如何搭建第一个mybatis项目

思路

搭建环境——>导入Mybatis——>编写代码——>测试！

搭建环境

搭建一个数据库并新建一个表

create database mybatis;
use mybatis;
create table user{
id int(10) not null primary key comment '编号',
name varchar(30) comment '名字',
pwd varchar(30) comment '密码'
} comment '学生';
insert into mybatis.user(id,namr,pwd) values
(1,'java',1223456),
(2,'dewie',31251263),
(3,'cnwuiv',243678623);

新建一个maven项目

导入maven依赖

mysql
mysql-connector-java
8.0.33



org.mybatis
mybatis
3.5.13



junit
junit
4.13.2
test

 在resource文件夹中编写mybatis的核心文件mybatis-config.xml

为了提高代码的复用性，将mybatis开启事务的代码封装成工具类

新建一个工具包util 在在里面创建MybatisUtil

package com.lyc.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 MyabtisUtil {
    private static SqlSessionFactory sqlSessionFactory;
    static {
        String dataSource = "mybatis-config.xml";
        try {
            InputStream stream = Resources.getResourceAsStream(dataSource);
          sqlSessionFactory =  new SqlSessionFactoryBuilder().build(stream);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession(true);//自动提交事务
    }
}

根据表中数据来编写实体类，新建一个pojo包，创建User类

package com.lyc.pojo;

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

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

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getPwd() {
        return pwd;
    }

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

在创建包mapper,新建接口UserMapper和UserMapper.xml

并在接口里写入CRUD方法，在UserMapper.xml中写入对应的SQL语句

注：每一个Mapper.xml文件都需要在Mybatis核心配置文件中注册！

UserMapper.java

package com.lyc.mapper;

import com.lyc.pojo.User;

public interface UserMapper {
    User getUserById(int id);
}

UserMapper.xml

    
       select * from mybatis.user where id =#{id}
    

测试

public class MyTest {
    @Test
    public void test()
    {
        SqlSession sqlSession = MyabtisUtil.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.getUserById(1);
        sqlSession.close();
    }
}

可能会遇到的问题：

1.配置文件没有注册

2.绑定接口错误

3.方法名不对

4.返回类型不对

5.Maven导出资源问题