06MP-mybatis实现findAll方法

1、创建子模块

2、设置log4j的配置文件

log4j.rootLogger=DEBUG,A1
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=[%t] [%c]-[%p] %m%n

3、编写mybatis的全局配置文件： 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/mp"/>
                <property name="username" value="root"/>
                <property name="password" value="2000820."/>
            </dataSource>
        </environment>
    </environments>

    <!--定义映射sql语句的映射文件-->
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

4、创建user对象实体

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private int id;
    private String user_name;
    private String password;
    private String name;
    private int age;
    private String email;
}

5、编写UserMapper接口

public interface UserMapper {
    List<User> findAll();
}

6、编写UserMapper.xml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">
<mapper namespace="com.study.mapper.UserMapper">

    <select id="findAll" resultType="com.study.pojo.User">
        select * from tb_user
    </select>

</mapper>

7、编写test测试用例

@Test
  public void test() throws IOException {
      //加载mybatis核心配置文件
      String resource = "mybatis-config.xml";
      //获取输入流
      InputStream in = Resources.getResourceAsStream(resource);
      //获取sqlsessionFactory工厂
      SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
      //获取sqlsession
      SqlSession sqlSession = sqlSessionFactory.openSession();

      UserMapper mapper = sqlSession.getMapper(UserMapper.class);

      List<User> list = mapper.findAll();

      for (User user : list) {
          System.out.println(user);
      }
  }