MyBatis学习(一)入门程序

拼搏现实的明天。 2023-07-20 13:38 12阅读 0赞

## 简介 ##

MyBatis本是apache的一个开源项目iBatis, 2010年这个项目由apache software foundation 迁移到了google code，并且改名为MyBatis 。它支持普通 SQL查询，存储过程和高级映射的优秀持久层框架。MyBatis 消除了几乎所有的JDBC代码和参数的手工设置以及结果集的检索。MyBatis 使用简单的 XML或注解用于配置和原始映射，将接口和 Java 的POJO（Plain Old Java Objects，普通的Java对象）映射成数据库中的记录。  
MyBatis流行的主要原因在于它的简单性和易用性。在Java应用程序中，数据持久化层涉及到的工作有：将从数据库查询到的数据生成所需要的Java对象；将Java对象中的数据用SQL持久化到数据库中。

## 配置 ##

1、jar包  
  1.1下载jar包，然后解压  
[https://github.com/mybatis/mybatis-3/releases/tag/mybatis-3.2.7][https_github.com_mybatis_mybatis-3_releases_tag_mybatis-3.2.7]  
  1.2 Maven

<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    	<modelVersion>4.0.0</modelVersion>
    	<groupId>com.ls</groupId>
    	<artifactId>mybatis1009</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    	<dependencies>
    		 <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.4.6</version> </dependency>  <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.17</version> </dependency>  <dependency> <groupId>commons-logging</groupId> <artifactId>commons-logging</artifactId> <version>1.2</version> </dependency>  <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.13</version> </dependency>  <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> <scope>test</scope> </dependency>
    	</dependencies>
    </project>

mysql 的版本选择对应的；junit用于测试，可不加。  
2、配置log4j日志配置文件

# Global logging configuration
    log4j.rootLogger=DEBUG, stdout
    # Console output...
    log4j.appender.stdout=org.apache.log4j.ConsoleAppender
    log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
    log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

3、配置mybatis的全局配置文件sqlMapConfig.xml  
此配置文件，文件名称不固定，可由开发人员自己指定，同样配置在config目录下，如下所示：

<?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>
    	 <settings> <setting name="logImpl" value="LOG4J" /> <setting name="lazyLoadingEnabled" value="true" /> <setting name="aggressiveLazyLoading" value="false" /> <setting name="cacheEnabled" value="true" /> </settings>
    	
    	 <environments default="mysqlenv"> <environment id="mysqlenv"> <transactionManager type="JDBC" /> <dataSource type="POOLED"> <property name="driver" value="com.mysql.cj.jdbc.Driver" /> <property name="url" value="jdbc:mysql://localhost:3306/ssm?useSSL=false&serverTimezone=Hongkong" /> <property name="username" value="root" /> <property name="password" value="123456" /> </dataSource> </environment> </environments>
    	
    </configuration>

## 入门程序 ##

1、创建配置SQL语句的mapper.xml映射文件

<?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="worker">
    
    	 <select id="queryWorker" parameterType="String" resultType="com.ls.bean.Worker"> select * from worker where wid = #{value} </select>
    
    	 <update id="updateWorker" parameterType="com.ls.bean.Worker"> update worker set age = #{age} where wname = #{wname} </update>
    </mapper>

2、创建mapper.xml映射文件对应的Java Bean

package com.ls.bean;
    
    public class Worker { 
    	private String wid;
    	private String wname;
    	private Integer age;
    	private String sex;
    	public Worker() { 
    	}
    	public String getWid() { 
    		return wid;
    	}
    	public void setWid(String wid) { 
    		this.wid = wid;
    	}
    	public String getWname() { 
    		return wname;
    	}
    	public void setWname(String wname) { 
    		this.wname = wname;
    	}
    	public Integer getAge() { 
    		return age;
    	}
    	public void setAge(Integer age) { 
    		this.age = age;
    	}
    	public String getSex() { 
    		return sex;
    	}
    	public void setSex(String sex) { 
    		this.sex = sex;
    	}
    	public Worker(String wid, String wname, Integer age, String sex) { 
    		super();
    		this.wid = wid;
    		this.wname = wname;
    		this.age = age;
    		this.sex = sex;
    	}
    	@Override
    	public String toString() { 
    		return "Worker [wid=" + wid + ", wname=" + wname + ", age=" + age + ", sex=" + sex + "]";
    	}
    }

3、配置sqlMapConfig.xml文件  
为了让配置的mapper.xml文件起作用，那么需要在mybatis的全局配置文件sqlMapConfig.xml中加载该文件  
在<configuration></configuration>里添加以下代码：

4、创建测试方法

package com.ls.test;
    
    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;
    import org.junit.After;
    import org.junit.Before;
    import org.junit.Test;
    
    import com.ls.bean.Worker;
    
    public class Test1 { 
    
    	SqlSession session = null;
    
    	@Before
    	public void basic() throws IOException { 
    		//使用Mybatis提供的资源类读取主配置文件
    		InputStream is = Resources.getResourceAsStream("sqlMapConfig.xml");//相对于类路径
    		//工厂构建者
    		SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
    		//工厂构建者通过配置文件得到流构建工厂
    		SqlSessionFactory sqlSessionFactory = ssfb.build(is);
    		//工厂打开到指定数据库的连接
    		session = sqlSessionFactory.openSession();//，，默认不自动提交
    	}
    
    	@After
    	public void close(){ 
    		//会话关闭
    		session.close();
    	}
    
    	@Test
    	public void test1() throws Exception { 
    		Worker w = session.selectOne("worker.queryWorker", "5af9f088-5e5d-11e9-9dc0-28d244d68b7c");
    		System.out.println(w);
    	}
    	@Test
    	public void test2() throws Exception { 
    		Worker w = new Worker();
    		w.setAge(60);
    		w.setWname("郭靖");
    		int row = session.update("worker.updateWorker", w);
    		System.out.println(row+"行受影响");
    		session.commit();
    	}
    }

附：  
sqlMapConfig.xml 完整版

<?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>
    	<settings>
    		<setting name="logImpl" value="LOG4J" />
    		<setting name="lazyLoadingEnabled" value="true" />
    		<setting name="aggressiveLazyLoading" value="false" />
    		<setting name="cacheEnabled" value="true" />
    	</settings>
    	<environments default="mysqlenv">
    		<environment id="mysqlenv">
    			<transactionManager type="JDBC" />
    			<dataSource type="POOLED">
    				<property name="driver" value="com.mysql.cj.jdbc.Driver" />
    				<property name="url"
    					value="jdbc:mysql://localhost:3306/ssm?useSSL=false&serverTimezone=Hongkong" />
    				<property name="username" value="root" />
    				<property name="password" value="123456" />
    			</dataSource>
    		</environment>
    	</environments>
    	<mappers>
    		<mapper resource="WorkerMapper.xml"/>
    	</mappers>
    </configuration>

本文以mysql8为例，mysql5选择对应版本的mysql-connector-java，url与driver也填写mysql5对应的内容。

[https_github.com_mybatis_mybatis-3_releases_tag_mybatis-3.2.7]: https://github.com/mybatis/mybatis-3/releases/tag/mybatis-3.2.7