搭建文件目录
image.png
搭建步骤
- 链接数据库并在pom.xml中导入Mybatis以及Mysql的jar包
- 在父工程中统一导入依赖
- 父工程pom.xml文件
<?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>
<!-- 父工程-->
<groupId>org.example</groupId>
<artifactId>idea_Mybatis_study</artifactId>
<packaging>pom</packaging>
<version>1.0-SNAPSHOT</version>
<modules>
<module>mybatis_01</module>
</modules>
<!-- 导入依赖-->
<dependencies>
<!-- mysql-->
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.21</version>
</dependency>
<!--mybatis-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.2</version>
</dependency>
<!-- junit-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>
<!-- 在build中配置resources，来防止我们资源导出失败的问题-->
<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>
</project>
- 子工程pom.xml文件
<?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">
<parent>
<artifactId>idea_Mybatis_study</artifactId>
<groupId>org.example</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>mybatis_01</artifactId>
<!-- 在build中配置resources，来防止我们资源导出失败的问题-->
<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>
</project>
- 建造工具类：获取sqlSessionFactory类
package com.howe.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 1.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。
public static SqlSession getSqlSession() {
// SqlSession sqlSession = sqlSessionFactory.openSession();
// return sqlSession;
return sqlSessionFactory.openSession();
}
}
- 编写mybatis-config.xml配置文件
- 链接数据库
- 注册每一个Mapper.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"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=utf-8"/>
<property name="username" value="root"/>
<property name="password" value="1998"/>
</dataSource>
</environment>
</environments>
<!--每一个Mapper.xml文件都需要注册，注意中间分割不是“.”-->
<mappers>
<mapper resource="com/howe/dao/UserMapper.xml"></mapper>
</mappers>
</configuration>
- 实体类书写
package com.howe.pojo;
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;
}
<!--此处省略getter()、setter()方法-->
}
- 接口书写
package com.howe.dao;
import com.howe.pojo.User;
import java.util.List;
public interface UserDao {//类名称建议写成和相应的xml文件名相同--->UserMapper
List<User> getUserList();
}
- Mapper.xml文件书写--->代替原来的实现类
<!-- 名字要尽可能和接口名称相同-->
<?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绑定接口 -->
<mapper namespace="com.howe.dao.UserDao">
<!--id 绑定方法，resultType绑定方法返回值类型-->
<select id="getUserList" resultType="com.howe.pojo.User">
<!-- 示例执行的sql语句-->
select * from mybatis.user
</select>
</mapper>
- 测试文件
package com.howe.dao;
import com.howe.pojo.User;
import com.howe.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class UserDaoTest {
@Test
public void Test(){
//第一步获得getSqlSession对象
SqlSession sqlSession = MybatisUtils.getSqlSession();
//执行Sql 方式一：getMapper
// UserDao mapper = sqlSession.getMapper(UserDao.class);
// List<User> userList = mapper.getUserList();
//方式二：老方法selectList
List<User> userList = sqlSession.selectList("com.howe.dao.UserDao.getUserList");
//输出结果
for (User user : userList) {
System.out.println(user);
}
//关闭sqlSession
sqlSession.close();
}
}
常见问题
1.配置文件没有注册
2.绑定接口错误（没有namespace）
3.方法名存在问题
4.返回类型存在问题
5.maven导出资源问题
重点内容
image.png
image.png
