二、mybatis全局配置文件说明

中文文档地址:https://mybatis.org/mybatis-3/zh/configuration.html

开始前的准备:

本章实列为 mybatis的简介和helloworld 中helloworld 的实例;

测试可以用helloworld 中test包中的方法测试;

配置顺序,properties settings  typeAliases typeHandlers objectFactory  objectWrapperFactory  reflectFactory plugings  environment databaseIdProvider  mappers 

1.properties:引入外部properties配置文件的内容:

属性:

  • resource:引入类路径下的资源
  • url:引入网络路径或者磁盘路径下的资源
 <properties resource="dbconfig.properties"></properties>

测试

外部文件dbconfig.peoperties

dbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis
jdbc.username=root
jdbc.password=root
View Code

全局文件mybatis-config.xml:

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE configuration
 3   PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-config.dtd">
 5 <configuration>
 6     <!--
 7         1、mybatis可以使用properties来引入外部properties配置文件的内容;
 8         resource:引入类路径下的资源
 9         url:引入网络路径或者磁盘路径下的资源
10       -->
11     <properties resource="dbconfig.properties"></properties>
12   
13   <environments default="development">
14     <environment id="development">
15       <transactionManager type="JDBC"/>
16       <dataSource type="POOLED">
17         <property name="driver" value="${jdbc.driver}" />
18                 <property name="url" value="${jdbc.url}" />
19                 <property name="username" value="${jdbc.username}" />
20                 <property name="password" value="${jdbc.password}" />
21       </dataSource>
22     </environment>
23   </environments>
24   <!-- 将我们写好的SQL映射文件一定注册到全局配置文件中 -->
25   <mappers>
26     <mapper resource="EmployeeMapper.xml"/>
27   </mappers>
28 </configuration>

运行测试类:结果Employee [id=0, lastName=null, email=1602211058@qq.com, gender=女];

2、settings包含很多重要的设置项:

setting:用来设置每一个设置项

属性:

  • name:设置项名
  • value:设置项取值
<settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

这里的 mapUnderscoreToCamelCase为是否开启驼峰命名自动映射,即从经典数据库列名 A_COLUMN 映射到经典 Java 属性名 aColumn,默认值为false .。

测试:

全局文件mybatis-config.xml:

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE configuration
 3   PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-config.dtd">
 5 <configuration>
 6     <!--
 7         1、mybatis可以使用properties来引入外部properties配置文件的内容;
 8         resource:引入类路径下的资源
 9         url:引入网络路径或者磁盘路径下的资源
10       -->
11     <properties resource="dbconfig.properties"></properties>
12     <!-- 
13         2、settings包含很多重要的设置项
14         setting:用来设置每一个设置项
15             name:设置项名
16             value:设置项取值
17      -->
18     <settings>
19         <setting name="mapUnderscoreToCamelCase" value="true"/>
20     </settings>
21   <environments default="development">
22     <environment id="development">
23       <transactionManager type="JDBC"/>
24       <dataSource type="POOLED">
25         <property name="driver" value="${jdbc.driver}" />
26                 <property name="url" value="${jdbc.url}" />
27                 <property name="username" value="${jdbc.username}" />
28                 <property name="password" value="${jdbc.password}" />
29       </dataSource>
30     </environment>
31   </environments>
32   <!-- 将我们写好的SQL映射文件一定注册到全局配置文件中 -->
33   <mappers>
34     <mapper resource="EmployeeMapper.xml"/>
35   </mappers>
36 </configuration>
View Code

修改EmployeeMapper.xml:

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper
 3   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <mapper namespace="aaa">
 6 <!--
 7 namespace:命名空间;
 8 id:唯一标识;
 9 resultType:返回值类型;
10 #{id}:从传递过来的参数中去除ID值
11  -->
12     <select id="getById" resultType="entity.Employee">
13         select LAST_NAME 
14         ,gender as gender,email as email from
15         tbl_employee where id =#{id}
16     </select>
17 </mapper>

运行测试类,结果为:Employee [id=0, lastName=null, email=1602211058@qq.com, gender=女]

