mybatis（新建mybatis的maven项目、工具类）

1、新建父工程，删除src目录

2、新建子工程（maven的子模块）

此时的父工程的配置文件为：

<?xml version="1.0" encoding="UTF-8"?>
<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/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <!--父工程-->
    <groupId>pers.zhb.study</groupId>
    <artifactId>mybatis_study</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>test_02</module>
    </modules>
    <!--依赖-->
    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.6</version>
        </dependency>
    </dependencies>
    <!--在bulid中配置resources，防止资源导出失败的问题-->
    <build>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>
</project>

子工程的配置文件：

<?xml version="1.0" encoding="UTF-8"?>

<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/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>mybatis_study</artifactId>
        <groupId>pers.zhb.study</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>test_02</artifactId>
    <packaging>war</packaging>

    <name>test_02 Maven Webapp</name>
    <!-- FIXME change it to the project's website -->
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>RELEASE</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>RELEASE</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>RELEASE</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>

    <build>
        <finalName>test_02</finalName>
        <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
            <plugins>
                <plugin>
                    <artifactId>maven-clean-plugin</artifactId>
                    <version>3.1.0</version>
                </plugin>
                <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
                <plugin>
                    <artifactId>maven-resources-plugin</artifactId>
                    <version>3.0.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.8.0</version>
                </plugin>
                <plugin>
                    <artifactId>maven-surefire-plugin</artifactId>
                    <version>2.22.1</version>
                </plugin>
                <plugin>
                    <artifactId>maven-war-plugin</artifactId>
                    <version>3.2.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-install-plugin</artifactId>
                    <version>2.5.2</version>
                </plugin>
                <plugin>
                    <artifactId>maven-deploy-plugin</artifactId>
                    <version>2.8.2</version>
                </plugin>
            </plugins>
        </pluginManagement>
        <resources>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>

</project>

这就体现出了分模块开发的好处：父模块导入依赖后子模块不需要重新导入，子模块继承父模块的依赖

注意：maven创建工程配置文件不生效问题：https://tech.souyunku.com/zhai1997/p/12770767.html

3、书写pojo

package pers.zhb.pojo;

import java.io.Serializable;

public class Student implements Serializable {
    private static final long serialVersionUID = 1L;
    private String studentno;
    private String sname;
    private String sex;
    private String birthday;
    private String classno;
    private String point;
    private String phone;
    private String email;
    private Clas clas;
    @Override
    public String toString() {
        return "Student{" +
                "studentno='" + studentno + '\'' +
                ", sname='" + sname + '\'' +
                ", sex='" + sex + '\'' +
                ", birthday='" + birthday + '\'' +
                ", classno='" + classno + '\'' +
                ", point='" + point + '\'' +
                ", phone='" + phone + '\'' +
                ", email='" + email + '\'' +
                ", clas=" + clas +
                '}';
    }
    public Clas getClas() {
        return clas;
    }
    public void setClas(Clas clas) {
        this.clas = clas;
    }
    public String getStudentno() {
        return studentno;
    }
    public void setStudentno(String studentno) {
        this.studentno = studentno;
    }
    public String getSname() {
        return sname;
    }
    public void setSname(String sname) {
        this.sname = sname;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
    public String getBirthday() {
        return birthday;
    }
    public void setBirthday(String birthday) {
        this.birthday = birthday;
    }

    public String getClassno() {
        return classno;
    }
    public void setClassno(String classno) {
        this.classno = classno;
    }
    public String getPoint() {
        return point;
    }
    public void setPoint(String point) {
        this.point = point;
    }
    public String getPhone() {
        return phone;
    }
    public void setPhone(String phone) {
        this.phone = phone;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }
}

4、编写mybatis的核心配置文件

<?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="jdbc.properties"/>
    <environments default="development">
        <environment id="development">
            <!-- 使用jdbc事务管理 -->
            <transactionManager type="JDBC" />
            <!-- 数据库连接池 -->
            <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="pers/zhb/dao/StudentMapper.xml"></mapper>
    </mappers>
</configuration>

数据库的参数：

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

注意：子配置文件需要被引入到核心配置文件

5、书写mybatis的工具类

package pers.zhb.utils;

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.IOException;
import java.io.InputStream;

public class MybatisUtils{
    private static SqlSessionFactory sqlSessionFactory;
    static {
        try{
            //加载核心配置文件
            String resource = "sqlMapConfig.xml";
            InputStream in = Resources.getResourceAsStream(resource);
            //创建SqlSessionFactory
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        }catch (IOException e){
            e.printStackTrace();
        }
    }
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

SqlSessionFactoryBuilder：一旦创建了sqlSessionFactory就不再需要SqlSessionFactoryBuilder了

sqlSessionFactory：一旦被创建就会在应用的运行期间一直存在，不会对其它或者创建另一个实例

sqlsession：每一个线程都有自己的sqlSession实例，不是线程安全的不能被共享

6、书写dao层的接口，以及绑定该接口的配置文件

接口：

package pers.zhb.dao;

import pers.zhb.pojo.Student;

import java.util.List;

public interface StudentDao {
    List<Student> getStudentList();
}

以上是为了理解，将报名和类名都写成了dao，在mybatis中一般写为mapper：

public interface StudentMapper {
    List<Student> getStudentList();
}

配置文件：

<?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="pers.zhb.dao.StudentDao"><!--绑定一个dao接口-->
    <select id="getStudentList" resultType="pers.zhb.pojo.Student">
    select * from student
    </select>
</mapper>

在不使用mybatis的时候，在书写dao层的接口后需要创建接口的实现类，通过执行sql语句来实现对数据库的操作。然而，在mybatis中实现类的功能被配置文件代替了。

7、测试

方式一：

package pers.zhb.test;

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import pers.zhb.dao.StudentDao;
import pers.zhb.pojo.Student;
import pers.zhb.utils.MybatisUtils;

import java.util.List;

public class MyTest {
    @Test
    public void test(){
        SqlSession sqlSession= MybatisUtils.getSqlSession();
        StudentDao studentDao=sqlSession.getMapper(StudentDao.class);
        List<Student> students=studentDao.getStudentList();
        for(Student student:students){
            System.out.println(student);
        }
        sqlSession.close();
    }
}

Student{studentno='201814', sname='zhai3', sex='男', birthday='1998-11-11', classno='80501', point='892', phone='19837372534', email='null', clas=null}
Student{studentno='201815', sname='qwerr', sex='男', birthday='1998-11-11', classno='80501', point='892', phone='19837372534', email='null', clas=null}
Student{studentno='201816', sname='jiayou', sex='男', birthday='1998-11-11', classno='80501', point='892', phone='19837372534', email='null', clas=null}
Student{studentno='201817', sname='null', sex='null', birthday='null', classno='2', point='null', phone='null', email='null', clas=null}
Student{studentno='201818', sname='null', sex='null', birthday='null', classno='2', point='null', phone='null', email='null', clas=null}

方式二（不推荐）：

package pers.zhb.test;

import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import pers.zhb.pojo.Student;
import pers.zhb.utils.MybatisUtils;

import java.util.List;

public class MyTest {
    @Test
    public void test(){
        SqlSession sqlSession= MybatisUtils.getSqlSession();
        List<Student> students=sqlSession.selectList("pers.zhb.dao.StudentDao.getStudentList");
        for(Student student:students){
            System.out.println(student);
        }
        sqlSession.close();
    }
}

8、项目结构