这里写自定义目录标题

• 1.新建maven项目
• 2.代码部分

1.新建maven项目

使用模板后一路next即可。


创建好后项目结构是这样的：

补上资源文件：

2.代码部分

2.0：前期准备（数据库建表）
创建一个student表：

写入数据：

导入包：

          <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <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>

2.1：编写实体Student类

2.2：编写mybatis-config.xml配置文件

<?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>
    <properties resource="dbconfig.properties"></properties>

<!--    <typeAliases>-->
<!--        <typeAlias type="com.zyq.pojo.Student" alias="Student"></typeAlias>-->
<!--    </typeAliases>-->

    <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"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="com/zyq/dao/StudentMapper.xml"/>
    </mappers>
</configuration>

2.3：编写dao层的StudentDao

package com.zyq.dao;

import com.zyq.pojo.Student;

import java.util.List;

public interface StudentDao {

//    查询所有学生的接口
//    后面的增删改查自行增加，方便起见这里只写一个查询
    public List<Student> selectStudents();


}

2.4：编写mapper层：StudentMapper.xml

<?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">
<!--  一个mapper对应一个接口
      里面写数据库语句，写完后还要在mybatis-config.xml绑定mapper
-->
<mapper namespace="com.zyq.dao.StudentDao">
    <select id="selectStudents" resultType="com.zyq.pojo.Student">
        select*from student
    </select>
</mapper>

2.5：编写Test测试类，查询数据

import com.zyq.dao.StudentDao;
import com.zyq.pojo.Student;
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 selectStu()  {

        System.out.println("查询所有学生的请求正在处理");
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            SqlSession sqlSession = sqlSessionFactory.openSession();
            StudentDao studentDao = sqlSession.getMapper(StudentDao.class);
            List<Student> student = studentDao.selectStudents();
            for (Student student1 : student) {
                System.out.println(student1);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2.6：测试成功与失败
测试成功：

出现bug：
出现bug的原因很可能是编译的时候，StudentMapper.xml没有注入到target中：
ps：这是成功注入的，如果只有StudentDao说明没有注入成功。

手动注入：
方法一：在pom.xml中添加资源适配，再次编译：

<build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                    <include>**/*.properties</include>
                </includes>
            </resource>

            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.xml</include>
                    <include>**/*.properties</include>
                </includes>
            </resource>
        </resources>
    </build>

方法二：在mybatis-config.xml中手动注入：

 <mappers>
        <mapper resource="com/zyq/dao/StudentMapper.xml"/>
    </mappers>

-----------------------------------------------------------------------------------------
到此结束，谢谢~