【mybatis】学习笔记 1配置 搭建 入门案例

将接口，普通的java对象映射成数据库中的记录 mybatis 简化 jdbc


JDBC的数据连接

package com.mybatis;
 
import java.sql.*;
 
 
public class sql {
	public static void main(String[] args) {
		
	
	Connection con  = null;								//连接对象	
	
	PreparedStatement prs = null;						//查询对象
	
	ResultSet rs = null; 								//结果集
 
	try {
		Class.forName("com.mysql.cj.jdbc.Driver");      //加载驱动类
		
		String url = "jdbc:mysql://localhost:3306/ssm_mybatis?serverTimezone=UTC";
		String user ="root";
		String password = "88888888";
		con = DriverManager.getConnection(url, user, password);///获取连接
		
		String sql = "select * from user where u_sex = ?"; 
		prs = con.prepareStatement(sql);
		prs.setInt(1,0);
		
		rs = prs.executeQuery();	  					//输出结果 
		while(rs.next()) {
			System.out.println(rs.getString("u_id") +" "+rs.getString("u_username"));
		}
	}
	catch (Exception e) {
		// TODO Auto-generated catch block
		System.out.println("连接异常");
	}
	finally {
		try {
			rs.close();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		try {
			prs.close();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		try {
			con.close();
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		
	}
}
}

mybatis

导包 ：

配置文件

http://www.mybatis.org/mybatis-3/zh/getting-started.html（映射sql文件 以及配置文件）
约束导入 通过下面的方法

通过ID 修改数据库

https://www.imooc.com/qadetail/248450?lastmedia=1
sqlMapConfig.xml 的配置

<?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"/>
      <!-- 小型配置文件的相对路径 以及 driver =url 的值!!!!!! -->
      <dataSource type="POOLED"><!-- 连接池连接数据库 -->
        <property name="driver" value="com.mysql.cj.jdbc.Driver"/><!-- 加载驱动类 -->
        <property name="url" value="jdbc:mysql://localhost:3306/ssm_mybatis?serverTimezone=UTC"/><!-- useSSL=false -->
        <property name="username" value="root"/>
        <property name="password" value="88888888"/>
      </dataSource>
    </environment>
  </environments>	
  <mappers>
    <mapper resource="mapper/UserMapper.xml"/><!-- 复制导入mapper -->
  </mappers>
</configuration>

userdao类： 变量要用包装类！！！

package com.bean;
 
import java.util.Date;
 
public class user {
	//用包装类 减少一些问题
 
	private Integer u_id;
	private String u_username;
	private String u_password;
	private String u_sex;
	private Integer u_cid;
	private Date u_createtime;
 
	public Integer getU_id() {
		return u_id;
	}
 
	public void setU_id(Integer u_id) {
		this.u_id = u_id;
	}
 
	public String getU_username() {
		return u_username;
	}
 
	public void setU_username(String u_username) {
		this.u_username = u_username;
	}
 
	public String getU_password() {
		return u_password;
	}
 
	public void setU_password(String u_password) {
		this.u_password = u_password;
	}
 
	public String getU_sex() {
		return u_sex;
	}
 
	public void setU_sex(String u_sex) {
		this.u_sex = u_sex;
	}
 
	public Integer getU_cid() {
		return u_cid;
	}
 
	public void setU_cid(Integer u_cid) {
		this.u_cid = u_cid;
	}
 
	public Date getU_createtime() {
		return u_createtime;
	}
    public void setU_createTime(Date u_createTime) {
		this.u_createTime = u_createTime;
	}
	@Override
	public String toString() {
		return "dao [u_id=" + u_id + ", u_username=" + u_username + ", u_password=" + u_password + ", u_sex=" + u_sex
				+ ", u_cid=" + u_cid + ", u_createtime=" + u_createtime + "]";
	}	
}

userMapper.xml 查询文件的配置！！！

<?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="UserMapper">
  <select id="selectUserById" parameterType="Integer" resultType="com.bean.user">
 	 select * from user where u_id = #{id}
  </select>	 
</mapper>

测试类：

package com.mybatis;
import java.io.IOException;
import java.io.InputStream;
 
