一、前言

mybatis-config.xml是MyBatis的核心配置文件，相信学过MyBatis的都有印象，至于它的由来不是我们这里关心的重点。如果想解读MyBatis的话，mybatis-config.xml这个配置文件是必须理解的，因为它贯穿于整个MyBatis核心模块的始终。

它的核心标签就是<configuration>，configuration下面就是它的子标签，就是一种树结构。如下图所示：

二、mybatis-config.xml的样例

1、样例1

<?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="org/mybatis/example/config.properties">
        <property name="username" value="dev_user"/>
        <property name="password" value="F2Fa3!33TYyg"/>
    </properties>

    <settings>
        <setting name="cacheEnabled" value="true"/>
        <setting name="lazyLoadingEnabled" value="true"/>
        <setting name="multipleResultSetsEnabled" value="true"/>
        <setting name="useColumnLabel" value="true"/>
        <setting name="useGeneratedKeys" value="false"/>
        <setting name="autoMappingBehavior" value="PARTIAL"/>
        <setting name="defaultExecutorType" value="SIMPLE"/>
        <setting name="defaultStatementTimeout" value="25"/>
        <setting name="safeRowBoundsEnabled" value="false"/>
        <setting name="mapUnderscoreToCamelCase" value="false"/>
        <setting name="localCacheScope" value="SESSION"/>
        <setting name="jdbcTypeForNull" value="OTHER"/>
        <setting name="lazyLoadTriggerMethods" value="equals,clone,hashCode,toString"/>
    </settings>
	
	<typeAliases>
	    <package name="ceam.pojo"/>
	</typeAliases>	
	
	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC"/>
			<dataSource type="POOLED">
			<property name="driver" value="${driver}"/>
			<property name="url" value="${url}"/>
			<property name="username" value="${username}"/>
			<property name="password" value="${password}"/>
			</dataSource>
		</environment>
	</environments>
	
	<mappers>
		<package name="ceam/dao"/>
	</mappers>
	
</configuration>

2、样例2

<?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="database.properties"></properties>
	
	<typeAliases>
	    <package name="ceam.pojo"/>
	</typeAliases>	
	
	<environments default="development">
		<environment id="development">
			<transactionManager type="JDBC"/>
			<dataSource type="POOLED">
			<property name="driver" value="${driver}"/>
			<property name="url" value="${url}"/>
			<property name="username" value="${username}"/>
			<property name="password" value="${password}"/>
			</dataSource>
		</environment>
	</environments>
	
	<mappers>
		<package name="ceam/dao"/>
	</mappers>
	
</configuration>

3、database.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/smbms?useUnicode=true&characterEncoding=utf-8
username=root
password=

它们都是放在如下目录中，然后经过加载器加载到classpath下。

关于更多的标签请看官方文档，今天先仔细看看，后面讲对它进行解析。