MyBatis学习笔记（一）创建第一个MyBatis项目

一、新建Maven项目

http://www.mybatis.org/mybatis-3/zh/index.html 该链接为MyBatis官方地址

创建MyBatis项目主要有两种办法，一种是导入jar包，可在github上下载https://github.com/mybatis/mybatis-3/releases。另一种方法就是现在比较常用的，也是官方推荐的maven导入。

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

下面我以IDEA来构建一个简单的MyBatis入门案例

 

无需选择任何模板直接next即可

直接next到finish即可

二、mybatis配置相关xml文件

pom.xml需要加上必须的MyBatis、junit、mysql连接驱动，这些都可以在maven官网上找到https://mvnrepository.com/

<?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.mybatis.demo</groupId>
    <artifactId>demo1</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.0</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.47</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
    </dependencies>


</project>

然后在main目录下的resources文件夹内新建mybatis-config.xml文件用来存放mybatis配置信息，和mapper文件夹用户存放映射文件

 下为mybatis-config.xml文件

<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis_test"/>
                <property name="username" value="root"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>
    <!--映射配置文件路径-->
    <mappers>
        <mapper resource="mapper/userMapper.xml"/>
    </mappers>
</configuration>

三、实现mybatis

我这里就使用navicat创建了一个简单的user表

 在IDEA中创建一个user实体类，并且生成getter setter方法

public class User {
    private int id;
    private String username;
    private String password;

    public int getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

编写userMapper映射文件

<?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">
<!--
    用于定义一个映射文件的根节点
    namespace属性是用来配置命名空间
    resultType是sql映射文件中定义返回值类型
-->
<mapper namespace="com.mybatis.demo.User">
    <select id="userList" resultType="com.mybatis.demo.User">
      select * from users
    </select>
</mapper>

编写测试类

import com.mybatis.demo.User;
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.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class myBatisTestDemo {
    @Test
    public void demo1(){
        try {
            //引入配置文件
            InputStream io=Resources.getResourceAsStream("mybatis-config.xml");
            //创建sqlSessionFactory对象
            SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(io);
            SqlSession sqlSession=sqlSessionFactory.openSession();
            List<User> lists=sqlSession.selectList("userList");
            System.out.println(lists.size());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}