Mybatis学习(1)

 

 

 

 

1. 创建user表添加数据

2. 创建模块、导入坐标

    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.5</version>
    </dependency>

 
mysql的依赖:

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

junit测试依赖:

    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>

slf4j依赖

<!--    添加slf4j日志api-->
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>1.7.20</version>
    </dependency>

<dependency>
  <groupId>ch.qos.logback</groupId>
  <artifactId>logback-classic</artifactId>
  <version>1.2.3</version>
</dependency>

<dependency>
  <groupId>ch.qos.logback</groupId>
  <artifactId>logback-core</artifactId>
  <version>1.2.3</version>
</dependency>

logback依赖坐标完成后还需要logback.xml配置文件

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <!--
        CONSOLE ：表示当前的日志信息是可以输出到控制台的。
    -->
    <appender name="Console" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>[%level]  %cyan([%thread]) %boldGreen(%logger{15}) - %msg %n</pattern>
        </encoder>
    </appender>

    <logger name="com.itheima" level="DEBUG" additivity="false">
        <appender-ref ref="Console"/>
    </logger>


    <!--

      level:用来设置打印级别，大小写无关：TRACE, DEBUG, INFO, WARN, ERROR, ALL 和 OFF
     ， 默认debug
      <root>可以包含零个或多个<appender-ref>元素，标识这个输出位置将会被本日志级别控制。
      -->
    <root level="DEBUG">
        <appender-ref ref="Console"/>
    </root>
</configuration>

3. 编写mybatis的核心配置文件

url是MySQL在高版本需要指明是否进行SSL连接。

<?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"/>
<!--            数据连接信息-->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost/mybatis?useSSL=false"/>
                <property name="username" value="root"/>
                <property name="password" value=""/>
            </dataSource>

        </environment>
    </environments>
<!--    加载sql映射文件-->
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

4. 编写sql映射文件

namespace必须填写

<?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:名称空间
-->
<mapper namespace="test">
    <select id="selectAll" resultType="com.itheima.pojo.User">
        select * from tb_user;
    </select>
</mapper>

5. 编码

1. 定义实体类

package com.itheima.pojo;

public class User {
    private Integer id;
    private String username;
    private String password;
    private String gender;
    private String addr;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getAddr() {
        return addr;
    }

    public void setAddr(String addr) {
        this.addr = addr;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", gender='" + gender + '\'' +
                ", addr='" + addr + '\'' +
                '}';
    }
}

2. 加载核心配置文件，获取SqlSessionFactory对象

    //1.加载mybatis的核心配置文件,获取SqlSessionFactory
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

3.获取SqlSession对象，执行sql语句

  //2. 获取SqlSession对象，用它来执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //3.执行sql
        //这里的selectList里面的参数就是映射配置文件中的namespace.id，因为映射文件可能有多个Mapper所以，我们可以像包一样,用namespace.id。
        List<User> users = sqlSession.selectList("test.selectAll");
        System.out.println(users);

4. 释放资源

        sqlSession.close();