第一个mybatis项目

一、数据库环境搭建

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CREATE DATABASE `mybatis`;
use `mybatis`;
create TABLE `saxon`(
`id` INT(10) not null ,
`user` VARCHAR(20) not null,
`pwd` VARCHAR(10) not null DEFAULT "saxon",
PRIMARY KEY(`id`)
)ENGINE=INNODB,CHARSET=utf8;


use `mybatis`;
INSERT INTO  `saxon`(`id`,`user`,`pwd`) VALUES(1,'saxon','1234567')

二、建立一个项目

1.配置文件：

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<?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/smbms?useUnicode=true&amp;characterEncoding=utf8&amp;useSSL=true"/>
                <property name="username" value="root"/>
                <property name="password" value="1234567"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="org/mybatis/example/BlogMapper.xml"/><!-- 目录下的xml文件，中间用/隔开-->
    </mappers>
</configuration>

三、编写工具类

UserMapping:

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<?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.saxon.Dao.UserDao">
    <select id="getUserList" resultType="com.saxon.pojo.User">
    select * from mybatis.saxon
  </select>
</mapper>

工具类：

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package com.saxon.Util;

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 MybatisUnit {
    private  static SqlSessionFactory sqlSessionFactory;//获得工厂，产生sqlsession；

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



    //获得SQL session对象，就是jdbc中的statement对象，操作数据库
    public  static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession ();
    }
}

四、编写一个实体类

pojo:

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package com.saxon.pojo;

public class User {
    private int id;
    private String user;
    private String pwd;

    public User () {
    }

    public User (int id, String user, String pwd) {
        this.id = id;
        this.user = user;
        this.pwd = pwd;
    }

    public int getId () {
        return id;
    }

    public void setId (int id) {
        this.id = id;
    }

    public String getUser () {
        return user;
    }

    public void setUser (String user) {
        this.user = user;
    }

    public String getPwd () {
        return pwd;
    }

    public void setPwd (String pwd) {
        this.pwd = pwd;
    }
}

五、测试

测试代码;

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package com.saxon.Dao;

import com.saxon.Util.MybatisUnit;
import com.saxon.pojo.User;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {
    @Test
    public void test () {
        //获得sqlsession对象
        SqlSession sqlSession = MybatisUnit.getSqlSession ();
        //获得mapper对象,为了得到userdao，使用里面的方法；
        UserDao mapper = sqlSession.getMapper (UserDao.class);
        List<User> userList = mapper.getUserList ();
        for (User user : userList) {
            System.out.println (user);
        }
        //关闭sqlsession
        sqlSession.close ();
    }
}

==特别要注意的是，不要在配置文件，关键的xml里面写中文注释，会出现 2 字节的 UTF-8 序列的字节 2 无效的错误,，原因在编码，不清楚就不弄了==