环境:
回顾:
SSM框架:配置文件。最好的方式:看官网文档 https://mybatis.org/mybatis-3/zh/index.html
如果获得Mybatis
Maven仓库:
<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis --> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.4.6</version> </dependency>
github
数据持久化
为什么需要持久化?
Dao层,Service层,controller层。。。
最重要的一点:使用的人多!
思路:搭建环境--->导入Mybatis--->编写代码---->测试!
搭建数据库
CREATE TABLE `user`( `id` INT(20) NOT NULL PRIMARY KEY, `name` VARCHAR(30) DEFAULT NULL , `pwd` VARCHAR(30) DEFAULT NULL )ENGINE=INNODB DEFAULT CHARSET=utf8; INSERT INTO `user`(`id`,`name`,`pwd`) VALUES (1,'张三','123456'), (2,'李四','123456'), (3,'王五','123890')
新建项目
新建一个普通的maven项目
删除src目录
导入maven依赖
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.sheng</groupId> <artifactId>Mybatis-01</artifactId> <version>1.0-SNAPSHOT</version> <!--导入依赖--> <dependencies> <!--mysql驱动--> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.22</version> </dependency> <!--mybatis--> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.4.6</version> </dependency> <!--junit--> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> </dependency> </dependencies> <build> <resources> <resource> <directory>src/main/resources</directory> <includes> <include>**/*.properties</include> <include>**/*.xml</include> </includes> <filtering>true</filtering> </resource> <resource> <directory>src/main/java</directory> <includes> <include>**/*.properties</include> <include>**/*.xml</include> </includes> <filtering>true</filtering> </resource> </resources> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-resources-plugin</artifactId> <configuration> <encoding>UTF-8</encoding> </configuration> </plugin> </plugins> </build> </project>
编写mybatis的核心配置文件
<?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/Mybatis?serverTimezone=UTC"/> <property name="username" value="root"/> <property name="password" value="sxf000218"/> </dataSource> </environment> </environments> <mappers> <mapper resource="com/sheng/dao/UserMapper.xml"/> </mappers> </configuration>
编写mybatis的工具类
package com.sheng.dao.com.sheng.utils.com.sheng.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; //sqlSessionFactory --> sqlSession public class MybatisUtils { private static SqlSessionFactory sqlSessionFactory; static { try { //使用Mybatis第一步:获取sqlSessionFactory对象 String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { e.printStackTrace(); } } //既然有了 SqlSessionFactory,顾名思义,我们可以从中获得 SqlSession 的实例。 // SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。 // 你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句。例如: public static SqlSession getSqlSession(){ return sqlSessionFactory.openSession(); } }
实体类
package com.sheng.pojo; //实体类 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; } @Override public String toString() { return "User{" + "id=" + id + ", name='" + name + '\'' + ", pwd='" + pwd + '\'' + '}'; } }
Dao接口
public interface UserDao { List<User> getUserList(); }
接口实现类由原来的UserDaoImpl转变为一个Mapper配置文件
<?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=绑定一个Dao/Mapper接口--> <mapper namespace="com.sheng.dao.UserDao"> <!--select查询语句--> <select id="getUserList" resultType="com.sheng.pojo.User"> select * from mybatis.user; </select> </mapper>
注意点:
org.apache.ibatis.binding.BindingException: Type interface com.sheng.dao.UserDao is not known to the MapperRegistry.
MapperRegistry是什么?
核心配置文件中注册mappers
junit测试
import java.util.List; public class UserDaoTest { @Test public void test(){ //第一步:获得sqlSession对象 SqlSession sqlSession = MybatisUtils.getSqlSession(); //方式一:getMapper UserDao userDao = sqlSession.getMapper(UserDao.class); List<User> userList = userDao.getUserList(); for (User user : userList){ System.out.println(user); } //关闭sqlSession sqlSession.close(); } }
可能会遇到的问题