mybatis学习3-入门案例，注解方式

与mapper.xml方式配置的不同有：没有了UserMapper.xml文件

mybatis注解方式底层的实现是反射。

1.前期mysql准备

CREATE DATABASE mybatis;

use mybatis;
CREATE TABLE user(
id int PRIMARY KEY auto_increment,
name VARCHAR(30) DEFAULT NULL,
pwd VARCHAR(30) DEFAULT NULL
)ENGINE = INNODB DEFAULT CHAR SET utf8

2.实体类

public class User {
    private int id;
    private String name;
    private String pwd;
    ....
}

3.UserMapper接口

public interface UserMapper {
    @Select("select * from user;")
    List<User> getUserList();
    @Select("select * from user where id = #{id}")
    User getUserById(int id);
    @Insert("insert into user (name,pwd) values(#{name},#{pwd})")
    int addUser(User user);
    @Update("update user set name = #{name},pwd=#{pwd} where id = #{id }")
    int updateUser(User user);
    @Delete(" delete from user where id = #{id}")
    int deleteUser(int id);
}

4.工具类

public class MybatisUtil {
    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            //第一步，获取mqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //    既然有了 SqlSessionFactory，顾名思义，我们就可以从中获得 SqlSession 的实例了。
//    SqlSession 完全包含了面向数据库执行 SQL 命令所需的所有方法。
//    你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句。
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
}

5.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>
    <!--配置别名-->
    <typeAliases>
        <package name="com.cong.pojo"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <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>
    <!--每一个mapper.xml文件都需要在mybatis核心配置文件中注册-->
    <mappers>
        <!--常用的方式，每添加一个mapper文件就注册一个-->
        <!--<mapper resource="com/cong/mapper/UserMapper.xml"></mapper>-->
        <!--下面两个的容易出错，接口和mapper.xml文件必须同名且在同一包下-->
        <mapper class="com.cong.mapper.UserMapper"/>
        <!--<package name="com.cong.mapper"></package>-->
    </mappers>
</configuration>

6.测试类

package com.cong.mapper;

import com.cong.pojo.User;
import com.cong.utils.MybatisUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserMapperTest {
    @Test
    public void getUserList(){
        //1.获得sqlsession对象
        SqlSession sqlSession= MybatisUtil.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List<User> list = userMapper.getUserList();
        for (User user : list) {
            System.out.println(user.toString());
        }
        sqlSession.close();
    }
    @Test
    public void getById(){
        //1.获得sqlsession对象
        SqlSession sqlSession= MybatisUtil.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = userMapper.getUserById(3);
        System.out.println(user.toString());
        sqlSession.close();
    }
    @Test
    public void save(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = new User();
        user.setName("彩虹");
        user.setPwd("182184");
        int res = userMapper.addUser(user);
        if(res>0){
            System.out.println("插入成功");
        }
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user = new User();
        user.setName("红红");
        user.setPwd("182184");
        user.setId(3);
        userMapper.updateUser(user);
        sqlSession.commit();
        sqlSession.close();
    }
    @Test
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        userMapper.deleteUser(9);
        sqlSession.commit();
        sqlSession.close();
    }
}