mybatis连接mysql数据库
1.创建一个空的maven项目
2.在项目的pom.xml文件中导入所需要的依赖,依赖如下:
没有配置镜像的会导入较慢
<dependencies>
<!--数据库驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.9</version>
</dependency>
<!--mybatis-->
<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.5</version>
</dependency>
<!--单元测试-->
<!-- https://mvnrepository.com/artifact/junit/junit -->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13</version>
<scope>test</scope>
</dependency>
</dependencies>
此外还需要导入过滤文件的xml代码,如下:
<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>
</build>
<!--设置字符集-->
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
自动导入之后看这里有没有依赖包,没有的话就说明没导入成功:
3、创建数据库表
mysql创建数据库表语句:
CREATE TABLE users(
ID INT(10) NOT NULL AUTO_INCREMENT COMMENT ‘用户id‘,
Name VARCHAR(100) NOT NULL COMMENT ‘用户名‘,
Age INT(11) NOT NULL COMMENT ‘年龄‘,
KEY ID (ID)
)ENGINE=INNODB DEFAULT CHARSET=utf8
添加数据语句:
INSERT INTO users (ID,Name,AGE) VALUES
(1,‘小明‘,10),
(2,‘小蓝‘,3),
(3,‘小黄‘,4),
(4,‘小绿‘,2);
数据库表:
4、实体类
public class User {
//字段名与数据库保持一致
private int ID;
private String Name;
private int Age;
//有参和无参构造方法
public User(int ID, String name, int age) {
this.ID = ID;
Name = name;
Age = age;
}
public User() {
}
//get and set 方法
public int getID() {
return ID;
}
public void setID(int ID) {
this.ID = ID;
}
public String getName() {
return Name;
}
public void setName(String name) {
Name = name;
}
public int getAge() {
return Age;
}
public void setAge(int age) {
Age = age;
}
//toString方法
@Override
public String toString() {
return "User{" +
"ID=" + ID +
", Name=‘" + Name + ‘\‘‘ +
", Age=" + Age +
‘}‘;
}
}
5、dao层的UserDao接口方法和Mapper配置文件
dao层的接口:
package com.ma.dao;
import com.ma.pojo.User;
import java.util.List;
public interface UserDao {
List<User> getList();
}
dao层的配置文件:
配置文件可以去官网查找:https://mybatis.org/mybatis-3/zh/index.html
<?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="com.ma.dao.UserDao">
<select id="getList" resultType="com.ma.pojo.User">
select * from users
</select>
</mapper>
注意:配置文件与接口要在同一个包下,否则配置文件扫描接口时无法扫描接口的方法
6、mybatis的配置文件
在resources资源包下创建一个mybatis-config.xml的mybatis配置文件,配置文件的模板官网有提供,也可以自行去官网查找
<?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"><!--使用默认的配置-->
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/text?useSSL=true&userUnicode=true&characterEncoding=UTF-8"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/ma/dao/UserMapper.xml"/>
</mappers>
</configuration>
7、mybatis的java工具类
创建一个工具类的包,在工具类的包中创建一个mybatis工具类,用于连接数据库
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 MybatisUtil {
private static SqlSessionFactory sqlSessionFactory; //实例化sqlSessionFactory工厂
static {
try {
//使用MyBatis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();
}
}
//获取SqlSessiond对象
public static SqlSession getSqlSession() {
return sqlSessionFactory.openSession();
}
}
8、测试
public class MyTest {
@Test
public void Test1(){
//第一步:获取sqlSession对象
SqlSession sqlSession = MybatisUtil.getSqlSession();
//第二步:执行sql
UserDao mapper = sqlSession.getMapper(UserDao.class);
//第三步:执行方法
List<User> userList = mapper.getList();
//第四步:循环打印
for (User user : userList) {
System.out.println(user);
}
//第五步:关闭sqlSession
sqlSession.close();
}
}
9、结果
10、结构
11、几个常用的网址
1、maven仓库:https://mvnrepository.com
2、spring官方文档:https://docs.spring.io/spring/docs/5.2.7.RELEASE/spring-framework-reference/core.html
3、mybatis官网:https://mybatis.org/mybatis-3/zh/index.html