3、typeAliases:别名处理器;(较少使用)

sql 映射文件的返回类型 需要添加 全类名,比较长;可以使用别名;typeAliases 别名处理器 可以为我们的java类型起别名,别名不区分大小写;别名处理器可以分两种:

  • typeAlias:为某个java类型起别名
  • package:为某个包下的所有类批量起别名 

typeAlias属性:

  • type:指定要起别名的类型全类名;默认别名就是类名小写;employee
  • alias:指定新的别名
<typeAlias type="com.atguigu.mybatis.bean.Employee" alias="emp"/>

package属性:

name:指定包名(为当前包以及下面所有的后代包的每一个类都起一个默认别名(类名小写),)

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

typeAlias测试:

全局文件mybatis-config.xml:

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE configuration
 3   PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-config.dtd">
 5 <configuration>
 6     <!--
 7         1、mybatis可以使用properties来引入外部properties配置文件的内容;
 8         resource:引入类路径下的资源
 9         url:引入网络路径或者磁盘路径下的资源
10       -->
11     <properties resource="dbconfig.properties"></properties>
12     <!-- 
13         2、settings包含很多重要的设置项
14         setting:用来设置每一个设置项
15             name:设置项名
16             value:设置项取值
17      -->
18     <settings>
19         <setting name="mapUnderscoreToCamelCase" value="true"/>
20     </settings>
21     <!-- 3、typeAliases:别名处理器:可以为我们的java类型起别名 
22             别名不区分大小写
23     -->
24     <typeAliases>
25         <typeAlias type="entity.Employee" alias="emp"/>
26     </typeAliases>
27   <environments default="development">
28     <environment id="development">
29       <transactionManager type="JDBC"/>
30       <dataSource type="POOLED">
31         <property name="driver" value="${jdbc.driver}" />
32                 <property name="url" value="${jdbc.url}" />
33                 <property name="username" value="${jdbc.username}" />
34                 <property name="password" value="${jdbc.password}" />
35       </dataSource>
36     </environment>
37   </environments>
38   <!-- 将我们写好的SQL映射文件一定注册到全局配置文件中 -->
39   <mappers>
40     <mapper resource="EmployeeMapper.xml"/>
41   </mappers>
42 </configuration>
View Code

修改EmployeeMapper.xml:

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper
 3   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <mapper namespace="aaa">
 6 <!--
 7 namespace:命名空间;
 8 id:唯一标识;
 9 resultType:返回值类型;
10 #{id}:从传递过来的参数中去除ID值
11  -->
12     <select id="getById" resultType="emp">
13         select LAST_NAME 
14         ,gender as gender,email as email from
15         tbl_employee where id =#{id}
16     </select>
17 </mapper>

测试结果:Employee [id=0, lastName=JoyLi, email=1602211058@qq.com, gender=女]

 

4、environments:环境们,mybatis可以配置多种环境

default指定使用某种环境。可以达到快速切换环境。

environment:配置一个具体的环境信息;id代表当前环境的唯一标识;必须有两个标签:transactionManager(事务管理器)、dataSource(数据源):

 

transactionManager:事务管理器;

type:事务管理器的类型;JDBC(JdbcTransactionFactory)、MANAGED(ManagedTransactionFactory)、自定义

自定义事务管理器:实现TransactionFactory接口.type指定为全类名

dataSource:数据源;

type:数据源类型; 数据源类型包括有 UNPOOLED(UnpooledDataSourceFactory)、POOLED(PooledDataSourceFactory)、JNDI(JndiDataSourceFactory)、自定义;

自定义数据源:实现DataSourceFactory接口,type是全类名

 1 <environments default="dev_mysql">
 2         <environment id="dev_mysql">
 3             <transactionManager type="JDBC"></transactionManager>
 4             <dataSource type="POOLED">
 5                 <property name="driver" value="${jdbc.driver}" />
 6                 <property name="url" value="${jdbc.url}" />
 7                 <property name="username" value="${jdbc.username}" />
 8                 <property name="password" value="${jdbc.password}" />
 9             </dataSource>
10         </environment>
11     
12         <environment id="dev_oracle">
13             <transactionManager type="JDBC" />
14             <dataSource type="POOLED">
15                 <property name="driver" value="${orcl.driver}" />
16                 <property name="url" value="${orcl.url}" />
17                 <property name="username" value="${orcl.username}" />
18                 <property name="password" value="${orcl.password}" />
19             </dataSource>
20         </environment>
21     </environments>

