今天完成的任务：写了mybatis，在同学帮助下解决了空指针的问题。

<?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="jdbc.properties"/>
    <typeAliases>
        <package name="entity"/>
        <!--<typeAlias type="entity.Student" alias="Student"></typeAlias>-->
    </typeAliases>
    <environments default="mybatis=demo">
        <environment id="mybatis=demo">
            <transactionManager type="JDBC"></transactionManager>
            <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>
    <mappers>
        <!--<mapper resource="StudentMapper.xml"></mapper>-->
        <package name="dao"/>
    </mappers>
</configuration>

package dao;

import entity.Student;

import java.util.List;

public interface StudentMapper {
    int insertStudent(Student student);
    Student selectOneById(int id);
    List<Student> selectAllStudent();

}

package entity;

public class Student {
    private Integer id;
    private String name;
    private Integer age;
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) { this.name = name; }

    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }

}

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="dao.StudentMapper">
    <resultMap id="studentMapper" type="entity.Student">
        <result property="id" column="id"/>
        <result property="name" column="name"/>
        <result property="age" column="age"/>
    </resultMap>

    <insert id="insertStudent" parameterType="entity.Student">
        INSERT INTO student (id,name,age) VALUES (#{id},#{name},#{age})
    </insert>

</mapper>

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test
jdbc.username=root
jdbc.password=6546

运行下面的程序出现了空指针

import dao.StudentMapper;
        import entity.Student;
        import org.apache.ibatis.session.SqlSession;
        import org.apache.ibatis.session.SqlSessionFactory;
        import org.apache.ibatis.session.SqlSessionFactoryBuilder;

        import java.io.InputStream;


public class Main {
    public static void main(String[] args) throws Exception {
        InputStream in = Main.class.getResourceAsStream("mybatis-cfg.xml");
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        SqlSession session = factory.openSession();

        StudentMapper mapper = session.getMapper(StudentMapper.class);
        Student student = new Student();
        student.setName("like");
        student.setId(42);
        student.setAge(25);
        mapper.insertStudent(student);
        session.commit();
        session.close();
    }
}

我的文件结构是这样的：

解决方法用maven工程，把我创建的resource里的文件都挪到maven自带的resources里，然后稍作改动，就解决了。

一会我去看看log4j。尽量点亮技能树。

遇到的问题：解决了mybatis里空指针问题。

明天的计划：完成任务1.25.并点亮log4j技能。