MyBatis研究-编程知识

MyBatis研究

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 configurationPUBLIC "-//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mapperBlogMapper 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;@Overridepublic 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：