Spring - Could not resolve placeholder error

Question

I'm new to Spring MVC & hibernate. I have configured an app using XML configuration and I want to use environment variables for JDBC connection options. While using Eclipse on Windows, I'm able to achieve this with the below

servlet.xml

<!-- Add support for Environment Variables -->
    <context:property-placeholder />

    <!-- Step 1: Define Database DataSource / connection pool -->
    <bean id="myDataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
          destroy-method="close">
        <property name="driverClass" value="com.mysql.cj.jdbc.Driver" />
        <property name="jdbcUrl" value="${JDBC_CONNECTION_STRING}" />
        <property name="user" value="${JDBC_UID}" />
        <property name="password" value="${JDBC_PWD}" /> 

When I try to deploy the WAR file to a remote tomcat server (on linux), I keep getting the below error

</pre><p><b>Root Cause</b></p><pre>java.lang.IllegalArgumentException: Could not resolve placeholder &#39;JDBC_CONNECTION_STRING&#39; in value &quot;${JDBC_CONNECTION_STRING}&quot;
        org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:178)
        org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:124)
        org.springframework.core.env.AbstractPropertyResolver.doResolvePlaceholders(AbstractPropertyResolver.java:239)
        org.springframework.core.env.AbstractPropertyResolver.resolveRequiredPlaceholders(AbstractPropertyResolver.java:210)
        org.springframework.context.support.PropertySourcesPlaceholderConfigurer.lambda$processProperties$0(PropertySourcesPlaceholderConfigurer.java:175)
        org.springframework.beans.factory.config.BeanDefinitionVisitor.resolveStringValue(BeanDefinitionVisitor.java:296)
        org.springframework.beans.factory.config.BeanDefinitionVisitor.resolveValue(BeanDefinitionVisitor.java:217)
        org.springframework.beans.factory.config.BeanDefinitionVisitor.visitPropertyValues(BeanDefinitionVisitor.java:147)
        org.springframework.beans.factory.config.BeanDefinitionVisitor.visitBeanDefinition(BeanDefinitionVisitor.java:85)
        org.springframework.beans.factory.config.PlaceholderConfigurerSupport.doProcessProperties(PlaceholderConfigurerSupport.java:225)
        org.springframework.context.support.PropertySourcesPlaceholderConfigurer.processProperties(PropertySourcesPlaceholderConfigurer.java:182)
        org.springframework.context.support.PropertySourcesPlaceholderConfigurer.postProcessBeanFactory(PropertySourcesPlaceholderConfigurer.java:157)
        org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:291)
        org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:167)
        org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:707)
        org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:533)
        org.springframework.web.servlet.FrameworkServlet.configureAndRefreshWebApplicationContext(FrameworkServlet.java:702)
        org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:668)
        org.springframework.web.servlet.FrameworkServlet.createWebApplicationContext(FrameworkServlet.java:716)
        org.springframework.web.servlet.FrameworkServlet.initWebApplicationContext(FrameworkServlet.java:591)
        org.springframework.web.servlet.FrameworkServlet.initServletBean(FrameworkServlet.java:530)
        org.springframework.web.servlet.HttpServletBean.init(HttpServletBean.java:170)
        javax.servlet.GenericServlet.init(GenericServlet.java:158)
        org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:543)
        org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
        org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
        org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
        org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:615)
        org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
        org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:818)
        org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1626)
        org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
        java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        java.lang.Thread.run(Thread.java:748)
</pre><p><b>Note</b> The full stack trace of the root cause is available in the server logs.</p><hr class="line" /><h3>Apache Tomcat/8.5.57</h3></body></html>

My remote server is a linux server and I have set environment variables in /etc/environment files. I have tried setting them using the export command as well and that made no difference. I have tried restarting tomcat, rebooting my server. However, nothing seems to get this to work.

Appreciate if I could get some help on how to resolve this issue.

• Aashish