mybatis学习（一）一个在idea下的实例

时间：2023-03-09 19:20:53
mybatis学习（一）一个在idea下的实例

今天总结的是mybatis，首先说mybatis是什么？

MyBatis 是一个简化和实现了 Java 数据持久化层(persistence layer)的开源框架，它抽象了大量的 JDBC 冗余代 码，并提供了一个简单易用的 API 和数据库交互。 MyBatis 的前身是 iBATIS，iBATIS 于 2002 年由 Clinton Begin 创建。MyBatis 3 是 iBATIS 的全新设计，支持 注解和 Mapper。

而 MyBatis 流行起来有以下原因：

 它消除了大量的 JDBC 冗余代码

 它有低的学习曲线

 它能很好地与传统数据库协同工作

 它可以接受 SQL 语句

 它提供了与 Spring 和 Guice 框架的集成支持

 它提供了与第三方缓存类库的集成支持

 它引入了更好的性能

下面介绍一个mybatis的小例子：

使用 MyBatis 开发一个简单的 Java 项目：大致步骤如下

 新建表 STUDENTS，插入样本数据

 新建一个 Java 项目，将 MyBatis-3.2.2.jar 添加到 classpath 中

 新建建 MyBatisSqlSessionFactory 单例模式类

 新建映射器 StudentMapper 接口和 StudentService 类

 新建一个 JUnit 测试类来测试 StudentService

①我使用的是mysql，首先新建一个数据库mybatis1，再新建表STUDENTS

CREATE TABLE STUDENTS

(

stud_id int(11) NOT NULL AUTO_INCREMENT,

name varchar(50) NOT NULL,

email varchar(50) NOT NULL,

dob date DEFAULT NULL,

PRIMARY KEY (stud_id)

) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=latin1;

/*Sample Data for the students table */

insert into students(stud_id,name,email,dob)

values (1,'Student1','student1@gmail.com','1983-06-25');

insert into students(stud_id,name,email,dob)

values (2,'Student2','student2@gmail.com','1983-06-25');

②我新建的是maven项目，导入jar包在pom.xml中进行了配置

 <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/maven-v4_0_0.xsd">

   <modelVersion>4.0.0</modelVersion>

   <groupId>com.bai</groupId>

   <artifactId>bai</artifactId>

   <packaging>war</packaging>

   <version>1.0-SNAPSHOT</version>

   <name>bai Maven Webapp</name>

   <url>http://maven.apache.org</url>

   <dependencies>

     <dependency>

       <groupId>junit</groupId>

       <artifactId>junit</artifactId>

       <version>3.8.1</version>

       <scope>test</scope>

     </dependency>

     <dependency>

       <groupId>org.mybatis</groupId>

       <artifactId>mybatis</artifactId>

       <version>3.2.2</version>

       <scope>test</scope>

     </dependency>

     <dependency>

       <groupId>mysql</groupId>

       <artifactId>mysql-connector-java</artifactId>

       <version>5.1.22</version>

       <scope>runtime</scope>

     </dependency>

     <dependency>

       <groupId>org.slf4j</groupId>

       <artifactId>slf4j-api</artifactId>

       <version>1.7.5</version>

       <scope>test</scope>

     </dependency>

     <dependency>

       <groupId>org.slf4j</groupId>

       <artifactId>slf4j-log4j12</artifactId>

       <version>1.7.5</version>

       <scope>runtime</scope>

     </dependency>

     <dependency>

       <groupId>log4j</groupId>

       <artifactId>log4j</artifactId>

       <version>1.2.17</version>

       <scope>runtime</scope>

     </dependency>

   </dependencies>

   <build>

     <finalName>bai</finalName>

   </build>

 </project>

③ 新建 log4j.properties 文件，添加到 classpath 中.

log4j.rootLogger=DEBUG, stdout

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

log4j.appender.stdout.layout.ConversionPattern=%d [%-5p] %c - %m%n

④ 创建 MyBatis 的主要配置文件 mybatis-config.xml，其中包括数据库连接信息，类型别名等等，然后将其加 到 classpath 中；

<?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>

        <typeAlias alias="Student" type="com.mybatis3.domain.Student" />

    </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/mybatis1" />

                <property name="username" value="root" />

                <property name="password" value="" />

            </dataSource>

        </environment>

    </environments>

    <mappers>

        <mapper resource="com/mybatis3/mappers/StudentMapper.xml" />

    </mappers>

</configuration>

⑤创建 SQL 映射器 XML 配置文件 StudentMapper.xml 并且将它放在 com.mybatis3.mappers 包中，注意这个包要在resource下面，如果在main下面的话，会遇到读取不到这个配置文件的问题

