add systemPropertiesModeName example

spring-all/src/main/java/org/baeldung/properties/spring/PropertiesWithPlaceHolderConfigurer.java

@@ -0,0 +1,22 @@
+package org.baeldung.properties.spring;
+
+import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class PropertiesWithPlaceHolderConfigurer {
+
+    public PropertiesWithPlaceHolderConfigurer() {
+        super();
+    }
+
+
+    @Bean
+    public PropertyPlaceholderConfigurer propertyConfigurer() {
+        final PropertyPlaceholderConfigurer props = new PropertyPlaceholderConfigurer();
+        props.setSystemPropertiesMode(PropertyPlaceholderConfigurer.SYSTEM_PROPERTIES_MODE_FALLBACK);
+        return props;
+    }
+
+}