回顾Mybatis

导入相关jar包

• junit
• mysql-connector-java
• mybatis
• spring-webmvc
• spring-jdbc
• aspectjweaver
• mybatis-spring

<dependencies>

    <!-- https://mvnrepository.com/artifact/junit/junit -->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.13</version>
        <scope>test</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.19</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.4</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>5.2.5.RELEASE</version>
    </dependency>
    <!--Spring操作数据库的话，还需要一个spring-jdbc-->
    <!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc</artifactId>
        <version>5.2.5.RELEASE</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.aspectj/aspectjweaver -->
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjweaver</artifactId>
        <version>1.9.5</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis-spring -->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis-spring</artifactId>
        <version>2.0.4</version>
    </dependency>

</dependencies>

编写实体类

Population.java

package com.kuang.pojo;

import lombok.Data;

/**
 * @author Administrator
 */
@Data
public class Population {
    private String city;
    private int total;
    private int male;
    private int female;
}

编写核心配置文件

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>

    <typeAliases>
        <package name="com.kuang.pojo"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/hello?useSSL=True"/>
                <property name="username" value="root"/>
                <property name="password" value="*****"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper class="com.kuang.mapper.PopulationMapper"/>
    </mappers>

</configuration>

编写接口

PopulationMapper.java

package com.kuang.mapper;

import com.kuang.pojo.Population;

import java.util.List;

/**
 * @author Administrator
 */
public interface PopulationMapper {
    /**
     * 查询用户
     * @return
     */
    public List<Population> selectPopulation();
}

编写mapper.xml文件

mapper与接口在同一目录下

PopulationMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.kuang.mapper.PopulationMapper">

    <select id="selectPopulation" resultType="population">
        select * from hello.pop_numbers;
    </select>

</mapper>

测试

import com.kuang.mapper.PopulationMapper;
import com.kuang.pojo.Population;
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 MyTest {

    @Test
    public void test1() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream in = Resources.getResourceAsStream(resource);

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        SqlSession sqlSession = sqlSessionFactory.openSession(true);

        PopulationMapper mapper = sqlSession.getMapper(PopulationMapper.class);
        List<Population> populations = mapper.selectPopulation();

        for (Population population : populations) {
            System.out.println(population);
        }        

    }

}

结果

Population(city=全    国, total=1332810869, male=682329104, female=650481765)
Population(city=北    京, total=19612368, male=10126430, female=9485938)
Population(city=天    津, total=12938693, male=6907091, female=6031602)
Population(city=河    北, total=71854210, male=36430286, female=35423924)
Population(city=山    西, total=35712101, male=18338760, female=17373341)
Population(city=内 蒙 古, total=24706291, male=12838243, female=11868048)
Population(city=辽    宁, total=43746323, male=22147745, female=21598578)
Population(city=吉    林, total=27452815, male=13907218, female=13545597)

注意点

在pom.xml配置maven静态资源过滤

<!--maven静态资源过滤-->
<build>
    <resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.xml</include>
            </includes>
            <filtering>true</filtering>
        </resource>
    </resources>
</build>

在mybatis核心配置文件中注册mapper

<mappers>
    <mapper class="com.kuang.mapper.PopulationMapper"/>
</mappers>