测试:

全局文件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="dbconfig.properties"></properties>
  <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>
  <!-- 将我们写好的SQL映射文件一定哟啊注册到全局配置文件中 -->
  <mappers>
    <mapper resource="EmployeeMapper.xml"/>
  </mappers>
</configuration>
View Code

修改EmployeeMapper.xml:(这里默认就是访问dev_mysql,如果要切换则更改mybatis-config.xml中的environments default="dev_mysql“中的default 实现快速切换环境)

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper
 3   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <mapper namespace="aaa">
 6 <!-- 
 7 namespace:命名空间;指定为接口的全类名
 8 id:唯一标识;
 9 resultType:返回值类型;
10 #{id}:从传递过来的参数中去除ID值
11  -->
12     <select id="getById" resultType="entity.Employee">
13         select LAST_NAME AS
14         lastName,gender as gender,email as email from
15         tbl_employee where id =#{id}
16     </select>    
17 </mapper>
View Code

外部文件dbconfig.peoperties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mybatis
jdbc.username=root
jdbc.password=

orcl.driver=oracle.jdbc.OracleDriver
orcl.url=jdbc:oracle:thin:@localhost:1521:orcl
orcl.username=scott
orcl.password=123456
View Code

 测试结果:Employee [id=null, lastName=joy2x2, email=joy52112225@iclound.com, gender=女];(结果可能跟上面结果不同,因为不同笔记本的数据库,所以数据有些许不同)

 

5.databaseIdProvider:支持多数据库厂商;

type="DB_VENDOR":vendordatabaseidprovider 

作用就是得到数据库厂商的标识(驱动getDatabaseProductName())

MySQL,Oracle,SQL Server

<databaseIdProvider type="DB_VENDOR">
        <!-- 为不同的数据库厂商起别名 -->
        <property name="MySQL" value="mysql"/>
        <property name="Oracle" value="oracle"/>
        <property name="SQL Server" value="sqlserver"/>
    </databaseIdProvider>

执行SQL语句时可以选择oracle的数据库:

<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>

 测试结果:Employee [id=null, lastName=joy2x2, email=joy52112225@iclound.com, gender=女];(结果可能跟上面结果不同,因为不同笔记本的数据库,所以数据有些许不同)

6、mappers:将sql映射注册到全局配置中

mapper:注册单个

  • 注册配置文件

resource:引用类路径下的SQL映射文件,例如:EmployeeMapper.xml,前面的例子都是这种注册方式,这里不再做例子;

<mapper resource="EmployeeMapper.xml"/>

url:引用网络路径下或者磁盘路径下的SQL映射文件;例如:file:///var/mappers/AutorMapper.xml

  • class:引用注册接口:

1.有SQL映射文件,映射文件名必须接口同名,并且放在与接口同一目录下;

 <mapper class="dao.EmployeeMapper"/>

2.没有SQL映射文件,所有的SQL都是利于注解写在接口上;

推荐:比较重要的、复杂的DAO接口我们来写SQL映射文件

不重要、简单的Dao接口为了开发快速可以使用注解

  

批量注册:

批量注册 有SQL映射文件,映射文件名必须接口同名,并且放在与接口同一目录下;

<package name="dao"/>

 

class:引用注册接口测试:

全局文件mybatis-config.xml:

