mybatis入门

1、首先介绍一个代码自动生成工具

链接：https://pan.baidu.com/s/1pX2FaSCnBtsVDz1grhUUfw 
提取码：yq4t 
 

2、下载后导入eclipse

按照注解修改xml文件

3、运行然后刷新，获得自动生成的代码

4、新建一个maven项目，添加mybatis所需依赖

<!-- log4j -->
	<dependencies>
		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-log4j12</artifactId>
			<version>1.6.6</version>
		</dependency>
		<!-- mybatis -->
		<dependency>
			<groupId>org.mybatis</groupId>
			<artifactId>mybatis</artifactId>
			<version>3.5.1</version>
		</dependency>
		<!-- MySql -->
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>5.1.44</version>
		</dependency>
	</dependencies>
	
	<!-- jdk -->
	<build>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.1</version>
				<configuration>
					<source>1.8</source>
					<target>1.8</target>
				</configuration>
			</plugin>
		</plugins>
	</build>

5、新建如图包或文件，将自动生成的代码放入

 

6、添加所需配置文件mb.xml和log4j.properties

mb.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="dev">
		<environment id="dev">
			<transactionManager type="JDBC" />
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver" />
				<property name="url" value="jdbc:mysql://localhost:3306/bank?characterEncoding=utf8" />
				<property name="username" value="root" />
				<property name="password" value="123456" />
			</dataSource>
		</environment>
	</environments>
	<mappers>
		<mapper resource="mapper/UserMapper.xml"/>
	</mappers>
</configuration>

log4j.properties

log4j.rootLogger=INFO,A3,A1

# A1 \u5F80\u63A7\u5236\u53F0\u4E0A\u6253
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=[%p] [%l] %10.10c - %m%n

log4j.appender.A3=org.apache.log4j.DailyRollingFileAppender 
log4j.appender.A3.file=backup.log 
log4j.appender.A3.DatePattern='.'yyyy-MM-dd
log4j.appender.A3.MaxFileSize=1024KB
log4j.appender.A3.MaxBackupIndex=10
log4j.appender.A3.layout=org.apache.log4j.PatternLayout
log4j.appender.A3.layout.ConversionPattern=\n\n[%-5p] %d{yyyy-MM-dd HH\:mm\:ss,SSS} method\:%l%n%m%n

7、新建

SessionFactory.java

package com.test.utils;

import java.io.IOException;
import java.io.InputStream;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

// 专门生成sqlSession对象的工厂
// sqlSession(一级缓存) 暂时认为是对数据库的连接对象（Conncetion）
public class SessionFactory {
	
	private static ThreadLocal<SqlSession> threadLocal;
	//2 session 工厂
	private static SqlSessionFactory factory;
	
	static {
		threadLocal = new ThreadLocal<>();
		//1 丛配置文件中 读取 对数据库的连接的信息
		InputStream in = null;
		try {
			in = Resources.getResourceAsStream("mb.xml");
			//通过读出来的 连接信息 去初始化 session工厂
			// SqlSessionFactoryBuider 创建SqlSessionFactory
			factory = new SqlSessionFactoryBuilder().build(in);
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			if(in!=null){
				try {
					in.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
	}
	
	// 获得一个session
	public static SqlSession getSession() {
		SqlSession session = threadLocal.get();
		if(session==null) {
			// 创建一个session
			session = factory.openSession();
			// 把session放入threadLocal
			threadLocal.set(session);
		}
		return session;
	}
	
	
	// 关闭session
	public static void closeSession() {
		SqlSession session = threadLocal.get();
		if(session!=null) {
			session.close();
			threadLocal.set(null);
		}
	}

}

8、编写测试类

package com.test.test;

import org.apache.ibatis.session.SqlSession;

import com.test.entity.User;
import com.test.mapper.UserMapper;
import com.test.utils.SessionFactory;

public class TestMybatis {
	public static void main(String[] args) {
		SqlSession session = SessionFactory.getSession();
		UserMapper userMapper = session.getMapper(UserMapper.class);
		User user = userMapper.selectByPrimaryKey(1);
		System.out.println(user.getAccount());
	}
}