员工管理系统(Employee management system)

需求描述

实现思路

需求包括增删改查，可以使用mybatis框架快速满足需求

创建一个maven项目Ems(Employee management system)

修改pom.xml配置

<?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>

  <groupId>org.zdx-1</groupId>
  <artifactId>Ems</artifactId>
  <version>1.0</version>

  <properties>
    <maven.compiler.source>8</maven.compiler.source>
    <maven.compiler.target>8</maven.compiler.target>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.2</version>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.18</version>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
  <build>
    <resources>
      <resource>
        <directory>src/main/java</directory>
        <includes>
          <include>**/*.properties</include>
          <include>**/*.xml</include>
        </includes>
        <filtering>true</filtering>
      </resource>
    </resources>
  </build>
</project>

建立对应的文件目录

使用MySql建立数据库连接

新建数据库Ems，新建表employee，添加几条数据

use ems;
create table employee(
    id int primary key auto_increment,
    name varchar(20),
    age int,
    position varchar(20)
);
insert into employee (name, age, position)
VALUES
    ('John', 20, 'developer'),
    ('Bob', 21, 'developer'),
    ('测试员01', 22, 'developer');

在resources中添加项目连接配置

mybatis-config.xml

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybaties.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <properties resource="db.properties"/>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${mysql.driver}"/>
                <property name="url" value="${mysql.url}"/>
                <property name="username" value="${mysql.username}"/>
                <property name="password" value="${mysql.password}"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="mapper/UserMapper.xml"/>
        <mapper resource="com/example/mapper/StudentMapper.xml"/>
        <mapper resource="com/example/mapper/CustomerMapper.xml"/>
    </mappers>
</configuration>

db.properties

mysql.driver=com.mysql.cj.jdbc.Driver
mysql.url=jdbc:mysql://localhost:3306/Ems?serverTimezone=UTC&characterEncoding=utf8&useUnicode=true&useSSL=false
mysql.username=root
mysql.password=123456

编写一个utils文件MyBatisUtils.java

package com.zdx.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.Reader;

public class MyBatisUtils {
    private static SqlSessionFactory sqlSessionFactory=null;
    static {
        try{
            Reader reader= Resources.getResourceAsReader("mybatis-config.xml");
            sqlSessionFactory=new SqlSessionFactoryBuilder().build(reader);
        }catch (IOException e){
            e.printStackTrace();
        }
    }
    public static SqlSession getSession(){
        return sqlSessionFactory.openSession();
    }
}

这段代码是MyBatisUtils工具类的实现，用于提供SqlSession的获取方法，从而方便地进行数据库操作。具体来说：

1. 这个类首先定义了一个静态的SqlSessionFactory变量sqlSessionFactory，用于存储SqlSessionFactory对象，它是MyBatis的核心对象，可以创建SqlSession实例。
2. 在静态代码块中，通过Resources类的getResourceAsReader方法读取mybatis-config.xml配置文件，并使用SqlSessionFactoryBuilder的build方法构建SqlSessionFactory对象。
3. 定义了一个公共的静态方法getSession，该方法返回一个SqlSession对象。通过调用sqlSessionFactory的openSession方法来创建SqlSession实例，从而可以执行MyBatis的SQL语句。

总结：这段代码的作用是通过MyBatisUtils工具类简化获取SqlSession的过程，使得开发者能够更加方便地进行数据库操作。

在pojo中创建employee实体类

package com.zdx.pojo;
public class employee {
    private int id;
    private String name;
    private int age;
    private String position;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getPosition() {
        return position;
    }
    public void setPosition(String position) {
        this.position = position;
    }
    public employee(int id, String name, int age, String position) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.position = position;
    }
    public employee() {
    }
    //构造方法
    //重写toString方法
}

在Mapper编写对应的查询条件

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

<mapper namespace="com.zdx.mapper.EmployeeMapper">
    <select id="findAll" resultType="com.zdx.pojo.Employee" resultMap="EmployeeMap">
        select * from employee where id=1
    </select>
    <resultMap type="com.zdx.pojo.Employee" id="EmployeeMap">
        <id property="id" column="id"/>
        <result property="name" column="name"/>
        <result property="age" column="age" />
        <result property="position" column="position"/>
    </resultMap>
    <select id="findById" parameterType="int" resultMap="EmployeeMap">
        select * from employee where id=#{id}
    </select>
    <insert id="insert" parameterType="com.zdx.pojo.Employee" >
        insert into employee(name,age,position) values(#{name},#{age},#{position})
    </insert>
    <update id="update" parameterType="com.zdx.pojo.Employee">
        update employee set name=#{name},age=#{age},position=#{position} where id=#{id}
    </update>
</mapper>

在test/java中编写测试类EmployeeTest

import com.zdx.pojo.Employee;
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.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.Reader;

public class EmployeeTest {
    private SqlSessionFactory sqlSessionFactory;
    private SqlSession sqlSession;
    @Before
    public void init(){
        String resources ="mybatis-config.xml";
        Reader reader=null;
        try {
            reader= Resources.getResourceAsReader(resources);
            SqlSessionFactory sqlMapper=new SqlSessionFactoryBuilder().build(reader);
            sqlSession=sqlMapper.openSession();

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    @Test
    public void testSelectAll(){
        Employee employee=sqlSession.selectOne("com.zdx.mapper.EmployeeMapper.findAll");
        System.out.println(employee);
    }
    @Test
    public void testDelete(){
        Employee employee=new Employee(1,"张三",20,"manager");
        sqlSession.delete("com.zdx.mapper.EmployeeMapper.delete",employee);
    }
    @Test
    public void testInsert(){
        Employee employee=new Employee(1,"张三",20,"manager");
        sqlSession.insert("com.zdx.mapper.EmployeeMapper.insert",employee);
    }
    @Test
    public void testUpdate(){
        Employee employee=new Employee(1,"张三",20,"manager");
        sqlSession.update("com.zdx.mapper.EmployeeMapper.update",employee);
        System.out.println(employee.getName().toString());
    }
    @After
    public void destroy(){
        sqlSession.commit();
        sqlSession.close();
    }
}

其余实现基本同上面一致，故不再记录。

代码实现

代码仓库：https://github.com/zdx-1/JavaEE-Learn