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE configuration
 3   PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-config.dtd">
 5 <configuration>
 6 <properties resource="dbconfig.properties"></properties>
 7   <environments default="dev_mysql">
 8         <environment id="dev_mysql">
 9             <transactionManager type="JDBC"></transactionManager>
10             <dataSource type="POOLED">
11                 <property name="driver" value="${jdbc.driver}" />
12                 <property name="url" value="${jdbc.url}" />
13                 <property name="username" value="${jdbc.username}" />
14                 <property name="password" value="${jdbc.password}" />
15             </dataSource>
16         </environment>
17     
18         <environment id="dev_oracle">
19             <transactionManager type="JDBC" />
20             <dataSource type="POOLED">
21                 <property name="driver" value="${orcl.driver}" />
22                 <property name="url" value="${orcl.url}" />
23                 <property name="username" value="${orcl.username}" />
24                 <property name="password" value="${orcl.password}" />
25             </dataSource>
26         </environment>
27     </environments>
28   <!-- 将我们写好的SQL映射文件一定哟啊注册到全局配置文件中 -->
29   <mappers>
30     <mapper class="dao.EmployeeMapper"/>
31   </mappers>
32 </configuration>
View Code

目录结构调整:为了让EmployeeMapper.xml 和EmployeeMapper.java在同一个目录下做出如下调整;

修改EmployeeMapper.xml:

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE mapper
 3   PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 5 <mapper namespace="dao.EmployeeMapper">
 6 <!-- 
 7 namespace:命名空间;指定为接口的全类名
 8 id:唯一标识;
 9 resultType:返回值类型;
10 #{id}:从传递过来的参数中去除ID值
11  -->
12     <select id="getById" resultType="entity.Employee">
13         select LAST_NAME AS
14         lastName,gender as gender,email as email from
15         tbl_employee where id =#{id}
16     </select>    
17 </mapper>
View Code

使用接口的测试方法测试;

 1 @Test
 2     public void test01() throws IOException {
 3         String resource = "mybatis-config.xml";
 4         InputStream inputStream = Resources.getResourceAsStream(resource);
 5         // 1.获取SqlSessionFactory对象
 6         SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 7         // 获取SqlSessionFactory 实例,能直接运行已经执行的sql语句
 8         SqlSession openSession = sqlSessionFactory.openSession();
 9         try {
10             // 3.获取接口的实现类对象,当接口和xml文件动态绑定时,MyBatis会为接口自动创建一个代理对象,通过代理对象去调用相应的方法
11             EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
12             System.out.println(mapper.getById(1));
13         } finally {
14             openSession.close();
15         }
16 
17     }

测试结果:

Employee [id=null, lastName=joy2x2, email=joy52112225@iclound.com, gender=女]

批量注册测试:

与上面的classy引入接口测试文件类似,全局文件mybatis-config.xml把 <mapper class="dao.EmployeeMapper"/> 换成 <package name="dao"/>即可;

全局文件mybatis-config.xml:

 1 <?xml version="1.0" encoding="UTF-8" ?>
 2 <!DOCTYPE configuration
 3   PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
 4   "http://mybatis.org/dtd/mybatis-3-config.dtd">
 5 <configuration>
 6 <properties resource="dbconfig.properties"></properties>
 7   <environments default="dev_mysql">
 8         <environment id="dev_mysql">
 9             <transactionManager type="JDBC"></transactionManager>
10             <dataSource type="POOLED">
11                 <property name="driver" value="${jdbc.driver}" />
12                 <property name="url" value="${jdbc.url}" />
13                 <property name="username" value="${jdbc.username}" />
14                 <property name="password" value="${jdbc.password}" />
15             </dataSource>
16         </environment>
17     
18         <environment id="dev_oracle">
19             <transactionManager type="JDBC" />
20             <dataSource type="POOLED">
21                 <property name="driver" value="${orcl.driver}" />
22                 <property name="url" value="${orcl.url}" />
23                 <property name="username" value="${orcl.username}" />
24                 <property name="password" value="${orcl.password}" />
25             </dataSource>
26         </environment>
27     </environments>
28   <!-- 将我们写好的SQL映射文件一定哟啊注册到全局配置文件中 -->
29   <mappers>
30       <package name="dao"/>
31   </mappers>
32 </configuration>
View Code

测试结果和上面的一样;

为了在视觉效果上 区分 src的dao中的 mapper接口和xml文件,可以在config文件目录(不是包 )中建立与mapper接口相同名称的包;因为编译后的文件,同包的文件在同一目录,不会区分src和config

 

posted @ 2022-02-09 11:54  啄木鸟伍迪  阅读(139)  评论(0编辑  收藏  举报
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