 <?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.mybatis3.mappers.StudentMapper">

     <resultMap type="Student" id="StudentResult">

         <id property="studId" column="stud_id" />

         <result property="name" column="name" />

         <result property="email" column="email" />

         <result property="dob" column="dob" />

     </resultMap>

     <select id="findAllStudents" resultMap="StudentResult">

         SELECT * FROM STUDENTS

     </select>

     <select id="findStudentById" parameterType="int" resultType="Student">

         SELECT STUD_ID AS STUDID, NAME, EMAIL, DOB

         FROM STUDENTS WHERE STUD_ID=#{Id}

     </select>

     <insert id="insertStudent" parameterType="Student">

         INSERT INTO STUDENTS(STUD_ID,NAME,EMAIL,DOB)

         VALUES(#{studId },#{name},#{email},#{dob})

     </insert>

 </mapper>

⑥ 新建 MyBatisSqlSessionFactory 单例类

 package com.mybatis3.util;

 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 java.io.*;

 import java.io.IOException;

 import java.io.InputStream;

 /**

  * Created by peng on 2016/8/4.

  */

 public class MyBatisSqlSessionFactory {

     private static SqlSessionFactory sqlSessionFactory;

     public static SqlSessionFactory getSqlSessionFactory(){

         if(sqlSessionFactory==null){

             InputStream inputStream;

             try {

                 inputStream = Resources.getResourceAsStream("mybatis-config.xml");

                 sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

             }

             catch(IOException e){

                 System.out.println("aaa");

                 System.out.println(e.getMessage());

                 throw new RuntimeException(e.getCause());

             }

         }

         return sqlSessionFactory;

     }

     public static SqlSession openSession(){

         return getSqlSessionFactory().openSession();

     }

 }

上述的代码段中，我们创建了一个 SqlSessionFactory 对象，我们将使用它来获得 SqlSession 对象和执行映射的SQL 语句。

⑦ 新建 StudentMapper 接口和 StudentService 类

1. 首先, 创建 JavaBean Student.java

 package com.mybatis3.domain;

 import java.util.Date;

 /**

  * Created by peng on 2016/8/4.

  */

 public class Student {

     private Integer studId;

     private String name;

     private String email;

     private Date dob;

     public String getName() {

         return name;

     }

     public Integer getStudId() {

         return studId;

     }

     public String getEmail() {

         return email;

     }

     public Date getDob() {

         return dob;

     }

     public void setStudId(Integer studId) {

         this.studId = studId;

     }

     public void setName(String name) {

         this.name = name;

     }

     public void setEmail(String email) {

         this.email = email;

     }

     public void setDob(Date dob) {

         this.dob = dob;

     }

 }

2. 创建映射器 Mapper 接口 StudentMapper.java 其方法签名和 StudentMapper.xml 中定义的 SQL 映射定义名 相同

 package com.mybatis3.mappers;

 import com.mybatis3.domain.Student;

 import java.util.List;

 /**

  * Created by peng on 2016/8/4.

  */

 public interface StudentMapper {

 List<Student>findAllStudents();

     Student findStudentById(Integer id);

     void insertStudent(Student student);

 }

3. 现在创建 StudentService.java 实现对表 STUDENTS 的数据库操

 package com.mybatis3.services;

 import com.mybatis3.domain.Student;

 import com.mybatis3.mappers.StudentMapper;

 import com.mybatis3.util.MyBatisSqlSessionFactory;

 import org.apache.ibatis.session.SqlSession;

 import org.slf4j.LoggerFactory;

 import java.util.List;

 /**

  * Created by peng on 2016/8/4.

