MyBatis —— HelloWold

1、先准备例子中的表结构

create table `tbl_employee`( 
    `id` int(11) primary key auto_increment, 
    `last_name` varchar(255) not null ,
    `gender` char(1) not null,
    `email` varchar(255) not null
);

2、创建maven+spring+springmvc项目，pom文件中需要注入mybatis-spring的依赖，mybatis-spring2.0与Spring 框架5.0兼容

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis-spring</artifactId>
    <version>2.0.4</version>
</dependency>

 <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.4</version>
</dependency>

3、创建Mybatis全局配置文件

全局配置文件：包含数据库连接池信息，事务管理器信息等...系统运行环境信息

<?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>
    <!-- mybatis 可以使用properties来引入外部peoperties配置文件的内容
        resource:引入类路径下的资源
        url:除此之外还可以使用url引入网络路径或者磁盘下的资源-->
    <properties resource="dbconfig.properties"/>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 将EmployeeMapper.xml注册到全局配置文件中-->
    <mappers>
        <mapper resource="mapper/EmployeeMapper.xml"/>
    </mappers>
</configuration>

4、创建数据源文件

jdbc.driver = com.mysql.jdbc.Driver
jdbc.url = jdbc:mysql://localhost:3306/mybatis?useUnicode=true&useSSL=false
jdbc.username = root
jdbc.password = abcd123456

5、创建javabean

package com.sangyu.bean;

public class Employee {
    private Integer id;
    private String lastName;
    private String email;
    private String gender;

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

    public void setEmail(String email) {
        this.email = email;
    }

    public String getEmail() {
        return email;
    }

    public Integer getId() {
        return id;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

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

    public String getGender() {
        return gender;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", lastName='" + lastName + '\'' +
                ", email='" + email + '\'' +
                ", gender='" + gender + '\'' +
                '}';
    }

    public Employee(Integer id,String lastName,String email,String gender){
        this.email = email;
        this.lastName = lastName;
        this.id = id;
        this.gender = gender;
    }
    public Employee(){
    }
}

6、创建 mapper 接口

public interface EmployeeMapper {
    Employee getEmpId(int id);
}

7、创建EmployeeMapper.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">
<!--namespace：因为没有对应mapper这里的名字可以任意起-->
<mapper namespace="com.sangyu.mapper.EmployeeMapper">
    <!--
    id:唯一标识
    resultType:返回值类型，对应的Bean类型
    {#id}：从传递过来的参数中取出id值-->
    <select id="getEmpId" resultType="com.sangyu.bean.Employee">
    select * from tbl_employee where id = #{id}
  </select>
</mapper>

8、创建test

public class MyBatisTest {
    @Test
    public void Test() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); // 根据xml创建sqlSessionFactory
        SqlSession session = sqlSessionFactory.openSession(); // 2. 从 SqlSessionFactory 中获取 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
        Employee employee = session.selectOne("com.sangyu.mapper.EmployeeMapper.getEmpId",1); // selectOne需要传递2个参数，第一个参数是mapper.xml中的namespace+select中的id，第二是需要sql中需要查询的参数
        System.out.println(employee);
    }
}