MyBatis简介及测试

MyBatis简介

MyBatis是一个半自动化的持久层框架。
sql与java编码分开，功能边界清晰，一个专注业务，一个专注数据。

MyBatis的使用

创建测试的数据库mybatis，再创建一个student表

1、导入MyBatis.jar等相应的数据库连接驱动等相应的包

log4j.jar用于打印数据库日志（需要编写相应的.xml配置文件）

2、创建对应于数据库中表的javaBean对象

package bean;

public class Employee {
    private Integer id;
    private String name;
    private String gender;
    private String email;

    public Employee() {
    }

    public Employee(Integer id, String name, String gender, String email) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.email = email;
    }

    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 String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    @Override
    public String toString() {
        return "Employee{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                ", email='" + email + '\'' +
                '}';
    }
}

3、编写全局配置文件

mybatis-config.xml

<?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">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?serverTimezone=Asia/Shanghai"/>
                <property name="username" value="root"/>
                <property name="password" value="2824199842"/>
            </dataSource>
        </environment>
    </environments>

   <!-- 将写好的sql映射文件注册到全局配置文件中-->
    <mappers>
        <mapper resource="EmployeeMapper.xml"/>
    </mappers>
</configuration>

4、编写sql映射文件(采用面向接口的方式)

创建dao层，并添加EmployeeDao接口

package dao;

public interface EmployeeDao {

    public Employee getEmpById(Integer id);
}

EmployeeMapper.xml

<?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">
<!-- namespace  名称空间  1.通过 namespace.id 来确定要执行的sql语句
                         2.指定为接口的全类名，用于绑定接口(一般使用这种方式)
     id  唯一标识   用于唯一标识一条sql语句
     result  返回值类型
     #{id}  从传递过来的参数中取出id值
-->
<mapper namespace="dao.EmployeeDao">
    <!-- 将接口中的函数与sql语句绑定-->
    <select id="getEmpById" resultType="bean.Employee">
        select * from employee where id = #{id}
    </select>
</mapper>

5、测试是否成功

MybaitTest.java

package test;

public class MyBatisTest {

    public SqlSessionFactory getSqlSessionFactory() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        // 根据 xml 配置文件创建一个SqlSessionFactory对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        return sqlSessionFactory;
    }

    @Test
    public void test2() throws IOException {
        SqlSession sqlSession = null;
        try {
            // 1.获取SqlSessionFactory对象
            SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
            // 2.获取sqlSession对象 用于执行sql语句
            sqlSession = sqlSessionFactory.openSession();
            // 3.获取接口实现类对象
            // 会为接口自动创建一个代理对象  代理对象去执行增删改查方法
            EmployeeDao mapper = sqlSession.getMapper(EmployeeDao.class);
            System.out.println(mapper.getClass());// 代理对象
            // 4.使用接口实现类对象调用接口中的方法
            Employee emp = mapper.getEmpById(1);
            System.out.println(emp);
        } finally {
            if(sqlSession!=null){
                sqlSession.close();
            }
        }
    }
}