Declare unified method for environment variable injection

diff --git a/modules/core/src/main/java/org/apache/synapse/config/xml/endpoints/DefaultEndpointFactory.java b/modules/core/src/main/java/org/apache/synapse/config/xml/endpoints/DefaultEndpointFactory.java
index 8b46106..157948f 100755
--- a/modules/core/src/main/java/org/apache/synapse/config/xml/endpoints/DefaultEndpointFactory.java
+++ b/modules/core/src/main/java/org/apache/synapse/config/xml/endpoints/DefaultEndpointFactory.java

@@ -165,5 +165,16 @@
                 }
             }
         }
-    }   
+    }
+
+    public String injectEnvironmentVariables (String parameter) {
+        String injectedValue = parameter;
+        if (parameter.contains(SynapseConstants.SYSTEM_VARIABLE_PREFIX)) {
+            String extractedEnvVariableKey = parameter.substring(parameter.lastIndexOf(":") + 1);
+            injectedValue = System.getenv(extractedEnvVariableKey);
+            log.debug("Environment variable " + extractedEnvVariableKey + " replaced with " +
+                    injectedValue);
+        }
+        return injectedValue;
+    }
 }