  */

 public class StudentService {

     private org.slf4j.Logger logger= LoggerFactory.getLogger(getClass());

     public List<Student>findAllStudents()

     {

         SqlSession sqlSession= MyBatisSqlSessionFactory.openSession();

        try {

            StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);

            return studentMapper.findAllStudents();

        }

        finally {

            sqlSession.close();

        }

     }

     public Student findStudentById(Integer studId)

     {

         logger.debug("Select Student By ID:{}",studId);

         SqlSession sqlSession=MyBatisSqlSessionFactory.openSession();

         try{

             StudentMapper studentMapper=sqlSession.getMapper(StudentMapper.class);

             return studentMapper.findStudentById(studId);

         }

         finally {

             sqlSession.close();

         }

     }

     public void createStudent(Student student)

     {

         SqlSession sqlSession=MyBatisSqlSessionFactory.openSession();

         try{

             StudentMapper studentMapper=sqlSession.getMapper(StudentMapper.class);

             studentMapper.insertStudent(student);

             sqlSession.commit();

         }

         finally {

             sqlSession.close();

         }

     }

 }

⑨ 新建一个 JUnit 测试类来测试 StudentService

 package com.mybatis3.services;

 import com.mybatis3.domain.Student;

 import org.junit.AfterClass;

 import org.junit.Assert;

 import org.junit.BeforeClass;

 import org.junit.Test;

 import java.util.Date;

 import java.util.List;

 /**

  * Created by peng on 2016/8/4.

  */

 public class StudentServiceTest {

     private static StudentService studentService;

     @BeforeClass

     public static void setup(){

         studentService=new StudentService();

     }

     @AfterClass

     public static void teardown(){

         studentService=null;

     }

     @Test

     public void testFindAllStudents()

     {

         List<Student>students=studentService.findAllStudents();

         Assert.assertNotNull(students);

         for(Student student:students)

         {

             System.out.println(student);

         }

     }

     @Test

     public void testFindStudentById()

     {

         Student student=studentService.findStudentById(1);

         Assert.assertNotNull(student);

         System.out.println(student);

     }

     @Test

     public void testCCeateStudent()

     {

         Student  student=new Student();

         int id=3;

         student.setStudId(id);

         student.setName("student_"+id);

         student.setEmail("student_"+id+"gmail.com");

         student.setDob(new Date());

         studentService.createStudent(student);

         Student newStudent=studentService.findStudentById(id);

         Assert.assertNotNull(newStudent);

     }

 }

⑩ 它是怎么工作的
首先，我们配置了 MyBatis 最主要的配置文件-mybatis-config.xml,里面包含了 JDBC 连接参数；配置了映射器 Mapper XML 配置文件文件，里面包含了 SQL 语句的映射。  
我们使用 mybatis-config.xml 内的信息创建了 SqlSessionFactory 对象。每个数据库环境应该就一个 SqlSessionFactory 对象实例，所以我们使用了单例模式只创建一个 SqlSessionFactory 实例。  
我们创建了一个映射器 Mapper 接口-StudentMapper，其定义的方法签名和在 StudentMapper.xml 中定义的完全 一样（即映射器 Mapper 接口中的方法名跟 StudentMapper.xml 中的 id 的值相同）。注意 StudentMapper.xml 中 namespace 的值被设置成 com.mybatis3.mappers.StudentMapper，是 StudentMapper 接口的完全限定名。这使我们 可以使用接口来调用映射的 SQL 语句。  
在 StudentService.java 中，我们在每一个方法中创建了一个新的 SqlSession，并在方法功能完成后关闭 SqlSession。每一个线程应该有它自己的 SqlSession 实例。SqlSession 对象实例不是线程安全的，并且不被共享。所 以 SqlSession 的作用域最好就是其所在方法的作用域。从 Web 应用程序角度上看，SqlSession 应该存在于 request 级 别作用域上。

注意：

在看书学习的时候，遇到了几个概念性的问题：

classpath概念：设置Classpath的目的，在于告诉Java执行环境，在哪些目录下可以找到您所要执行的Java程序所需要的类或者包。Java执行环境本身就是一个平台，执行于这个平台上的程序是已编译完成的Java程序(后面会介绍到Java程序编译完成之后，会以.class文件存在)。如果将Java执行环境比喻为操作系统，如果设置Path变量是为了让操作系统找到指定的工具程序(以Windows来说就是找到.exe文件)，则设置Classpath的目的就是让Java执行环境找到指定的Java程序(也就是.class文件)。

