1.如何使用mybatis

• 創(chuàng)建user表誉尖，添加數(shù)據(jù)
• 創(chuàng)建模塊葱轩，導(dǎo)入坐標(biāo)
• 編寫My Batis核心配置文件
• 編寫sql映射文件
• 編碼
  • 定義pojo類
  • 加載核心配置文件，獲取SqlSessionFactory對(duì)象
  • 獲取SqlSession對(duì)象，執(zhí)行SQL語句
  • 釋放資源

1.創(chuàng)建user表缘圈，添加數(shù)據(jù)

測試代碼：

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.創(chuàng)建模塊，導(dǎo)入坐標(biāo)[導(dǎo)入測試包時(shí)袜蚕，還需要使用 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依賴 -->
    <dependency>
        <groupId>ch.qos.logback</groupId>
        <artifactId>logback-classic</artifactId>
        <version>1.2.3</version>
    </dependency>
    <!-- 添加logback-core依賴 -->
    <dependency>
        <groupId>ch.qos.logback</groupId>
        <artifactId>logback-core</artifactId>
        <version>1.2.3</version>
    </dependency>
    <!--mysql驅(qū)動(dòng)-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.26</version>
        <scope>compile</scope>
    </dependency>
    <!--junit單元測試-->
    <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 ：表示當(dāng)前的日志信息是可以輸出到控制臺(tái)的糟把。
    -->
    <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:用來設(shè)置打印級(jí)別，大小寫無關(guān)：TRACE, DEBUG, INFO, WARN, ERROR, ALL 和 OFF
     牲剃， 默認(rèn)debug
      <root>可以包含零個(gè)或多個(gè)<appender-ref>元素遣疯，標(biāo)識(shí)這個(gè)輸出位置將會(huì)被本日志級(jí)別控制。
      -->
    <root level="DEBUG">
        <appender-ref ref="Console"/>
    </root>
</configuration>

3.編寫mybatis-config.xml核心配置文件---（配置鏈接信息）

<?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. 編寫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:名稱空間
-->

<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. 編碼

• 定義pojo類

• 加載核心配置文件凿傅，獲取SqlSessionFactory對(duì)象

• 獲取SqlSession對(duì)象缠犀，執(zhí)行SQL語句

• 釋放資源

  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 快速入門代碼
   */
  public class MyBatisDemo {
  
      public static void main(String[] args) throws IOException {
  
          //1. 加載mybatis的核心配置文件数苫，獲取 SqlSessionFactory
          String resource = "mybatis-config.xml";
          InputStream inputStream = Resources.getResourceAsStream(resource);
          SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
  
          //2. 獲取SqlSession對(duì)象，用它來執(zhí)行sql
          SqlSession sqlSession = sqlSessionFactory.openSession();
          //3. 執(zhí)行sql
          List<User> users = sqlSession.selectList("text.selectAll");  
          System.out.println(users);
          //4. 釋放資源
          sqlSession.close();
  
      }
  }
  
  

  ---

優(yōu)化代碼使用Mapper代理（解決硬編碼問題辨液，簡化后期sql代碼）

• 定義新建與sql映射文件同名的mapper接口虐急，并將mapper接口和sql映射文件放置在同一目錄下（**在resources下新建層級(jí)目錄時(shí)使用com/user/mapper ” 斜杠 ” **）

• 設(shè)置sql映射文件:mybatis-config.xmlnamespace屬性為Mapper接口權(quán)限定名（小細(xì)節(jié)：后期如果有多個(gè)mapper文件，使用packing-name:com.bohai.mapper）

  <!--        加載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:中定義方法滔迈，方法名為SQL映射文件中sql語句的id止吁，并保持參數(shù)類型和返回值類型一致

  import com.itheima.pojo.User;
  
  import java.util.List;
  
  
  public interface UserMapper {
  
      List<User> selectAll();   //查詢user對(duì)象的selectAll()方法
  
      User selectById(int id);
  

• 編碼

  • 通過sqlSession的getMapper方法獲取Mapper接口的代理對(duì)象

    //3.1 獲取UserMapper接口的代理對(duì)象
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    

  • 調(diào)用對(duì)應(yīng)的方法，完成sql執(zhí)行

           List<User> users = userMapper.selectAll();
    

  • 完整代碼：

    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 代理開發(fā)
     */
    public class MyBatisDemo2 {
    
        public static void main(String[] args) throws IOException {
    
            //1. 加載mybatis的核心配置文件燎悍，獲取 SqlSessionFactory
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    
            //2. 獲取SqlSession對(duì)象敬惦，用它來執(zhí)行sql
            SqlSession sqlSession = sqlSessionFactory.openSession();
    
            //3. 獲取UserMapper接口的代理對(duì)象
            UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
            List<User> users = userMapper.selectAll();
    
            System.out.println(users);
            //4. 釋放資源
            sqlSession.close();
    
        }
    }