2022.1.17-复习Mybatis基础使用

Mybatis官网
1.配置maven，导入依赖

<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.2</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
</dependency>
<!--在配置maven时,需注意maven静态资源问题过滤-->
<build>
<resources>
<resource>
<!--这里填写需解决过滤问题的路径（mapper.xml文件位置）-->
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
</resources>
</build>

2.创建实体类(pojo类) 例：

package com.hong.pojo;

public class User {

    private int id;
    private String name;
    private String pwd;
    //.......(set,get,tostring方法省略)
}

3.配置核心配置文件(可从官网获取)
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>

	<!--设置配置文件,在配置时需注意设置中的配置的位置问题-->
    <properties resource="db.properties"></properties>

    <!--建立别名，通过扫描包去获取全部-->
    <typeAliases>
        <package name="com.hong.pojo"/>
    </typeAliases>
    
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <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>
        <!--使用xml注册并使用sql-->
<!--    <mappers>-->
<!--        <package name="com.hong.dao"></package> -->
<!--    </mappers>-->
    	<!--使用注解注册并使用sql-->
<!--    <mappers>-->
<!--        <mapper class="com.hong.dao.UserMapper"></mapper> -->
<!--    </mappers>-->
   <!--使用包扫描的方式，进行集体注册,填写mapper文件所在路径 !!注意接口与其xml文件需要同名且在同一包下!!-->
   <mappers>
        <package name="com.hong.pojo"/>
   </mappers>
</configuration>

db.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis(这里填写自己的数据库名)?useSSL=false&useUnicode=true&characterEncoding=utf8
username=root
password=xxxxxx

配置工具类(在工具包下创建例:com.hong.utils下创建MyBatisUtils.java)

public class MybatisUtil {

    private static SqlSessionFactory sqlSessionFactory;

    static{
        try {
            //获取factorysession对象
            String resource = "mybatis-config.xml";//核心配置文件名
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory= new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    public static SqlSession getSqlSession(){
    	//里面设置ture为配置自动提交事务
        return  sqlSessionFactory.openSession(true);
    }
}

4.创建mapper接口与其xml文件
例子：
4.1配置UserMapper.java接口

public interface UserMapper {
    public List<User> userselect();
}

4.2配置对应xml文件UserMapper.xml(要同名)

<?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="com.hong.Mapper.UserMapper">
<!--注意上面填对对应的作用域-->
<!--该id需与接口中方法名一致-->
    <select id="userselect" resultType="user" >
        select * from user
    </select>
</mapper>

5.测试

public class Test {
    @Test
    public void test1(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> user = mapper.userselect();
        for(User user1:user){
            System.out.println(user1);
        }

    }
}

6.结果