本书中有时候提到新建了某文件加入到classpath中，放到webapp下面的WEB-INF下面即可。

resource想新建package却新建不了？

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MBsnY+kzLLtHYAEB1wAAhJtc8BjI+PX7p0KUjDpjkAW9pf/qjnBdQ0AFkAgGjTIgfwyXLuW4lEIpF6edn+q5cfSSQSySfe7/zbPUI2tckBzM3NVSqVgA3b4QCcGwLymaS0Ato6AgBEh4AOwIzoJvdk3l7Wf/VIzq1+RBzAJ4fENKnHho3qVcsdwIkTJ65du1ZXw5AOQH4I0H0VQI3wttUBu13IZ5LkAAAiSRAHYMY/dwewsFJ9+yfJ4NGxtxzAJ8v5J+6x0qO9MmwUTi10ABMTE4VCIUTDkJ8GdHEA+oa/TMo33W8VJVMpcgAAkaSmA5Cz/28dkiX5Jx7JvL0sAn/i7p/knWkAWw7gk/czd4t3k0dyqgNQUwt3/yS/4BFxjeb3ZN5W5uLSl/g0fPkRa+TWRZZd+819S+tCvWzqZePiOICIq2e+E7AJ3wcAALGntgM4lJLh0CbpABYcaQDVAdhXEGQId5R/65CzMPXysgzeybtlsfrY/Wqpl5e1wcvHfv1ql7WWMD7BAcRD3egAAABaRE0HIMK8mEaLxzJqqtVEkJZGQXMAYlatTb6VSfwjOWdzIZktMFMIihswwrYx77cNxmooZ/bLSqFbv9rAHPEeBxAT4QAAIEYEdADKRN/dASwYcddM+ysOQL2CGkrVqxk8ktOT+boD0DyE0ZHM87s3NArNNP491uKFo1/LKyw4NivgAGIiHAAAxIjaqwDKnFuUqIvrzprasrriAIw5tzLVVp2BlLqaYM8B+DoA14YLMofxk8zdeibD1i8OAC3gAAAgVgT5LICIsjbMoKuFUpkG0FYB5DZA+wTdZeXeMUGvywHYGy5IX3JP0pGf0PrFAaAFHAAAxIqg3wdg+0DgPdpnAWzVlGV1M+haG+xzaijVzYG+bfCezBP15ABcGy6onxFQP6rg1S8OIN7CAQBAjGjudwJ+oiy3d/zdHKF6hQMAgBjR9G8F9vn0IEJdLhwAAMQITgZCSAoHAAAxAgeAkFQ3OgDnd/8tzL3e6UEBQBQ4efJkqVxFCJXKPeIAMAEA0BRwAAhJ9YwD4FwAAGgcHABCUq1yAEeOHMm6MTExUbMtDgAAWgQOACGpVjmAxcVFVwewuLhYs22Q6I4DAIAQ4AAQkmrhKsCxY8ds4f/YsWNBGoZ2APmM/JrMVM4sSOVyqUQikczkq9VqNSe/6MsoAIA4gQNASKqFDmBlZWVsbEyG/7GxsZWVlSANQzoAEe4dRQmrMJci8APEGxwAQlKt3Qk4MzMjHcC7774bsFXYHICY36shXjcFuRTxHyDm4AAQkmqtAyiXy4cPHxYJgHK5HLBVY/sAxLxfhHocAABo4AAQkmr5pwHff//9bDb74YcfBm8SehUgkzMfGYHftjCQS1lLArkMZgAgfuAAEJJqx/cBTE5O1lU/9KcBrW1+Rpx3bA2w9gradgwAQCzAASAkxTcCAUCMiKQDWFr44N4H9t72wFR21f6r7NDe2x4YH1zo/CBRF6obHQAAQIsI4gBEQP3apn1f27SvU+FzafXyZnMMQveOLvkPGAeA6hUOAABiRE0HoIZ/HACKtnAAABAjajuAmamvbdp329Bl8ePZ0SkRPtWQLGOtEXqHLpfK1aXVpcG0EYZleXbILFGbG/WtEmd0F791Bm+/Yeg/io5UB+Ds0WWcM1PSc2ye6XyIQi0VDgAAYkRQB6CHXueM3BbpS64OID0uAvOh61rz24YuOy9oC7euDqDGMBxWQ01juPZoH6ee/8ABRF44AACIEbUdwOrSYNoeBQ1bkP7g7Gq1VK5mh/