Spring – PropertyPlaceholderConfigurer example

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


<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="org.apache.derby.jdbc.ClientDriver" />
<property name="url" value="jdbc:derby://localhost:1527/myeclipse" />
<property name="username" value="classiccars" />
<property name="password" value="classiccars" />
</bean>


In a corporate environment, the deployment detail is usually only can ‘touch’ by your system or database administrator, they just refuse to access your bean configuration file instead of request a new separate file for the deployment configuration.

In Spring, 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}.

To run the below example you need below jar files in your class path

• derbyclient.jar
• spring-dao.jar
• spring-jdbc.jar

ApplicationProperties.properties

Create a properties file (ApplicationProperties.properties) and include your deployment details, put it into your project class path.

jdbc.driverClassName=org.apache.derby.jdbc.ClientDriver

jdbc.url=jdbc:derby://localhost:1527/myeclipse

jdbc.username=classiccars

jdbc.password=classiccars

applicationContext.xml

Declare PropertyPlaceholderConfigurer in bean configuration file and map to the ‘ApplicationProperties.properties’ properties file you created just now.

<?xml version="1.0" encoding="UTF-8"?>

<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-2.0.xsd">

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

  <property name="location">

<value>ApplicationProperties.properties</value>

</property>

</bean>

<bean id="customerDAO" class="com.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>

SimpleJdbcCustomerDAO.java

package com;

import org.springframework.jdbc.datasource.DriverManagerDataSource;

public class SimpleJdbcCustomerDAO {

private DriverManagerDataSource dataSource;

/**

* @return the dataSource

*/

public DriverManagerDataSource getDataSource() {

return dataSource;

}

/**

* @param dataSource the dataSource to set

*/

public void setDataSource(DriverManagerDataSource dataSource) {

this.dataSource = dataSource;

}

}

Test.java

package com;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import org.springframework.jdbc.datasource.DriverManagerDataSource;

public class Test {

/**

* @param args

*/

public static void main(String[] args) {

// TODO Auto-generated method stub

ApplicationContext context = new ClassPathXmlApplicationContext("/applicationContext.xml");

SimpleJdbcCustomerDAO customerDao = (SimpleJdbcCustomerDAO)context.getBean("customerDAO");

DriverManagerDataSource dataSource = customerDao.getDataSource();

System.out.println("Driver Class Name :::  "+ dataSource.getDriverClassName());

System.out.println("Url :::  "+ dataSource.getUrl());

System.out.println("User Name :::  "+ dataSource.getUsername());

System.out.println("Password :::  "+ dataSource.getPassword());

}

}

Out Put

Driver Class Name :::  org.apache.derby.jdbc.ClientDriver

Url :::  jdbc:derby://localhost:1527/myeclipse

User Name :::  classiccars

Password :::  classiccars