封装 MyBatis 工具类

注：本文仅提供作者自己查阅使用

导入MyBati、log4j以及 mysql 驱动 相关的jar包

规范：

• MyBatis配置文件一般建议使用 mybatis-config.xml文件

  文件位置
  

  整个结构：

  tips：这里的小鸟是装了一个叫 MyBatisX 的一个插件
  

mybatis-config.xml

log4j日志配置文件，此配置文件在出现错误，或者异常的时候打印日志信息

# Global logging configuration
log4j.rootLogger=ERROR, stdout
# MyBatis logging configuration...
log4j.logger.org.mybatis.example.BlogMapper=TRACE
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

关联外部 .xml文件 一般建议和实体类放在一起

    
        select * from user where id = #{id};
    

    
    
        select * from user;
    
    
    
    
    
        select * from `user` where username like '%${value}%';
    

    
    
    
        insert into user(username,password)values(#{username},#{password});
    

    
    
        update user set username = #{username},password = #{password} where id = #{id};
    

    
    
        delete from user where id = #{id};
    

UserMapper接口

package mapper;

import org.apache.ibatis.annotations.Param;
import pojo.User;

import java.util.List;
import java.util.Map;

public interface UserMapper {
    //根据id来查询数据
    User selectUserById(int id);
    List selectUserList();
    List selectUserLikeUserName(String username);
//    Integer addUser(User user);
    Integer addUser(@Param(value = "username") String name,@Param(value = "password") String pwd);
//    Integer addUser(Map map);
    Integer updateUser(User user);
    Integer deleteUser(int id);
}

User实体类

package pojo;

public class User {
    private Integer id;
    private String username;
    private String password;

    public User() {
    }

    public User(Integer id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public Integer getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + ''' +
                ", password='" + password + ''' +
                '}';
    }
}

实体类对应库中的表

MyBatisUtils

package 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 {
    private static SqlSessionFactory sqlSessionFactory;

    static {
        //MyBatis 核心配置文件名称
        String config = "mybatis-config.xml";
        InputStream is = null;
        try {
            is = Resources.getResourceAsStream(config);
        } catch (IOException e) {
            e.printStackTrace();
        }
        //创建工厂
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
    }

    //获取SqlSession
    public static SqlSession getSqlSession(){
        //openSession() 里面可以不写true，不写则默认为 false 需要手动提交事务，手动提交事务需要调用 commit()方法，否则，处理的数据，不会持久化到数据库中。
        return sqlSessionFactory.openSession(true);//写 true 代表自动管理事务
    }

    //释放资源
    public static void closeSqlSession(SqlSession sqlSession){
        if (sqlSession != null){
            sqlSession.close();
        }
    }
}

Demo

package demo;

import mapper.UserMapper;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import pojo.User;
import utils.MyBatisUtils;

public class Demo {
    @Test
    public void fun(){
        //封装工具类后，就可以直接拿到 SqlSession 对象
        SqlSession sqlSession = MyBatisUtils.getSqlSession();

        //获取 UserMapper 接口
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

        //调用方法，执行依赖的 sql 语句
        User user = userMapper.selectUserById(1);
        System.out.println(user);
    }
}