aKaXQNByAn33pewVYiKtvSAO4B238YyiRe1FFthGuPruP0WW5AERMOAABiRMDPAojgKkPv2dFxNTTKH2uuAqj11Sm1KNFm6oo/KHk4gBrDeGAqu6rVMYc0Prjg3qNtnNoSg+kzUISFAwCAGBFkFUCGajkntk3ihT9QsujqhNvTAagx3hbLXYbhugrgPwzFAahbDVQHYM806ONUe3GaEhQ94QAAIEYE3AdgT797LcAH2B9QckzonfsAnNv4w+8D0NfyvfYBuI9Tv3ccQOSFAwCAGFHvpwGtfIDbJvySEjU3z3iuAtguqy7G1+UAvIZh/yyAOaR7Ry/LVQDXHn0cAKsAcVDUHIDzewMX5l7v9KAAoFuI5HcCIhRO0XcALTQB+UyS0wYBegocAEJSsXAArTpTAAcA0GvgABCS6kYHcOTIkawbExMTNdtyqhAA+IADQEiqGx3A4uKiqwNYXFys2TZIdMcBAMQWHABCUt3oAKrV6rFjx2zh/9ixY0EahnUAuVQimcllkolEIpFI5arVXCqRSCQSSpY/b/zWqGCUiIe5VCKZyTiaAECXgQNASKpLHcDKysrY2JgM/2NjYysrK0EaNuAAzNAtYr+I7FaMz2dSZmDPpYxfaw5AbYIHAOhScAAISXWpA6hWqzMzM9IBvPvuuwFbNZQDyPs/dmQBbDmAvKyFAwDoUnAACEl1rwMol8uHDx8WCYByuRywVascQD6TlOl9GfhxAAC9Rm85gKWFD+51fClQUyojVOpmB1CtVt9///1sNvvhhx8Gb9IqB6CU5TNJcgAAPUp7HMDS6uXNzQjGPkHd2QUOAPkrnU4/98KLL+3dv2v3S6++dqjU5Q6gWq1OTk7WVT/spwFrrgJYKwDJVIocAECP0rYcwNnR8VYfs9uGLlCUlE6nR177tXj8zM5nT8+f73YHUC98HwAA+NA2B7C08MG9Lf5q/TZ0gaKkdDp9dPId8fiVX44cn5qJmgMAAPAhtAMQp+sqpwIuDab3bp65vFk/Hdg8kmfJrGA0N5L2M8bZPJtn1PN7jHm8enKPaLi08MG91iGE44OjWhN7F2Zl56VETdnR2dFxY8yOHlGElU6nX9q7v1Sufnm98uOfDn7w8e9xAAAQI8I5ADW4GiWr1kmAJfPIPltOfmlmynZAsBF3Z6b0EwJNSzFkTOiXZqaUs/usY4iVJuZxf2oX/peamTKdiuEbXKt1PEqh1imdTr/4iz2v7D/ws+demHjzeKn79wEAADSRkA7AcVavff5txldHK9UimGHb43HJmWmw5QAWZNdqc3Xeb0VxR9LCuIJ/tY5HKdQ6pdPp41MzagkOIMpUzpy5uWVLp0cB0EU0sg/AnPePDy4EcgClcjU7tNfM2NdwACIhb1SWgb+WA9C60FrZC2VNuX/QqxqKqlQHcGD0V+l0GgcQTSpHjtzYtOnm+vU316/v9FgAuojQqwCDYmFeTaHbl/mNH5dWLw+qS/vWLgFfB6B4iLOj4wFzAFoXsrLbpcyaU5vTygqCWzUUB315vfLsz5/HAUQNNfbjAABshM4BZIeMHXPGYrzuAErK5js1lMpoXdsBrC4Nps2NhENTwXMAVhfqPgDHpeSYla0J7tVQTPTZ8nUcQES4tby8tnv3jY0b1diPAwCw0f7vBDw7Oi6Dbku7aFYm/9SpU/wbyX+dwgH0PD6xX+pGf//NLVtuPv302u7da6OjlTNnKmfO3Fpe7vTYAdpN+x2AulmvpV28YH7Gr803iHpXOIAe5tbVqzeffton8AfRjU2bbm7ZcnPLlrXdu9d2765MTVXOnLl19Wqnbw6gJfTWuQABZXy8kDQ+qlM4AIutB9+z6c35K50elDtNif2BJMxBJqMmDzp99wDhiaQDQCiccAAWTgcQyATkM8lE+w4CEB/wa0fsr5k8ECsLjz9uJA