MyBatis项目所引用的一切依赖jar包和自定义设置
Maven的依赖jar包：
<!--导入依赖-->
<dependencies>
<!--mysql驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</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>
<!--Log4j日志输出功能-->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<!--Lombok实体POJO类简写支持-->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.10</version>
</dependency>
<!--缓存机制-->
<dependency>
<groupId>org.mybatis.caches</groupId>
<artifactId>mybatis-ehcache</artifactId>
<version>1.1.0</version>
</dependency>
</dependencies>
配置文件导出问题：
<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>
Maven的java版本设置问题：
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.encoding>UTF-8</maven.compiler.encoding>
<java.version>11</java.version>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
</properties>
MyBatis操作的工具类MybatisUtils.java:
package com.kuang.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--->SessionFactory
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，我们就可以从中获得 SqlSession 的实例了。
// SqlSession 完全包含了面向数据库执行 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。
public static SqlSession getSqlSession(){
return sqlSessionFactory.openSession();
}
}
工具类在测试时如何正确使用：
@Test
public void test(){
//第一步：获得SqlSession对象
SqlSession sqlSession = MybatisUtils.getSqlSession();
//执行SQL 方式一:getMapper
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> userList = mapper.getUserList();
for (User user : userList) {
System.out.println(user);
}
//关闭SqlSession
sqlSession.close();
}
***Mapper.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=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.kuang.dao.StudentMapper">
<!--思路：
1.查询所有的学生信息
2.根据查询出来的tid，寻找对应的老师-->
<select >
select * from mybatis.student
</select>
<resultMap >
<result column="id" property="id"/>
<result column="name" property="name"/>
<!--复杂的属性，我们需要单独处理
对象：association
集合：collection
-->
<association column="tid" property="teacher" javaType="Teacher" select="getTeacher"/>
</resultMap>
<select >
select * from mybatis.teacher where id=#{tid}
</select>
<!--按照结果嵌套处理-->
<select >
select s.id sid,s.name sname,t.name tname
from mybatis.student s,mybatis.teacher t
where s.tid=t.id;
</select>
<resultMap >
<result column="sid" property="id"/>
<result column="sname" property="name"/>
<association property="teacher" javaType="Teacher">
<result column="tname" property="name"/>
</association>
</resultMap>
</mapper>
MyBatis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核心配置文件-->
<configuration>
<!--引入外部配置文件-->
<properties resource="db.properties"/>
<settings>
<!--标准的日志工厂实现-->
<setting name="logImpl" value="STDOUT_LOGGING"/>
<!--是否自动开启驼峰命名规则映射-->
<setting name="mapUnderscoreToCamelCase" value="true"/>
<!--显示的开启全局缓存-->
<setting name="cacheEnabled" value="true"/>
</settings>
<!--可以给实体类起别名-->
<!-- <typeAliases>-->
<!-- <typeAlias alias="Student" type="com.kuang.pojo.Student"/>-->
<!-- <typeAlias alias="Teacher" type="com.kuang.pojo.Teacher"/>-->
<!-- </typeAliases>-->
<!--environments配置环境组-->
<!--default默认环境-->
<environments default="development">
<!--environment单个环境-->
<environment >
<!--transactionManager配置事务管理器-->
<transactionManager type="JDBC"/>
<!--配置连接池-->
<dataSource type="POOLED">
<property name="driver" value="${driver}"/>
<property name="url" value="${url}"/>
<property name="username" value="${username}"/>
<property name="password" value="${password}"/>
</dataSource>
</environment>
</environments>
<!--绑定接口-->
<mappers>
<mapper resource="com/kuang/dao/UserMapper.xml"/>
</mappers>
</configuration>
db.properties：
driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=utf-8
username=root
password=a1b2c3