Mybatis之入门（简单配置）
注意
在xml配置文件中，url中的&符号需要转义成 &
1.新建maven项目
<?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>
<properties>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
<groupId>MybatisOnIdeaFirst</groupId>
<artifactId>MybatisOnIdeaFirst</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.3.0</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.8-dmr</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.12</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.12</version>
</dependency>
</dependencies>
</project>目录结构
2.编写数据库配置文件
db.properties (因为不是配置在xml中 所以这里的&可以不使用转义前的形式)
jdbc.username=root
jdbc.password=mysql123
jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/login?useUnicode=true&characterEncoding=utf8&useSSL=false编写Mybatis的配置文件
注意事项
上述代表了数据库配置资源文件的位置（相对位置）
<property name="driver" value="${jdbc.driver}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />使用表达式将值从配置文件中取出来。（也可以直接写入相应的值，注意&会被转义，但是这样程序的可扩展性不够强）
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>
<properties resource="db.properties"/>
<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>
</environments>
<mappers>
<mapper resource="mapper/User.xml"/>
</mappers>
</configuration><?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">
<select id="findById" resultType="model.User" parameterType="int">
select name,password from user where id = #{id}
</select>
</mapper>3.log4j的配置文件
log4j.rootLogger=debug, stdout, R
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p - %m%n
log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=firestorm.log
log4j.appender.R.MaxFileSize=100KB
log4j.appender.R.MaxBackupIndex=1
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n
log4j.logger.com.codefutures=DEBUG4.设计对象-实体映射类
关系 DDL
+———-+————-+——+—–+———+—————-+
| Field | Type | Null | Key | Default | Extra |
+———-+————-+——+—–+———+—————-+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(20) | YES | | NULL | |
| password | varchar(20) | YES | | NULL | |
+———-+————-+——+—–+———+—————-+
User.java
package model;
public class User {
private String name;
private String password;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "User{" +
"name='" + name + '\'' +
", password='" + password + '\'' +
'}';
}
}5.创建一个生成session的工具类
作用
该工具类封装好通过MyBati的工厂获取session的方法，使得操作对数据库进行操作时更加清晰
MyBaticUtils.java
package com.study.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.InputStream;
public class MybatisUtils {
private static SqlSession sqlSession;
static{
try {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
sqlSession = sqlSessionFactory.openSession();
}catch (Exception e){
e.printStackTrace();
}
}
public static SqlSession getSqlSession(){
return sqlSession;
}
}
代码分析
// //xml配置文档的路径
// String resource = "mybatis-config.xml";
// //打开资源
// InputStream inputStream = Resources.getResourceAsStream(resource);
//
// //SqlSessionFactory 工厂可以通过SqlSessionFactoryBuilder().build()传入配置文件的流对象来霍格
// SqlSessionFactory sqlSessionFactory =
// new SqlSessionFactoryBuilder().build(inputStream);
//
// //通过SqlSessionFactory（）实例的open Session（）方法可以获得 session对象 ：可直接操作数据库的对象
// SqlSession sqlSession = sqlSessionFactory.openSession();6.操作数据库
通过主函数测试是否连接数据库成功并完成查询
Main.java
package test;
import model.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 util.MybatisUtils;
import java.io.InputStream;
public class Main {
public static void main(String[] args)throws Exception {
SqlSession sqlSession = MybatisUtils.getSqlSession();
User user = sqlSession.selectOne("com.findById",2);
sqlSession.commit();
System.out.println(user);
}
}
