spring配置文件中的使用

context:property-placeholder方便了我们数据库的配置。

spring 3.0 后提供了 注解配置引入,<context:property-placeholder/>,方便。但是往往第一次使用时会遇到此属性配置进applicationContext.xml文件中,会出现红叉:
“The prefix "context" for element "context:property-placeholder" is not bound. ”

只需要在文件头中引入:xmlns:context="http://www.springframework.org/schema/context" 即可。
举例如下:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

   <context:property-placeholder location="classpath:jdbc.properties"/>
   <bean id="dataSource"
        class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
    <property name="driverClass" value="${jdbc.driverClassName}"/>
    <property name="jdbcUrl" value="${jdbc.url}"/>
    <property name="user" value="${jdbc.username}"/>
    <property name="password" value="${jdbc.password}"/>
   </bean>
</beans>

jdbc.properties:
#jdbc配置
jdbc.driverClassName = oracle.jdbc.driver.OracleDriver
jdbc.url = jdbc:oracle:thin:@//localhost:1521/orcl
jdbc.username = scotter
jdbc.password = 123


另外需要注意的是,如果遇到下面着着这种问题:

A模块和B模块都分别拥有自己的Spring XML配置,并分别拥有自己的配置文件:

A模块的Spring配置文件如下:

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  1. <?xml version="1.0" encoding="UTF-8" ?>  
  2. <beans xmlns="http://www.springframework.org/schema/beans"  
  3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
  4.        xmlns:context="http://www.springframework.org/schema/context"  
  5.        xmlns:p="http://www.springframework.org/schema/p"  
  6.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd  
  7.        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd">  
  8.    <context:property-placeholder location="classpath*:conf/conf_a.properties"/>  
  9.    <bean class="com.xxx.aaa.Bean1"  
  10.           p:driverClassName="${modulea.jdbc.driverClassName}"  
  11.           p:url="${modulea.jdbc.url}"  
  12.           p:username="${modulea.jdbc.username}"  
  13.           p:password="${modulea.jdbc.password}"/>  
  14. </beans>  
conf/conf_a.properties:
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  1. modulea.jdbc.driverClassName=com.mysql.jdbc.Driver  
  2. modulea.jdbc.username=cartan  
  3. modulea.jdbc.password=superman  
  4. modulea.jdbc.url=jdbc:mysql://127.0.0.1:3306/modulea?useUnicode=true&characterEncoding=utf8  


B模块的Spring配置文件如下:
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  1. <?xml version="1.0" encoding="UTF-8" ?>    
  2. <beans xmlns="http://www.springframework.org/schema/beans"    
  3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    
  4.        xmlns:context="http://www.springframework.org/schema/context"    
  5.        xmlns:p="http://www.springframework.org/schema/p"    
  6.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd    
  7.        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd">    
  8.    <context:property-placeholder location="classpath*:conf/conf_b.properties"/>    
  9.    <bean class="com.xxx.bbb.Bean1"    
  10.           p:driverClassName="${moduleb.jdbc.driverClassName}"    
  11.           p:url="${moduleb.jdbc.url}"    
  12.           p:username="${moduleb.jdbc.username}"    
  13.           p:password="${moduleb.jdbc.password}"/>    
  14. </beans>    
conf/conf_b.properties:
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  1. moduleb.jdbc.driverClassName=com.mysql.jdbc.Driver  
  2. moduleb.jdbc.username=cartan  
  3. moduleb.jdbc.password=superman  
  4. moduleb.jdbc.url=jdbc:mysql://127.0.0.1:3306/modulea?useUnicode=true&characterEncoding=utf8  

spring容器中最多 单独运行A模块,或单独运行B模块都是正常的,但将A和B两个模块集成后运行,Spring容器就启动不了了: Could not resolve placeholder 'moduleb.jdbc.driverClassName' in string value "${moduleb.jdbc.driverClassName}"

原因:Spring容器采用反射扫描的发现机制,在探测到Spring容器中有一个org.springframework.beans.factory.config.PropertyPlaceholderConfigurer的Bean就会停止对剩余PropertyPlaceholderConfigurer的扫描只能定义一个context:property-placeholder,不然就出现那种个错误,那如何来解决上面的问题呢?

A和B模块去掉

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  1. <context:property-placeholder location="classpath*:conf/conf_b.properties"/>   

然后重新写个xml:

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  1. <?xml version="1.0" encoding="UTF-8" ?>  
  2. <beans xmlns="http://www.springframework.org/schema/beans"  
  3.        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
  4.        xmlns:context="http://www.springframework.org/schema/context"  
  5.        xmlns:p="http://www.springframework.org/schema/p"  
  6.        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd  
  7.        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd">  
  8.    <context:property-placeholder location="classpath*:conf/conf*.properties"/>  
  9.    <import resource="a.xml"/>  
  10.    <import resource="b.xml"/>  
  11. </beans>  

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