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 org.junit.Test;
import com.bean.user;
 
public class test {
	@Test 																// 通过id 查询用户
	public void test() throws IOException {
		String resource = "sqlMapConfig.xml";
		
		InputStream in = Resources.getResourceAsStream(resource); 		// 读出配置文件
		
		SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();	// 创建sqlsession Factory Builder	
		
		SqlSessionFactory ssf= ssfb.build(in); 						// 生产一个sqlsessionfactor
		
		SqlSession session = ssf.openSession();;
		//sql语句的查询
		user s = session.selectOne("UserMapper.selectUserById",1); 		// 操作数据库 
		System.out.println(s);
	}
 
}

用户名模糊查找！！！

 <select id="selectUserByName" parameterType="String" resultType="com.bean.user">
 	 select * from user where u_username like '%${value}%'
  </select>	
List<user> s = session.selectList("UserMapper.selectUserByName","王"); 		// 操作数据库 
		for(user e : s) {											//foreach 输出
			System.out.println(e);
		}

报警告WARNING: An illegal reflective access operation has occurred版本太高

字符串拼接${value} 跟占位符的区别 #{id}
字符串拼接易发生异常注入问题 1=1
要改写为占位符                   ${value}      =>      "%"#{value}"%"
添加一个用户
事务要提交！！！！
小心userdao 不要错了  大小写问题 ！！！Date错了找了好久!!!   跟数据库的字段大小一致！！！

                user u  = new user();
		u.setU_username("陈耿聪");
		u.setU_password("820882");
		u.setU_sex("1");
		u.setU_cid(1);
		
		session.insert("UserMapper.insertUser",u); 		// 操作数据库 
		session.commit();

插入配置的语句

 <insert id="insertUser" parameterType="com.bean.user">
  insert into user values(null , #{u_username},#{u_password},#{u_sex},null,#{u_cid})
  </insert>

修改用户

        	user u  = new user();
		u.setU_id(13);
		u.setU_username("cznczai");
		session.update("UserMapper.updateUser",u); 		// 操作数据库 
		session.commit();

配置文件为

<update id="updateUser" parameterType="com.bean.user">
  update user set u_username = #{u_username} where u_id = #{u_id}
  </update>

删除用户

		u.setU_username("陈耿聪");
		session.delete("UserMapper.deleteUserByname",u); 		// 操作数据库 
		session.commit();

配置文件：

 <delete id="deleteUserByname" parameterType="String>
 	delete from user where u_username = #{u_username}
  </delete>
mybatis DAO开发！！！
UserMapper.xml和SqlMapConfig.xml 依旧不变

userdao.class

package com.my.dao;
 
import com.bean.user;
 
public interface userdao {
	//根据查询id用户
	public user getId(Integer id) ;
}

userdaoImpl.class

把之前test 文件进行拆分

package com.my.dao;
 
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
 
import com.bean.user;
 
															//ctrl + shift + o 删除没用到的包
public class userdaoImpl implements userdao {
	private SqlSessionFactory ssf;							//sqlSessionFactory
	//alt shift + s  -> Generate Constructor ...... 			//生成构造器
	
	public userdaoImpl(SqlSessionFactory ssf) {						//通过构造器给ssf赋值
		super();
		this.ssf = ssf;
	}
 
	public user getId(Integer id)  {
		SqlSession session = ssf.openSession();
		return session.selectOne("UserMapper.selectUserById",id);
	}
 
}

userdaoTest

package com.mybatis;
 
import java.io.IOException;
import java.io.InputStream;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import com.bean.user;
import com.my.dao.userdao;
import com.my.dao.userdaoImpl;
 
public class UserDaoTest {
	
	private static SqlSessionFactory ssf;
	static {
		try {
			InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
			SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
			ssf = ssfb.build(in);
			in.close();
 
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	@Test
	public void DaoTest() {
		userdao Dao = new userdaoImpl(ssf);
		user u = Dao.getId(1);
		System.out.println(u);
	}
}

重复代码进行合并 并简化操作代码 剩下两行！！！！

mybatis >> jdbc
spell报错 拼写报错可以屏蔽

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原文地址：https://www.cnblogs.com/cznczai/p/11155899.html