Merge pull request #481 from Emily-Jiang/revert-binary-incompatible-c…

…hanges

#431 - undo this change as it has binary incompatible changes

api/src/main/java/org/eclipse/microprofile/config/spi/ConfigSource.java

@@ -28,7 +28,6 @@
  *******************************************************************************/
 package org.eclipse.microprofile.config.spi;
 
-import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
 
@@ -82,21 +81,19 @@ public interface ConfigSource {
      * Return the properties in this config source
      * @return the map containing the properties in this config source
      */
-    default Map<String, String> getProperties() {
-        Map<String, String> props = new HashMap<>();
-        getPropertyNames().stream().forEach((prop) -> props.put(prop, getValue(prop)));
-        return props;
-    }
+    Map<String, String> getProperties();
 
     /**
-     * Gets all property names known to this config source, potentially without evaluating the values.
+     * Gets all property names known to this config source, without evaluating the values.
      *
      * For backwards compatibility, there is a default implementation that just returns the keys of {@code getProperties()}
      * slower ConfigSource implementations should replace this with a more performant implementation
      *
      * @return the set of property keys that are known to this ConfigSource
      */
-    Set<String> getPropertyNames();
+    default Set<String> getPropertyNames() {
+        return getProperties().keySet();
+    }
 
     /**
      * Return the ordinal for this config source. If a property is specified in multiple config sources, the value