Mybatis入门-初步环境搭建

Mybatis开发环境搭建

1.引入依赖

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

    <dependency>
      <groupId>com.xzixi.framework</groupId>
      <artifactId>mybatis</artifactId>
      <version>2.2.2</version>
    </dependency>

    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.28</version>
    </dependency>
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2.创建核心配置文件mybatis-config.xml

声明:配置文件的名字叫什么都可以

<?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>

    <!--核心环境-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
<!--                &amp;代表&因为是特殊字符-->
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/test?characterEncoding=utf8&amp;useUnicode=true&amp;useSSL=false&amp;serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <!--映射文件-->
    <mappers>
        <mapper resource="org/mybatis/example/BlogMapper.xml"/>
    </mappers>
</configuration>
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3.创建数据库对应的表

CREATE TABLE IF NOT EXISTS student
(
	sid CHAR(8) PRIMARY KEY,
	sname VARCHAR(4) NOT NULL,
	sage TINYINT NOT NULL,
	sphone CHAR(11) NOT NULL UNIQUE
)
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4.创建pojo实体类

实体类的字段必须和表中字段一致，因为mybatis底层基于反射

package com.raoqi.pojo;

/**
 * @author rqq
 * @create 2022/7/3
 */
public class Student {
    private String sid;
    private String sname;
    private Byte sage;
    private String sphone;

    @Override
    public String toString() {
        return "Student{" +
                "sid='" + sid + '\'' +
                ", sname='" + sname + '\'' +
                ", sage=" + sage +
                ", sphone='" + sphone + '\'' +
                '}';
    }

    public String getSid() {
        return sid;
    }

    public void setSid(String sid) {
        this.sid = sid;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public Byte getSage() {
        return sage;
    }

    public void setSage(Byte sage) {
        this.sage = sage;
    }

    public String getSphone() {
        return sphone;
    }

    public void setSphone(String sphone) {
        this.sphone = sphone;
    }
}

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####5.创建Dao层接口(也叫mapper层)

package com.raoqi.mapper;

/**
 * @author rqq
 * @create 2022/7/3
 */
public interface StudentMapper {

    /**
     * 增删改统一返回int代表影响行数
     */
    int addStudent();
}

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####6.创建接口的映射配置文件，建议配置文件名字和接口名字保持一致

<?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="要映射哪个dao层接口">
    <select id="这个接口中的方法">
        具体的sql语句
    </select>

</mapper>
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7.在核心配置文件中引入映射配置文件

 <!--映射文件-->
    <mappers>
        <mapper resource="mappers/StudentMapper.xml"/> 
    </mappers>
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8.测试环境是否执行正常

public class MyBatisTest {

    @Test
    public void test() throws IOException {
        //获取核心配置文件得输入流
        InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
        //获取sqlsession构建者对象
        SqlSessionFactoryBuilder buider = new SqlSessionFactoryBuilder();
        //使用文件输入流构建sqlsession工厂
        SqlSessionFactory factory = buider.build(is);
        //使用工厂获取会话对象
        SqlSession sqlSession = factory.openSession();//默认不自动提交事务，传入true可以自动提交
        //使用接口字节码对象获取实例 它内部会动态代理创建mapper得子类
        StudentMapper mapper = sqlSession.getMapper(StudentMapper.class);
        mapper.addStudent();
		//提交事务
        sqlSession.commit();


    }
}
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mybatis框架的执行过程

1.读取核心配置文件mybatis.config.xml

2.找到配置文件中指定的映射文件

3.根据映射文件的namespace找到dao层接口

4.根据映射文件中的配置的标签id找到对应的方法并且执行里面的sql语句