入门级使用

参照MyBatis官网的简介与入门部分，尝试使用MyBatis，可创建新的Maven项目，引入以下依赖：

<dependencies>       
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.8</version>
    </dependency>

    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.49</version>
    </dependency>
</dependencies>

其中，mysql-connector-java用于进行连接MySQL。

然后在项目resources目录下创建配置文件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>
    <!--    加载配置文件-->
    <properties resource="config.properties"/>
    <!-- 和spring整合后 environments配置将废除 -->
    <environments default="development">
        <environment id="development">
            <!-- 使用jdbc事务管理 -->
            <transactionManager type="JDBC"/>
            <!-- 数据库连接池 -->
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <!-- 加载mapper.xml -->
    <mappers>
        <!-- mapper文件 -->
        <mapper resource="mapper/BlogMapper.xml"></mapper>
    </mappers>
</configuration>

其中涉及到一个变量配置文件config.properties以及一个生成的mapper xml文件：

config.properties（放入resources/下）配置内容如下：

username=root
password=123456
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/demo01?characterEncoding=utf8

mapper xml（放入resources/mapper/下）内容如下：

<?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="org.example.mapper.BlogMapper">
    <select id="selectBlog" parameterType="Integer" resultType="org.example.pojo.Blog">
        select * from blog WHERE id =#{id}
    </select>
</mapper>

编写运行主类，具体代码如下：

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.example.mapper.BlogMapper;
import org.example.pojo.Blog;

import java.io.InputStream;


public class MybatisDemo01 {
    public static void main(String[] args) throws Exception {
        // 装载mybatis配置文件
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        // 创建sql会话工厂
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        // Blog blog = session.selectOne("org.example.mapper.BlogMapper.selectBlog", 1);
        // 获取mapper
        BlogMapper blogMapper = session.getMapper(BlogMapper.class);
        Blog blog = blogMapper.selectBlog(1);
        System.out.println(blog);
    }
}

其中，涉及到的Java类包括：

•  Pojo类：Blog.java，映射数据库Schema。类与DDL分别如下：

package org.example.pojo;


public class Blog {
    private Integer id;
    private String name;

    @Override
    public String toString() {
        return "Blog{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

DDL：

CREATE TABLE blog(id INT,name VARCHAR(20));

插入一条测试数据：

INSERT INTO blog(id, name)VALUES(1,'Jordan');

• Mapper接口：BlogMapper.java

package org.example.mapper;

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;
import org.example.pojo.Blog;


public interface BlogMapper {
// 注解或xml文件配置，两种方式均可
//    @Select("SELECT * FROM blog WHERE id=#{id}")
    Blog selectBlog(int id);
}

运行主类，结果：