/EygLJA+hucAAISUXQARw9erRUKoVo6OoAXKU1i6sD8DMHGzdqKwtHjlTOnLl18WKbniMAb3AACElF0AFks9lsNjs9PV0ul+tqGNIBdIKu8gE3/uEfbn7nO0Jrzzyz9otfCFVOn5bq9BMGYIADQEgqsg4gm82OjY3Nz88HbxgkuneJAxC0yAfc2LRJRvSbTz9tRfQjR2RE53ME0KPgABCSirIDEExMTCwuLgZpGNIB5DPJRCpnPTZI5aq2FQLrB3u1hgjkA2REf+wxGdHXDh60IjopeogHveUA1EOAEGq6ou8ABOfPn6/ZsGEHkM+kzGifSxnBPZcyLYCs51atYbx8QDOuDRAd2uMAbOf9hL+OtwNoVhcoPkqn08+98OJLe/fv2v3Sq68dKsXBAYyPj1+6dClIwybkAFym96YFqFGtOTh9QPOuDRAF2pYDkAfw9HQXKEpKp9Mjr/1aPH5m57On589H3AHMzc1VKpWADRt1APlMMuGY8JsWIJ9JKr9yqdZEVB/Q7GsD9DZtcwDywJ6e7gJFSel0+ujkO+LxK78cOT41E1kHcOLEiWvXrtXVsFEHYCX8RZRXNgckUynTAHhWazYcDQzgJLQDODs6bpwMpJy+s3nm8uYH9t5mnf5nHrQzuuR2eOD44IxxetDmGeOL/ERlo455tpCoUCo7TgYa1Zo4uqgxJNcbMce2116onDJgO3PIv4uAnaL2K51Ov7R3f6lc/fJ65cc/Hfzg499H0AFMTEwUCoUQDRv4PgBzH4CZ2k+mUsrk3hbovaoBQMsJfTqw7dAd45w9PYjacvJLM1PKQXxK1BRf4ivOGFSD65AxoV+amXI7HXiv0kQ54Vc/608fknqc4N7NM643oo3c2bV9kL53HbBT1BGl0+kXf7Hnlf0HfvbcCxNvHi9Fch9AaBp2AADQ7YR0ACIAP2A7k1eZf89MOU/lUc8Eqnk6sGhizzTUOh1Y78I+JHEpqXtHl1xuRB+5a9h25AA87zpgp6gjSqfTx6dm1BIcQKO09ysBAaAhGtkHYM6AxwcXAjmAUrmaHdqr5Mb9HIBYAjAqy4hbywHoXQQakv1GXByAHE8YBxCk047HwnhKdQAHRn+VTqdxAA2QSzV9Mz8AtJTQqwCDYmFeTpFdlvmNH5dWLw+qS/vWermvA1Bi59nR8YA5AL0LzyGVytXskHFBx404VgHE1ZS1Bms8te46YKcdj4Xoy+uVZ3/+PA4AAGJE6BxAdsjcKycW4x3BTO7jUze7WVPqmg5gdWkwbW6gG5oKngNQuvAcktxa6LwRcwz2nYAlZUnCGk+Auw7YKeq4Plu+jgMAgBjR/u8EPDs63uqw14Yumq5Tp07xb5v/dQoHAAAxov0OQN2s17tdoEgKBwAAMaK3zgVAqKXCAQBAjMABICSFAwCAGIEDQEgKBwAAMQIHgJAUDsDC+d1/b85f6fSgAKCZ4AAQksIBWLh+ATAmwI+VlbXvfrfTgwCoAxwAQlIRdABHjx4tlUohGoY8FyCu3JqevnnffRxADL0FDgAhqQg6AHE68PT0dLlcrqshDiAoKytr3/3uzfXrhWThrbNnVVVee62yZ4+lnTvX/uVfpCqZTGXPnltvvFENdZAjQDhwAAhJRdYBZLPZsbGx+fn54A2DRHccgJz6h9Dali2VTObW1FR1ZaXT9wExBQeAkFSUHYBgYmJicXExSMOwDkAcD5xLJRLmIYHGkUFWgahkIE8SsqpZhepZw9bjIF0E7LQB9Kl/HVF/9+5bZ8403j9A4+AAEJKKvgMQnD9/vmbDRhyAHte1EJzK6XHdqqacKpxLGVfwdgA266CfSByw0/DUMfXfuHHt8ccro6PVPGcmQ9eBA0BIKvoOYHx8/NKlS0EaNpYDMH9SJ/bWjFyUKlFbDdnqRfxyAF5tA3faCPl85dlnb