Added more utility methods to Settings

- names() to return the direct settings names
- getAsSettings(String) to return the settings mapped to the given name (like getByPrefix(...) except no need to provide a tailing '.')

src/main/java/org/elasticsearch/common/settings/ImmutableSettings.java

@@ -218,6 +218,11 @@ public class ImmutableSettings implements Settings {
         return builder.build();
     }
 
+    @Override
+    public Settings getAsSettings(String setting) {
+        return getByPrefix(setting + ".");
+    }
+
     @Override
     public String get(String setting) {
         String retVal = settings.get(setting);
@@ -563,6 +568,20 @@ public class ImmutableSettings implements Settings {
         }
     }
 
+    @Override
+    public Set<String> names() {
+        Set<String> names = new HashSet<>();
+        for (String key : settings.keySet()) {
+            int i = key.indexOf(".");
+            if (i < 0) {
+                names.add(key);
+            } else {
+                names.add(key.substring(0, i));
+            }
+        }
+        return names;
+    }
+
     @Override
     public String toDelimitedString(char delimiter) {
         StringBuilder sb = new StringBuilder();

src/main/java/org/elasticsearch/common/settings/Settings.java

@@ -29,6 +29,7 @@ import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.ToXContent;
 
 import java.util.Map;
+import java.util.Set;
 
 /**
  * Immutable settings allowing to control the configuration.
@@ -58,6 +59,11 @@ public interface Settings extends ToXContent {
      */
     Settings getByPrefix(String prefix);
 
+    /**
+     * Returns the settings mapped to the given setting name.
+     */
+    Settings getAsSettings(String setting);
+
     /**
      * The class loader associated with this settings, or {@link org.elasticsearch.common.Classes#getDefaultClassLoader()}
      * if not set.
@@ -312,6 +318,11 @@ public interface Settings extends ToXContent {
      */
     Version getAsVersion(String setting, Version defaultVersion) throws SettingsException;
 
+    /**
+     * @return  The direct keys of this settings
+     */
+    Set<String> names();
+
     /**
      * Returns the settings as delimited string.
      */

src/test/java/org/elasticsearch/common/settings/ImmutableSettingsTests.java

@@ -27,6 +27,7 @@ import org.junit.Test;
 
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import static org.elasticsearch.common.settings.ImmutableSettings.settingsBuilder;
 import static org.hamcrest.Matchers.*;
@@ -184,4 +185,37 @@ public class ImmutableSettingsTests extends ElasticsearchTestCase {
                 Matchers.<String, Object>hasEntry("foo.bar", "def"),
                 Matchers.<String, Object>hasEntry("foo.baz", "ghi")));
     }
+
+    @Test
+    public void testGetAsSettings() {
+        Settings settings = settingsBuilder()
+                .put("foo", "abc")
+                .put("foo.bar", "def")
+                .put("foo.baz", "ghi").build();
+
+        Settings fooSettings = settings.getAsSettings("foo");
+        assertThat(fooSettings.get("bar"), equalTo("def"));
+        assertThat(fooSettings.get("baz"), equalTo("ghi"));
+    }
+
+    @Test
+    public void testNames() {
+        Settings settings = settingsBuilder()
+                .put("bar", "baz")
+                .put("foo", "abc")
+                .put("foo.bar", "def")
+                .put("foo.baz", "ghi").build();
+
+        Set<String> names = settings.names();
+        assertThat(names.size(), equalTo(2));
+        assertTrue(names.contains("bar"));
+        assertTrue(names.contains("foo"));
+
+        Settings fooSettings = settings.getAsSettings("foo");
+        names = fooSettings.names();
+        assertThat(names.size(), equalTo(2));
+        assertTrue(names.contains("bar"));
+        assertTrue(names.contains("baz"));
+
+    }
 }