MyBatis的基本使用

MyBatis的基本使用情况的一次记录

添加依赖

Maven 中添加如下依赖

<dependencies>
    <!-- MyBatis -->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.7</version>
    </dependency>

    <!-- PostgreSQL数据库驱动 -->
    <dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
        <version>42.2.24</version>
    </dependency>
</dependencies>

创建数据库和表

-- 创建数据库
CREATE DATABASE emp_database;

-- 创建数据表
CREATE TABLE employee
(
    employee_id int,    -- 雇员id
    name        text,   -- 姓名
    salary      numeric -- 薪水
);

创建 employee 表对应的 POJO 类

package cn.zzq.model;

public class Employee {
    private int employeeId;
    private String name;
    private float salary;


    public Employee(int employeeId, String name, float salary) {
        this.employeeId = employeeId;
        this.name = name;
        this.salary = salary;
    }

    public int getEmployeeId() {
        return employeeId;
    }

    public void setEmployeeId(int employeeId) {
        this.employeeId = employeeId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public float getSalary() {
        return salary;
    }

    public void setSalary(float salary) {
        this.salary = salary;
    }
}

XML 配置

添加 MyBatis 的 XML 配置文件如下：

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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!-- 数据库驱动，这里使用的是pg，故导入pg的驱动类名-->
                <property name="driver" value="org.postgresql.Driver"/>

                <!-- 数据库连接的url-->
                <property name="url" value="jdbc:postgresql://localhost:5432/emp_database"/>

                <!-- 数据库用户名与密码-->
                <property name="username" value="postgres"/>
                <property name="password" value="postgres"/>
            </dataSource>
        </environment>
    </environments>

    <!-- mapper映射文件-->
    <mappers>
        <mapper resource="mapper/employee.xml"/>
    </mappers>
</configuration>

mapper 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:根标签，namespace：命名空间，随便写，一般保证命名空间唯一 -->
<mapper namespace="Employee">

    <!-- 创建一个查询语句，用于查找所有的雇员 -->
    <select id="selectAllEmployee" resultType="cn.zzq.model.Employee">
        SELECT *
        FROM employee
    </select>

    <!-- 创建插入语句，#{这里填写POJO中的属性名}-->
    <insert id="insertEmployee" parameterType="cn.zzq.model.Employee">
        INSERT INTO employee(employee_id, name, salary)
        VALUES (#{employeeId}, #{name}, #{salary})
    </insert>
    <!--查询工资大于5000的人员信息-->
    <select id="selectPersonSalaryBiggerThan5000" resultType="cn.zzq.model.Employee">
        SELECT *
            FROM employee
        WHERE salary > 5000
    </select>
</mapper>

编写主函数

package cn.zzq;

import cn.zzq.model.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 java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class Main {
    public static void main(String[] args) throws IOException {
        String mybatisConfigPath = "mybatis-config.xml";
        // 读取配置文件
        InputStream inputStream = Resources.getResourceAsStream(mybatisConfigPath);
        // 构建sqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        // 获取sqlSession
        SqlSession sqlSession = sqlSessionFactory.openSession();

        try {
            // 定义一个employee的entity
            Employee employee = new Employee(1, "EmployTest", 23);
            // 将其插入数据表中
            sqlSession.selectOne("Employee.insertEmployee", employee);
            // 查询数据表
            List<Employee> employeeList = sqlSession.selectList("Employee.selectAllEmployee");
            System.out.println(employeeList);

            sqlSession.selectOne("Employee.insertEmployee", new Employee(5, "Test", 6000));
            sqlSession.selectOne("Employee.insertEmployee", new Employee(7, "test1", 5100));

            List<Employee> persons1 = sqlSession.selectList("Employee.selectPersonSalaryBiggerThan5000");
            System.out.println(persons1);


        } finally {
            sqlSession.close();
        }
    }
}

输出结果

[Employee{employeeId=1, name=‘EmployTest’, salary=23.0}]
[Employee{employeeId=5, name=‘Test’, salary=6000.0}, Employee{employeeId=7, name=‘test1’, salary=5100.0}]

参考文献

MyBatis 官网中文入门指南