MyBatis下载地址
代码结构如下:
pojo/User.java
package com.atguigu.mybatis.pojo;
public class User {
private Integer id;
private String username;
private String password;
private Integer age;
private String sex;
private String email;
//这里省略了有参、无参构造、get、setter、重载toString
}
pom.xml
<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>4.0.0modelVersion>
<groupId>com.atguigu.mybatisgroupId>
<artifactId>MyBatis_demo1artifactId>
<version>1.0-SNAPSHOTversion>
<packaging>jarpackaging>
<dependencies>
<dependency>
<groupId>org.mybatisgroupId>
<artifactId>mybatisartifactId>
<version>3.5.7version>
dependency>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.12version>
<scope>testscope>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>8.0.28version>
dependency>
<dependency>
<groupId>log4jgroupId>
<artifactId>log4jartifactId>
<version>1.2.17version>
dependency>
dependencies>
project>
习惯上命名为
mybatis-config.xml
,这个文件名仅仅只是建议,并非强制要求。将来整合Spring之后,这个配置文件可以省略,所以大家操作时可以直接复制、粘贴。
核心配置文件主要用于配置连接数据库的环境以及MyBatis的全局配置信息
核心配置文件存放的位置是src/main/resources目录下
resources/mybatis-config.xml
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"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="mappers/UserMapper.xml"/>
mappers>
configuration>
核心配置文件中的标签必须按照固定的顺序(有的标签可以不写,但顺序一定不能乱):
properties、settings、typeAliases、typeHandlers、objectFactory、objectWrapperFactory、reflectorFactory、plugins、environments、databaseIdProvider、mappers
DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<properties resource="jdbc.properties" />
<typeAliases>
<package name="com.atguigu.mybatis.pojo"/>
typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
dataSource>
environment>
<environment id="test">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/myDB"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
dataSource>
environment>
environments>
<mappers>
<package name="com.atguigu.mybatis.mapper"/>
mappers>
configuration>
resources/jdbc.properties
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/myDB
jdbc.username=root
jdbc.password=root
默认的类型别名
MyBatis中的mapper接口相当于以前的dao。但是区别在于,mapper仅仅是接口,我们不需要提供实现类
mapper/UserMapper.java
package com.atguigu.mybatis.mapper;
import com.atguigu.mybatis.pojo.User;
import java.util.List;
public interface UserMapper {
/**
* MyBatis面向接口编程的两个一致:
* 1、映射文件的namespace要和mapper接口的全类名保持一致
* 2、映射文件中SQL语句的id要和mapper接口中的方法名一致
*
* 表--实体类--mapper接口--映射文件
*/
/**
* 添加用户信息
*/
int insertUser();
/**
* 修改用户信息
*/
void updateUser();
/**
* 删除用户信息
*/
void deleteUser();
/**
* 根据id查询用户信息
*/
User getUserById();
/**
* 查询所有的用户信息
*/
List<User> getAllUser();
}
Java概念 | 数据库概念 |
---|---|
类 | 表 |
属性 | 字段/列 |
对象 | 记录/行 |
映射文件的命名规则:
resources/mapper/UserMapper.xml
DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.atguigu.mybatis.mapper.UserMapper">
<insert id="insertUser">
insert into t_user values(null,'admin','123456',23,'男','[email protected]')
insert>
mapper>
<update id="updateUser">
update t_user set username = '张三' where id = 4
update>
<delete id="deleteUser">
delete from t_user where id = 5
delete>
<select id="getUserById" resultType="com.atguigu.mybatis.pojo.User">
select * from t_user where id = 3
select>
<select id="getAllUser" resultType="User">
select * from t_user
select>
1. 查询的标签select必须设置属性resultType或resultMap,用于设置实体类和数据库表的映射关系
- resultType:自动映射,用于属性名和表中字段名一致的情况
- resultMap:自定义映射,用于一对多或多对一或字段名和属性名不一致的情况
2. 当查询的数据为多条时,不能使用实体类作为返回值,只能使用集合,否则会抛出异常TooManyResultsException;但是若查询的数据只有一条,可以使用实体类或集合作为返回值
SqlSession:代表Java程序和数据库之间的会话。(HttpSession是Java程序和浏览器之间的会话)
SqlSessionFactory:是“生产”SqlSession的“工厂”
test/MyBatisTest.java
package com.atguigu.mybatis.test;
import com.atguigu.mybatis.mapper.UserMapper;
import com.atguigu.mybatis.pojo.User;
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 org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class MyBatisTest {
/**
* SqlSession默认不自动提交事务,若需要自动提交事务
* 可以使用SqlSessionFactory.openSession(true);
*/
@Test
public void testMyBatis() throws IOException {
//加载核心配置文件
InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
//获取SqlSessionFactoryBuilder
SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
//获取sqlSessionFactory
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);
//获取SqlSession
SqlSession sqlSession = sqlSessionFactory.openSession(true);
//获取mapper接口对象
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
//测试功能
int result = mapper.insertUser();
//提交事务
//sqlSession.commit();
System.out.println("result:"+result);
}
@Test
public void testCRUD() throws IOException {
InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
SqlSession sqlSession = sqlSessionFactory.openSession(true);
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
//mapper.updateUser();
//mapper.deleteUser();
/*User user = mapper.getUserById();
System.out.println(user);*/
List<User> list = mapper.getAllUser();
list.forEach(user -> System.out.println(user));
}
}
SqlSession sqlSession = sqlSessionFactory.openSession(true);
,传入一个Boolean类型的参数,值为true,这样就可以自动提交加入依赖
<dependency>
<groupId>log4jgroupId>
<artifactId>log4jartifactId>
<version>1.2.17version>
dependency>
加入log4j的配置文件
DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
<appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
<param name="Encoding" value="UTF-8" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m (%F:%L) \n" />
layout>
appender>
<logger name="java.sql">
<level value="debug" />
logger>
<logger name="org.apache.ibatis">
<level value="info" />
logger>
<root>
<level value="debug" />
<appender-ref ref="STDOUT" />
root>
log4j:configuration>