MyBatis基础工程

一个MyBatis基础工程

1. 搭建数据库

    CREATE DATABASE `mybatis`;
    USE `mybatis`;
    DROP TABLE IF EXISTS `user`;
    CREATE TABLE `user` (
    `id` int(20) NOT NULL,
    `name` varchar(30) DEFAULT NULL,
    `pwd` varchar(30) DEFAULT NULL,
    PRIMARY KEY (`id`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
    insert into `user`(`id`,`name`,`pwd`) values (1,'hello','123456'),(2,'张
    三','abcdef'),(3,'李四','987654');

2. . 编写MyBatis配置文件（如：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>
    <!--在资源目录创建db.properties文件，记录数据库信息-->
    
    <properties resource="db.properties"/>
    
	<!--默认使用id为development的环境-->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
        
        <!--或者使用test环境配置，不创建独立的db.properties文件-->
        <environment id="test">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>

    </environments>
    <mappers>
        <mapper resource="com/lf/dao/UserMapper.xml"/>
    </mappers>

</configuration>

3. 编写MyBatis工具类（如：MybatisUtils.java）

package com.lf.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 {
    //提升作用域
    private static SqlSessionFactory sqlSessionFactory;

    static{
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
    //获取SqlSession连接
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}

4. 创建实体类（如：User.java）

public class User {
    private int id; //id
    private String name; //姓名
    private String pwd; //密码
    //构造,有参,无参
    //set/get
    //toString()
}

5. 编写实体类对应的Mapper接口（如：UserMapper）

package com.lf.dao;

import com.lf.pojo.User;
import java.util.List;

public interface UserMapper {

    //查询全部用户
    List<User> getUserList();

    //根据字段查询用户
    List<User> getUserLike(String value);

    //根据ID查询用户
    User getUserById(int id);

    //insert一个用户
    int addUser(User user);

    //修改用户
    int updateUser(User user);

    //删除一个用户
    int deleteUser(int id);
}

6. 编写实体类对应的Mapper.xml配置文件（如：UserMapper.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">

<mapper namespace="com.lf.dao.UserMapper">

    <select id="getUserLike" resultType="com.lf.pojo.User">
        select * from mybatis.user where name like "%"#{value}"%"
    </select>

    <select id="getUserList" resultType="com.lf.pojo.User">
       select * from mybatis.user
   </select>

    <insert id="addUser" parameterType="com.lf.pojo.User">
        insert into mybatis.user (id,name,pwd) values (#{id},#{name },#{pwd});
    </insert>

    <update id="updateUser" parameterType="com.lf.pojo.User">
        update user set name=#{name},pwd=#{pwd} where id=#{id};
    </update>

</mapper>

7. 编写测试类 （可在test文件夹中测试）

package com.lf.dao;

import com.lf.pojo.User;
import com.lf.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;

public class UserDaoTest {
    //查询所有姓蓝的用户
    @Test
    public void getUserLike(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        
        List<User> userList = mapper.getUserLike("蓝%");

        for (User user : userList) {
            System.out.println(user);
        }
        
        sqlSession.close();
    }

    //查询所有数据
    @Test
    public void test() {
        //第一步：获得SqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        try {
            UserMapper userDao = sqlSession.getMapper(UserMapper.class);
            List<User> userList = userDao.getUserList();
            for (User user : userList) {
                System.out.println(user);
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //关闭SqlSession
            sqlSession.close();
        }
    }
}