Mybatis系列二：全局配置文件

r囧r小猫 2022-04-24 07:44 268阅读 0赞

一、properties  
1、编写dbconfig.properties文件

jdbc.driver=com.mysql.jdbc.Driver
    jdbc.url=jdbc:mysql://localhost:3306/mybatis
    jdbc.username=root
    jdbc.password=root
    
    orcl.driver=oracle.jdbc.OracleDriver
    orcl.url=jdbc:oracle:thin:@localhost:1521:orcl
    orcl.username=scott
    orcl.password=123456

2、使用properties引入dbconfig.properties文件

<properties resource="dbconfig.properties"></properties>
    	<environments default="development">
    		<environment id="development">
    			<transactionManager type="JDBC"></transactionManager>
    			<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>

二、settings

<settings>
    		
    		<setting name="mapUnderscoreToCamelCase" value="true"/>
    	</settings>

三、typeAliases

<typeAliases>
    		
    		
    		
    		
    		<package name="com.atguigu.mybatis.bean"/>
    		
    		
    	</typeAliases>

四、environments

<environments default="dev_mysql">
    	<environment id="dev_mysql">
    		<transactionManager type="JDBC"></transactionManager>
    		<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="dev_oracle">
    		<transactionManager type="JDBC" />
    		<dataSource type="POOLED">
    			<property name="driver" value="${orcl.driver}" />
    			<property name="url" value="${orcl.url}" />
    			<property name="username" value="${orcl.username}" />
    			<property name="password" value="${orcl.password}" />
    		</dataSource>
    	</environment>
    </environments>

五、databaseIdProvider

<databaseIdProvider type="DB_VENDOR">
    	
    	<property name="MySQL" value="mysql"/>
    	<property name="Oracle" value="oracle"/>
    	<property name="SQL Server" value="sqlserver"/>
    </databaseIdProvider>

修改EmployeeMapper.xml文件。databaseId指定数据库厂商的标识。这里也就是我们给数据库厂商起的别名。用来指定sql在哪个数据库下才执行。

<?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.atguigu.mybatis.dao.EmployeeMapper">
    
     	<select id="getEmpById" resultType="com.atguigu.mybatis.bean.Employee">
    		select * from tbl_employee where id = #{id}
    	</select>
    	<select id="getEmpById" resultType="com.atguigu.mybatis.bean.Employee"
    		databaseId="mysql">
    		select * from tbl_employee where id = #{id}
    	</select>
    	<select id="getEmpById" resultType="com.atguigu.mybatis.bean.Employee"
    		databaseId="oracle">
    		select EMPLOYEE_ID id,LAST_NAME	lastName,EMAIL email 
    		from employees where EMPLOYEE_ID=#{id}
    	</select>
    </mapper>

六、mappers

<mappers>
    		
    		
    		
    		
    		
    		<package name="com.atguigu.mybatis.dao"/>
    	</mappers>

1、编写EmployeeMapperAnnotation类

public interface EmployeeMapperAnnotation {
    	
    	@Select("select * from tbl_employee where id=#{id}")
    	public Employee getEmpById(Integer id);
    }

2、编写测试方法

@Test
    	public void test01() throws IOException{
    		String resource = "mybatis-config.xml";
    		InputStream inputStream = Resources.getResourceAsStream(resource);
    		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    		SqlSession openSession = sqlSessionFactory.openSession();
    		try{
    			EmployeeMapperAnnotation mapper = openSession.getMapper(EmployeeMapperAnnotation.class);
    			Employee empById = mapper.getEmpById(1);
    			System.out.println(empById);
    		}finally{
    			openSession.close();
    		}
    	}