Mybatis学习第0节 -- 配置和使用

一、新建maven项目，方便框架导入

1. 在pom文件中添加依赖

<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.4.6</version>
</dependency>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.13</version>
</dependency>
<!-- https://mvnrepository.com/artifact/junit/junit -->
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.13-beta-1</version>
    <scope>test</scope>
</dependency>
<!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>2.11.1</version>
</dependency>

2. 导入改变 （Import Changes)

二、在resource文件夹下创建配置文件

0. 日志配置文件

log4j.rootLogger=DEBUG, stdout    

log4j.appender.stdout=org.apache.log4j.ConsoleAppender    
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout    
log4j.appender.stdout.layout.ConversionPattern=%d - %c -%-4r [%t] %-5p %c %x - %m%n    

1. 新建数据库配置文件db.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/book?serverTimezone=UTC&useUnicode=true&characterEncoding=utf8
jdbc.username=root
jdbc.password=

2.新建Mybatis配置文件mybatis-config.xml

1.导入数据库连接配置

    <!-- 导入数据库连接配置 -->
    <properties resource="db.properties"></properties>

2.定义数据源

设置事务管理器为JDBC，连接源类型为连接池，并且设置引用数据库连接配置中的变量

<!-- 定义数据源 -->
<environments default="development">
    <environment id="development">
        <!--配置事务管理器-->
        <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>

3.设置映射文件的配置

在package的name属性中指明mapper.xml文件所在的路径

<!-- 设置映射文件的包 -->
<mappers>
    <package name="io.github.coinsjack.mapper"></package>
</mapper

 

三、测试使用

项目结构,这里需要注意,如果想要将xml文件和java文件分离,就需要在recourse和java目录下建立相同的mapper目录结构,java里面写interface而resources里面写xml文件

 

1. pojo中创建我们的实体类Board

package io.github.coinsjack.pojo;

public class Board {

    private String user;
    private String time;
    private String message;

    public Board() {
    }

    public Board(String user, String time, String message) {
        this.user = user;
        this.time = time;
        this.message = message;
    }

    public void setUser(String user) {
        this.user = user;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    @Override
    public String toString() {
        return "Board{" +
                "user='" + user + '\'' +
                ", time='" + time + '\'' +
                ", message='" + message + '\'' +
                '}';
    }
}

 

2.编写接口BoardMapper  假设在这里我们随便取出一条记录

package io.github.coinsjack.dao;

import io.github.coinsjack.pojo.Board;


public interface BoardMapper {

    Board selectBoard();

}

3.编写mapper.xml文件

<?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="io.github.coinsjack.dao.BoardMapper">
    <select id="selectBoard" resultType="io.github.coinsjack.pojo.Board">
        SELECT * FROM board LIMIT 1;
    </select>
</mapper>

这里需要注意,将namespace指向对应的mapper接口类型, 而select标签中的id属性应当和接口中的方法名一致

4.编写工具类MyBatisUtil.java

1.准备好mybatis配置文件的路径名,可以从resource往下写

2.配置文件->InputStream->SqlSessionFactory->SqlSession

3.SqlSession就是我们想要的,通过它来获取Mapper

package io.github.coinsjack.util;

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 java.io.IOException;
import java.io.InputStream;

public class MyBatisUtil {

    private static SqlSessionFactory sqlSessionFactory = null;

    static {
        try {
            InputStream in = Resources.getResourceAsStream("mybatis-config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
}

5.编写测试类BoardMapperTest

package io.github.coinsjack.dao;

import io.github.coinsjack.util.MyBatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class BoardMapperTest {

    @Test
    public void testSelectBoard() {
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        BoardMapper boardMapper = sqlSession.getMapper(BoardMapper.class);
        System.out.println(boardMapper.selectBoard());
    }
}

到这里我们就可以访问到数据库中记录了