Mybatis
简介
**
1.什么是Mybatis
**
MyBatis是一款优秀的基于java的持久层框架，它内部
封装了jdbc，使开发者只需要关注sql语句本身。
参考文档 ：https://mybatis.org/mybatis-3/zh/index.html
2.持久化
数据持久化
·持久化就是将程序的数据在持久状态和瞬时状态转换的过程
·内存：断电即失
·数据库(jdbc),io文件持久化
·生活中遇到的持久化：买的肉放时间太长会坏，所以我们买的肉要放到冰箱里冷藏，等吃了在去解冻。
3.持久层
Dao层，Service层，Controller层…
·完成持久化工作的代码块
·层界十分明
CRUD
1.搭建环境
- [ ] 1.搭建数据库
CREATE DATABASE mybatis;
USE mybatis;
CREATE TABLE user(
id int(20) NOT NULL PRIMARY KEY,
name varchar(30) DEFAULT NULL,
pwd varchar(20) DEFAULT NULL
);
INSERT INTO user(id,name,pwd) VALUES
(1,'李李李','123456'),
(2,'华晨宇','666666'),
(3,'苑苑苑','520520');
2.pom.xml
·新建一个普通的maven项目
·删除src目录
3.导入maven依赖 pom.xml
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.6</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.18</version>
</dependency>
</dependencies>
3.CRUD
4.创建一个模块
·编写mybatis的核心配置文件 mybatis-config.xml
<?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.jdbc.Driver"/> <!-- ?useSSL=false-->
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="UserDao.xml"/>
</mappers>
</configuration>
·编写mybatis工具类 MybatisUtils
public class MybatisUtils {//使用mybatis的第一步：获取sqlSessionFactory对象
// private static SqlSessionFactory factory = null;
private static SqlSessionFactory sqlSession;
static {
try {
//使用mybatis第一步、获取sqlSessionFactory对象
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSession = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
public static SqlSession getSqlSession(){
return sqlSession.openSession();
}
}
编写代码
·实体类 User
import lombok.Data;
@Data
public class User {
private Integer id;
private String name;
private String pwd;
public User() {
}
public User(Integer id, String name, String pwd) {
this.id = id;
this.name = name;
this.pwd = pwd;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", name='" + name + '\'' +
", pwd='" + pwd + '\'' +
'}';
}
}
·Dao接口 UserDao
//这个类操作对象的实体
package com.guohui.dao;
import com.guohui.pojo.User;
import java.util.List;
public interface UserDao {
//查询所有用户
List<User> getUserList();
//根据id查询用户
User getUserById(int id);
//添加一个用户
int addUser(User user);
//修改用户
int updateUser(User user);
//根据id删除用户
int deleteUser(int id);
}
·接口实现类 UserDao.xml
<?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">
<!--namespace=绑定对应的Dao/mapper接口-->
<mapper namespace="com.guohui.dao.UserDao">
<!--select查询语句-->
<select id="getUserList" resultType="com.guohui.pojo.User">
select * from user
</select>
<!-- 根据id查询用户-->
<select id="getUserById" parameterType="int" resultType="com.guohui.pojo.User">
select * from user where id = #{id}
</select>
<!-- 添加一个用户-->
<insert id="addUser" parameterType="com.guohui.pojo.User">
insert into user(id, name, pwd) values (#{id},#{name},#{pwd})
</insert>
<!-- 修改用户-->
<update id="updateUser" parameterType="com.guohui.pojo.User">
update user set name=#{name},pwd=#{pwd} where id = #{id}
</update>
<!-- 删除用户-->
<delete id="deleteUser" parameterType="int">
delete from user where id = #{id}
</delete>
</mapper>
·测试.junit测试
public class MyTest {
@Test
public void test(){//查询全部用户
//第一步：获得SqlSession对象
SqlSession sqlSession = MybatisUtils.getSqlSession();
//执行SQL
UserDao mapper = sqlSession.getMapper(UserDao.class);
List<User> userList = mapper.getUserList();
for (User user : userList) {
System.out.println(user);
}
//关闭SqlSession
sqlSession.close();
}
@Test//查询id用户
public void test01(){
//根据id查询用户
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao mapper = sqlSession.getMapper(UserDao.class);
//查询id为1 的用户
User user = mapper.getUserById(1);
System.out.println(user);
sqlSession.close();
}
@Test//添加用户
public void addUser(){
//添加一个用户
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao mapper = sqlSession.getMapper(UserDao.class);
User user = new User(9,"苑雪儿","guohui520");
int i = mapper.addUser(user);
System.out.println("插入成功"+i);
sqlSession.commit(); //提交事务,重点!不写的话不会提交到数据库
sqlSession.close();
}
@Test//修改用户
public void updateUser(){
//添加一个用户
SqlSession sqlSession = MybatisUtils.getSqlSession();
UserDao mapper = sqlSession.getMapper(UserDao.class);
mapper.updateUser(new User(5,"李国辉","520yuanxueer"));
System.out.println("修改成功！");
sqlSession.commit(); //提交事务,重点!不写的话不会提交到数据库
sqlSession.close();
}
@Test//删除用户
public void testDeleteUser() {
SqlSession session = MybatisUtils.getSqlSession();
UserDao mapper = session.getMapper(UserDao.class);
int i = mapper.deleteUser(5);
System.out.println(i);
session.commit(); //提交事务,重点!不写的话不会提交到数据库
session.close();
}
}
谢谢观看，哪里写的有问题可以评论，随时在线修改。
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