Mybatis 01

搭建环境

1、创建maven项目

2、在pom.xml文件中导入

    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.4.6</version>
    </dependency>

    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.26</version>
    </dependency>

3、编写mybatis的核心配置文件mybatis-config.xml

 mybatis-config.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.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useUnicode=true&amp;characterEncoding=utf8&amp;serverTimezone=GMT%2B8&amp;useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value="12345"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
<!--        注意改为实现dao层UserDao接口类的xml文件-->
        <mapper resource="com/lu/dao/UserMapper.xml"/>
    </mappers>
</configuration>

4、

• 编写MybatisUtils工具类

• package com.lu.utils;
  
  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;
  
  public class MybatisUtils {
  
      private static SqlSessionFactory sqlSessionFactory;
  
      static {
  
          try {
              //第一步： 获取sqlSessionFactory对象
              String resource = "mybatis-config.xml";
              InputStream inputStream = Resources.getResourceAsStream(resource);
              sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
  
          } catch (IOException e) {
              e.printStackTrace();
          }
      }
  
      //既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例。
      // SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句。
      public static SqlSession getSqlSession(){
          SqlSession sqlSession = sqlSessionFactory.openSession();
          return sqlSession;
      }
  }
  

  5、根据数据库的表编写实体类User

• 

  package com.lu.pojo;
  
      //实体类
  public class User {
      private int id;
      private String name;
      private String pwd;
  
      public User() {
  
      }
  
      public User(int id, String name, String pwd) {
          this.id = id;
          this.name = name;
          this.pwd = pwd;
      }
  
      public int getId() {
          return id;
      }
  
      public void setId(int id) {
          this.id = id;
      }
  
      public String getName() {
          return name;
      }
  
      public void setName(String name) {
          this.name = name;
      }
  
      public String getPwd() {
          return pwd;
      }
  
      public void setPwd(String pwd) {
          this.pwd = pwd;
      }
  
      @Override
      public String toString() {
          return "User{" +
                  "id=" + id +
                  ", name='" + name + '\'' +
                  ", pwd='" + pwd + '\'' +
                  '}';
      }
  }
  

  6、创建编写dao层接口类UserDao

• package com.lu.dao;
  
  import com.lu.pojo.User;
  
  import java.util.List;
  
  public interface UserDao {
      List<User> getUserList();
  }

  7、编写实现接口类的UserMapper.xml配置文件

• <?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=绑定一个对应的Dao/Mapper接口-->
  <mapper namespace="com.lu.dao.UserDao">
  <!--    查询语句-->
      <select id="getUserList" resultType="com.lu.pojo.User">
          select * from mybatis.user
      </select>
  
  </mapper>

  8、测试：在test中编写测试类UserDaoTest

• 

  测试类 UserDaoTest

  package com.lu.dao;
  
  import com.lu.pojo.User;
  import com.lu.utils.MybatisUtils;
  import org.apache.ibatis.session.SqlSession;
  import org.junit.Test;
  
  import java.util.List;
  
  public class UserDaoTest {
      @Test
      public void test(){
          //第一步：获得SqlSession对象
          SqlSession sqlSession = MybatisUtils.getSqlSession();
  
          //方式一：getMapper
          UserDao userDao = sqlSession.getMapper(UserDao.class);
          List<User> userList = userDao.getUserList();
  
          for (User user : userList) {
              System.out.println(user);
          }
  
          //关闭SqlSession
          sqlSession.close();
  
      }
  
  }
  

  最后注意在pom.xml文件中写入

•   <build>
      <resources>
        <resource>
          <directory>src/main/resources</directory>
          <includes>
            <include>**/*.properties</include>
            <include>**/*.xml</include>
          </includes>
          <filtering>true</filtering>
        </resource>
        <resource>
          <directory>src/main/java</directory>
          <includes>
            <include>**/*.properties</include>
            <include>**/*.xml</include>
          </includes>
          <filtering>true</filtering>
        </resource>
      </resources>
    </build>