   }
}

控制檯輸出：

Account{id=1, name='張三', money=10000.0} Account{id=2, name='張三', money=10000.0} Account{id=3, name='張三', money=10000.0}

註解實現：

mapper層：

package com.itheima.mapper;

import com.itheima.domin.Account;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;

import java.util.List;

/**
 * @author 往
 * save方法
 * findAll()方法
 */
public interface AccountMapper {
  @Insert("insert into account values(#{id},#{name},#{money})")
  public void save(Account account);

  @Select("select * from account")
  List<Account> findAll();
}

對映檔案：

<?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">
<mapper namespace="com.nanychuan.mapper.AccountMapper">
</mapper>