37jG+5R/xvfWPvhD2+98QZRH7ocHABCUhF3AHNzc5VKJWDDpjkAz5grpvJmdLY7gGQm34ADCNJpM7g1Pb32wx/e3LhRdQDVq1ebc3WAFoMDQEgqsg7gxIkT165dq6thcxyAldAXPxi5/Yw9qjtWAcQP+UzSLM5nkglXB6B1kcuY0/0AnTaPlZVbb7yx9vjjwgFUfvWrpl4doFXgABCSiqADmJiYKIT6gFnYTwM64qv/rj/3BQOrVLZOplLuOQCtCzVhEKTTZlMoVEZH1/7t31p1fYCmggNASCqCDiA0fB8AQOSJuQNYurD6/J0rP7jzT6dX7b86vX3lB3d+9daFzg8StU04AACIETUdwNLqjbcF0K8AAAnUSURBVIN3rgzc9T9Szw+vdfydulkDxgEgVTgAAIgRIRzAwF3/c/B459+sgw8YB4ACCgcAADEioAOQMfL09hUZU9VYK6Ps0vE/2YyCWk1exwi922+UytWl1bW3vml0IctPbzdL1OZGfZd+HQO2B2+/Yeg/io5UB+Ds0WWcjhtHPSccAADEiLocgAjVIsI5p9oHj1sR1CpxVLNF+pKrA/jmVyIwz13Xmv9g+w3Xft0GrDmAGsNwWA2zzldvXfC7U2ucjhvveDBDIYQDAIAYEWIVwAjbx/9kPb6w+vydK88Pr4lCdV5uVPvm6oKeQqjhAOTkW+lFu6Der/+ADx6vNQxlEi/qqDbC/U7dxtnlOyRQTeEAACBG1OsAZMJ8Yfgr2+YA2wRdhFJRTYZG+WPNVQC1vjqldu3XZ8CieY1h3Pmn0/pQzSF99dYFjzvVx+m88Y4HMxRCOAAAiBF1rQKIWOga2rUm5or4D7bfsE3ixeRbyaKrE25PB6DGeJ9+9QHrqwD+w1DvTtlqoDoAe6ZBH6fzxjsezFAI4QAAIEaE3gnomhtQd8N5Ldt7L7q7OAB7L44LOrfxh98HoK/le+0DcB+n48Y7HsxQCOEAACBG1OsAZDi07ftzOgCZDHfdhF9SoubB456rAKWy3ouyGF+XA/Aahv2zAOaQnh++IVcBXHv0cQCsAvSucAAWb//Ht21amHu904MCgGYS8+8EREgVDsDC6QBaYwJacE4PAAQDB4CQVAQdwNGjR0ulUoiGrg7AVY0NEAcA0DFwAAhJRdABiNOBp6eny+VyXQ1xAACRBweAkFRkHUA2mx0bG5ufnw/eMEh0xwEA9DQ4AISkouwABBMTE4uLi0EahnMAuVQimcmbD83QbpXmUgkDs5pwAFa55QbymaS90Kuy90UAwBscAEJS0XcAgvPnz9dsGM4BWDP6XCqZTIowbxoAxR5YFUWcN0O2ZRvymZRZVy30quxeDgB+4AAQkoq+AxgfH7906VKQhiFXAczInkslM/lcKpnJV/OZpGkAdJKZvGMVQPvRkQXwqux3EQDwAgeAkFTEHcDc3FylUgnYMOw+ABHvldify9hSAY76bsE7n0nKlQKrCg4AoJngABCSiqwDOHHixLVr1+pqGHonYD6TTCatyCzXAmzZ+VxKSeCr6/niB8UuKDU8KnuWA4AfOACEpCLoACYmJgqFQoiG4T8NqEbgfCapTvy9NvelnHv4rKrJVErLAXhUdisHAD9wAAhJRdABhKZd3wdQF17pfdL+AGHAASAkhQPocnAAAM0EB4CQFA6gy8EBADQTHABCUjgAAIgROACEpHAAABAjcAAISeEAACBGhHMASxdWn7/zq7cudP4tG6EmCgcAADECB4CQFA4AAGJE46sAp06d4l/+jca/OAAAiBHsA0BICgcAADECB4CQVDc6gN9t/WebPn/zPzs9KACIAjgAhKR6wwFgAgCgKeAAEJJqoQM4evRoqVQK0dDVAbiqWUMFgJiAA0BIqoUOQJzSOz09XS6X62oY1gG09Ity+RZegCiAA0BIquUOIJvNjo2Nzc/PB28YZH6PAwCAEOAAEJJqhwMQTExMLC4uBmkYygHkUgmTZCZfFSHbwIzcIornUrKO1SqZyaTMQu1qyUze5eIA0JvgABCSap8DEJw/f75mw2bkAPKZlBmqcynTAwhTIGfy1i+MX1m2QMZ5eU1yAABRAAeAkFT7HMD4+PilS5eCNGzWKoAjC6BXUAO9+qMy4Vem/TgAgCiAA0BIqk0OYG5urlKpBGzYBAegTumt4sAOwCXVjwMAiAI4AISkWu4ATpw4ce3atboaNsEBKFE8n0m65wD8VgHUpQLXtgDQk+AAEJJqoQOYmJgoFAohGob+PgAj7Z/MXFRWAJKplHsOoKquE+g7AV12EVoXZycgQO+CA0BIqme+E7Dl3wjknvwHgEiBA0BIqhsdQLvIZ5La5wIwAACRBweAkFScHYCW7Sf8A8QBHABCUvF2AAAQM1rqAJYuZEbvSuy6KzW/GrTJ/PbErruSMxeaX7neETZ+cdRzwgEAQIyo6QCWVnO5uxLDX7eUmwz6ftoRB+Ac8OhwPsQIcQAxFA4AAGIEDgAHgKRwAAAQIwI6AFuMnN+eGP56Ytf2XKlcXZpMDX89sevBzB9Wtei7a3tOja/GY9FkNT/zoHVN8SvRRI276tVkFPeq7BiwnzOwdR1iJPJ25rebNziZCmGSUFcJBwAAMaLeHIAIikqUtfyBvWYwB+Ccsqtd2HIPXpWdA7aVuzVURhViJKLhg0nR/JxpHXAAPS0cAADEiHAOoFR2mfIayYDtOattEAfgSCEYcVe5mmg7Opz3quwzYCNgKw1LZg5jdDivjbCukRgNtWfDZ7kB9YRwAAAQI8KtApTMKK6G1T8MJ23T3yAOQLQyUutGeXLmglGuzci357wqOwdscwBqQzlUmwOoayTq7dg6lU8I6jnhAAAgRoR3AEoOQERNESlr5AC0GbYVd01nYM28bTFbyKuy24D1VQA9PyFyAFYyv/6R2ByA7TmxlaNeEQ4AAGJEiM8CjA7nlRAeeB+A70p8zdV3/8rOAYfZB1D/SKwcgOKHcAC9KxwAAMSIEA7g4K5jIv+vTf3F5F4JojYHUFLCZG5S/yyAWT46nFMT+9rValW2DTjkZwECj8THAbAK0LvCAQBAjOBbgRGSwgEAQIzAASAkhQMAgBiBA0BICgcAADECB4CQFA4AAGIEDgAhKRwAAMQIHABCUjgAAIgROACEpHAAABAjcAAISeEAACBG4AAQksIBAECMwAEgJIUDAIAYEc4BiKPz1GMAm6iWXhwhH+EAACBG4AAQksIBAECMCOcArCN2HAcCichtRvFcTj8R2Dhwbzglj89RD+yRpw7Ki3c8JKBYCQcAADGi8RzA0mp+ZrsZzidT5lnA+ul/q7ncXZo5UGyBef6eeU1yAKhTwgEAQIxo1iqAOCPYOjxXr7A0mVLPzJU/qofqKmkAHADqjHAAABAjmpADuJAZvSsxOpw3H9fnANRy58URaqdwAAAQI5rgAJQo/ofhpHsOwG8VwKo2v92lLUJtEw4AAGJE6O8DEGn/XQ9mLl/Pzzxo5vC3p1xzAKWytVvQvhPQsYtQvXjHQwKKlXAAABAjOvKNQK7Jfy+dOnWKf/m3Pf/iAAAgRrTHASyt5mce1D4XIPYNINRVwgEAQIxoWw5AzfYT/lF3CgcAADGCcwEQksIBAECMwAEgJIUDAIAYgQNASAoHAAAxAgeAkBQOAABiBA4AISkcAADECBwAQlI4AACIETgAhKRwAAAQI3AACEnhAAAgRuAAEJLCAQBAjMABICSFAwCAGIEDQEjqfwGWBHGy4RsAugAAAABJRU5ErkJggg==" alt="" />

这两个文件夹的类型都是Sources的时候才能新建package，由于博主学习maven有限，原理不太明白，有懂的读者欢迎指明。

最后运行了测试类，运行成功。