MyBatis入门案例（idea）

（一）创建maven项目并导入坐标
pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.selan</groupId>
    <artifactId>Mybatis-day01-easy</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <dependencies>
        <!--测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
        <!--mybatis依赖包-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.4</version>
        </dependency>
        <!--mysql依赖-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.11</version>
            <scope>runtime</scope>
        </dependency>
        <!--日志文件-->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
    </dependencies>
</project>

(二) 创建实体类和dao接口
user.java

public class User implements Serializable {
     
    private Integer id;
    private String username;
    private Date birthday;
    private String sex;
    private String address;

    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 Date getBirthday() {
     
        return birthday;
    }

    public void setBirthday(Date birthday) {
     
        this.birthday = birthday;
    }

    public String getSex() {
     
        return sex;
    }

    public void setSex(String sex) {
     
        this.sex = sex;
    }

    public String getAddress() {
     
        return address;
    }

    public void setAddress(String address) {
     
        this.address = address;
    }

    @Override
    public String toString() {
     
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", birthday=" + birthday +
                ", sex='" + sex + '\'' +
                ", address='" + address + '\'' +
                '}';
    }
}

dao接口

public interface IUserDao {
     
    /*
    * 查询所有操作
    * */
    List<User> findAll();
}

(三)创建mybatis主配置文件,
SqlMapConfig.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">
<!--Mybatis主配置文件-->
<configuration>
    <!--配置环境-->
    <environments default="mysql">
        <!--配置mysql的环境-->
        <environment id="mysql">
            <!--配置事务类型-->
            <transactionManager type="JDBC"></transactionManager>
            <!--配置数据源 ，也就是连接池-->
            <dataSource type="POOLED">
            <!--配置连接数据库的基本信息-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3300/eesy_mybatis"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <!--指定映射配置文件，，映射配置文件，指的是每个dao独立的配置文件-->
    <mappers>
        <mapper resource="com/selan/dao/IUserDao.xml"></mapper>
    </mappers>
</configuration>

(四)创建映射配置文件
注意：（1）位置必须与dao接口的包结构相同
（2）配置文件的mapper标签namespace属性的取值必须是dao接口的全限定类名
（3）映射配置文件的操作配置 id的取值必须是dao接口的方法名
总结：这样我们在开发中就无需再写dao的实现类了
IUserDao.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">
<mapper namespace="com.selan.dao.IUserDao">
    <!--配置查询所有-->
    <!--属性id为dao接口中的方法名-->
    <select id="findAll">
        select * from user
    </select>
</mapper>