How to connect OS environment variables to placeholders in application.properties in a Spring Web app project?

Question

1) I created environment file as mentioned here

• I created a file called Prod.env and entered following

  SPRING_DATASOURCE_URL="jdbc:mysql://5.6.7.8:3306/ab?autoReconnect=true&characterEncoding=utf8"
  SPRING_DATASOURCE_USERNAME="root"
  SPRING_DATASOURCE_PASSWORD="IWin"
  

• And then I executed this command export $(cat Prod.env | xargs)

2) Then I created application.properties under WEB-INF with following code

spring.datasource.driver-class-name:com.mysql.jdbc.Driver
spring.datasource.url=${SPRING_DATASOURCE_URL}
spring.datasource.username=${SPRING_DATASOURCE_USERNAME}
spring.datasource.password=${SPRING_DATASOURCE_PASSWORD}

3) Then in spring-security.xml

  <b:bean id="mappings" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <b:property name="location">
            <b:value>/WEB-INF/application.properties</b:value>
        </b:property>
  </b:bean> 
  <b:bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
        destroy-method="close">
        <b:property name="driverClassName" value="com.mysql.jdbc.Driver" /> 
        <b:property name="url" value="${spring.datasource.url}" />
        <b:property name="username" value="${spring.datasource.username}" />
        <b:property name="password" value="${spring.datasource.password}" />
  </b:bean>

Now, when I save everything and restart I get

SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
org.springframework.beans.factory.BeanDefinitionStoreException: Invalid bean definition with name 'dataSource' defined in ServletContext resource [/WEB-INF/spring/appServlet/spring-security.xml]: Could not resolve placeholder 'SPRING_DATASOURCE_URL' in string value "jdbc:mysql:${SPRING_DATASOURCE_URL}"; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'SPRING_DATASOURCE_URL' in string value "jdbc:mysql:${SPRING_DATASOURCE_URL}"

What I'm trying to achieve is: Access an environment variable via application.properties (or doing some configuration in spring-security.xml ) , but not with java code. What am I missing here?

I have searched several questions, but none explains it clearly. Please help

Note: Mine is not a spring boot project. It is normal Spring 4.0.3 web app.

Answer 1

The normal approach is that the application should not know anything about the environment type (ENV, INTP, PROD, etc.).It means, do not specify environment (stage) name, but use the same name of properties file, an put needed version of the file into the classpath. For instance, on DEV environment you put to the classpath the DEV version of application.properties, on PROD environment you put to the classpath the PROD version of application.properties.

In your case I'd suggest that you remove application.properties from WEB-INF and put it outside of WAR (if you use EAR, also outside of EAR). Put it to the classpath of your application or classpath of application server, and configure your bean as follows:

  <b:bean id="mappings" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <b:property name="location">
            <b:value>classpath*:application.properties</b:value>
        </b:property>
  </b:bean> 

Property spring.datasource.driver-class-name it is not needed in the properties file, because you have already defined it in XML directly:

<b:property name="driverClassName" value="com.mysql.jdbc.Driver" /> 

Other properties you can define in application.properties as follows:

spring.datasource.url="jdbc:mysql://5.6.7.8:3306/ab?autoReconnect=true&characterEncoding=utf8"
spring.datasource.username=root
spring.datasource.password=IWin

Put application.properties not into WAR, but to the classpath of your app server.