利用Spring的propertyConfigurer類讀取.property數據庫配置文件

1.Spring的框架中，org.springframework.beans.factory.config.PropertyPlaceholderConfigurer類可以將.properties(key/value形式)文件中一些動態設定的值(value)，在XML中替換爲佔位該鍵($key$)的值，.properties文件可以根據客戶需求，自定義一些相關的參數，這樣的設計可提供程序的靈活性。

2.在Spring中，使用PropertyPlaceholderConfigurer可以在XML配置文件中加入外部屬性文件，當然也可以指定外部文件的編碼，如：
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="location">
      <value>conf/sqlmap/jdbc.properties</value>
    </property>
     <property name="fileEncoding">
       <value>UTF-8</value>
     </property>
</bean>
當然也可以引入多個屬性文件，如：
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
   <property name="locations">
    <list>
     <value>/WEB-INF/mail.properties</value>
     <value>classpath: conf/sqlmap/jdbc.properties</value>//注意這兩種value值的寫法
    </list>
   </property>
</bean>

基本的使用方法是：

Xml代碼
<bean id="propertyConfigurerForAnalysis" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="location">
        <value>classpath:/spring/include/dbQuery.properties</value>
    </property>
    <property name="fileEncoding">
       <value>UTF-8</value>
     </property>

</bean>

其中classpath是引用src目錄下的文件寫法。

當存在多個Properties文件時，配置就需使用locations了：

Xml代碼
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="locations">
       <list>
          <value>classpath:/spring/include/jdbc-parms.properties</value>
          <value>classpath:/spring/include/base-config.properties</value>
          <value>classpath*:config/jdbc.properties</value>
        </list>
    </property>
</bean>

接下來我們要使用多個PropertyPlaceholderConfigurer來分散配置，達到整合多工程下的多個分散的Properties文件，其配置如下
Xml代碼

<bean id="propertyConfigurerForProject1" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="order" value="1" />
    <property name="ignoreUnresolvablePlaceholders" value="true" />
    <property name="location">
       <value>classpath:/spring/include/dbQuery.properties</value>
    </property>
</bean>

Xml代碼

<bean id="propertyConfigurerForProject2" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="order" value="2" />
    <property name="ignoreUnresolvablePlaceholders" value="true" />
    <property name="locations">
      <list>
        <value>classpath:/spring/include/jdbc-parms.properties</value>
        <value>classpath:/spring/include/base-config.properties</value>
      </list>
    </property>
</bean> 其中order屬性代表其加載順序，而ignoreUnresolvablePlaceholders爲是否忽略不可解析的Placeholder，如配置了多個PropertyPlaceholderConfigurer，則需設置爲true

3.譬如，jdbc.properties的內容爲：
jdbc.driverClassName=com.MySQL.jdbc.Driver
jdbc.url=jdbc:mysql://localhost/mysqldb?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=round;
jdbc.username=root
jdbc.password=123456

4.那麼在spring配置文件中，我們就可以這樣寫：
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
   <property name="locations">
    <list>
     <value>classpath: conf/sqlmap/jdbc.properties </value>
    </list>
   </property>
</bean>

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
   <property name="driverClassName" value="${jdbc.driverClassName}" />
   <property name="url" value="${jdbc.url}" />
   <property name="username" value="${jdbc.username}" />
   <property name="password" value="${jdbc.password}" />
</bean>

5.這樣，一個簡單的數據源就設置完畢了。可以看出：PropertyPlaceholderConfigurer起的作用就是將佔位符指向的數據庫配置信息放在bean中定義的工具。

Java代碼

<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName"
value="${jdbc.driverClassName}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</bean>
<bean id="sessionFactory"
class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="mappingResources">
<list>
<value>cn/xg/hibernate/spring/User.hbm.xml</value>
<value>cn/xg/hibernate/spring/Group.hbm.xml</value>
</list>
<!-- 加載一個路徑下的*.hbm.xml文件方法:
<property name="mappingDirectoryLocations">
<list>
<value>classpath:/cn/xg/spring/model</value>
</list>
</property>
-->
</property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">
${hibernate.dialect}
</prop>
<prop key="hibernate.show_sql">true</prop>
</props>
</property>
</bean>
<bean id="userMgrImpl" class="cn.xg.hibernate.spring.UserMgrImpl">
<property name="sessionFactory" ref="sessionFactory" />
</bean>
<bean id="groupMgrImpl"
class="cn.xg.hibernate.spring.GroupMgrImpl">
<property name="sessionFactory" ref="sessionFactory" />
<property name="userImpl" ref="userMgrImpl"/>
<property name="transactionTemplate" ref="transactionTemplate"/>
</bean>
<bean id="transactionManager"
class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory" />
</bean>
<bean id="transactionTemplate" class="org.springframework.transaction.support.TransactionTemplate">
<property name="transactionManager" ref="transactionManager"/>
</bean>
<!--
<bean id="groupMgr"
class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<property name="transactionManager" ref="transactionManager" />
<property name="target" ref="groupMgrImpl" />
<property name="transactionAttributes">
<props>
<prop key="add*">PROPAGATION_REQUIRED</prop>
<prop key="get*">PROPAGATION_REQUIRED</prop>
<prop key="*">readOnly</prop>
</props>
</property>
</bean>
-->
<!-- 事務的傳播特性
<tx:advice id="txAdvice">
<tx:attributes>
<tx:method name="add*" propagation="REQUIRED" />
<tx:method name="get*" propagation="REQUIRED" />
<tx:method name="*" read-only="true" />
</tx:attributes>
</tx:advice>
<aop:config>
<aop:advisor pointcut="execution(* cn.xg.hibernate.spring.*.*(..))"
advice-ref="txAdvice" />
</aop:config>
-->
</beans>
jdbc.properties
jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/數據庫名
jdbc.username=數據庫用戶名
jdbc.password=數據庫密碼
hibernate.dialect=org.hibernate.dialect.MySQLDialect(方言.這裏是MySql)