Spring PropertyPlaceholderConfigurer example

Often times, most Spring developers just put the entire deployment details (database details, log file path) in XML bean configuration file as following :

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"> 
<bean id="customerDAO" class="com.mkyong.customer.dao.impl.JdbcCustomerDAO">

<property name="dataSource" ref="dataSource" />
</bean>

<bean id="customerSimpleDAO" class="com.mkyong.customer.dao.impl.SimpleJdbcCustomerDAO">

<property name="dataSource" ref="dataSource" />
</bean>

<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">

<property name="driverClassName" value="com.mysql.jdbc.Driver" />
<property name="url" value="jdbc:mysql://localhost:3306/mkyongjava" />
<property name="username" value="root" />
<property name="password" value="password" />
</bean>

</beans>

But, in a corporate environment, deployment detail is usually only can ‘touch’ by your system or database administrator, they just refuse to access your bean configuration file directly, and they will request a separate file for deployment configuration, for example, a simple properties, with deployment detail only.

PropertyPlaceholderConfigurer

example

To fix it, you can use

PropertyPlaceholderConfigurer

class to externalize the deployment details into a properties file, and access from bean configuration file via a special format –

${variable}

.

Create a properties file (

database.properties

), include your database details, put it into your project class path.

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mkyongjava
jdbc.username=root
jdbc.password=password

Declare a

PropertyPlaceholderConfigurer

in bean configuration file and map to the ‘

database.properties

‘ properties file you created just now.

<bean
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">

<property name="location">
<value>database.properties</value>
</property>
</bean>

Full example

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd"> 
<bean
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">

<property name="location">
<value>database.properties</value>
</property>
</bean>

<bean id="customerDAO" class="com.mkyong.customer.dao.impl.JdbcCustomerDAO">

<property name="dataSource" ref="dataSource" />
</bean>

<bean id="customerSimpleDAO"
class="com.mkyong.customer.dao.impl.SimpleJdbcCustomerDAO">

<property name="dataSource" ref="dataSource" />
</bean>

<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>

</beans>

Alternative usage

You also can use

PropertyPlaceholderConfigurer

to share some constant variables to all other beans. For example, define your log file location in a properties file, and access the properties value from different beans configuration files via

${log.filepath}

.