add Config.entrySet() which returns the set of paths and non-null values

config/src/main/java/com/typesafe/config/Config.java

@@ -4,6 +4,8 @@
 package com.typesafe.config;
 
 import java.util.List;
+import java.util.Map;
+import java.util.Set;
 
 /**
  * An immutable map from config paths to config values.
@@ -54,10 +56,11 @@ import java.util.List;
  * are performed for you though.
  *
  * <p>
- * If you want to iterate over the contents of a {@code Config}, you have to get
- * its {@code ConfigObject} with {@link #root()}, and then iterate over the
- * {@code ConfigObject}.
- *
+ * If you want to iterate over the contents of a {@code Config}, you can get its
+ * {@code ConfigObject} with {@link #root()}, and then iterate over the
+ * {@code ConfigObject} (which implements <code>java.util.Map</code>). Or, you
+ * can use {@link #entrySet()} which recurses the object tree for you and builds
+ * up a <code>Set</code> of all path-value pairs where the value is not null.
  *
  * <p>
  * <em>Do not implement {@code Config}</em>; it should only be implemented by
@@ -256,6 +259,17 @@ public interface Config extends ConfigMergeable {
      */
     boolean isEmpty();
 
+    /**
+     * Returns the set of path-value pairs, excluding any null values, found by
+     * recursing {@link #root() the root object}. Note that this is very
+     * different from <code>root().entrySet()</code> which returns the set of
+     * immediate-child keys in the root object and includes null values.
+     * 
+     * @return set of paths with non-null values, built up by recursing the
+     *         entire tree of {@link ConfigObject}
+     */
+    Set<Map.Entry<String, ConfigValue>> entrySet();
+
     /**
      *
      * @param path

config/src/main/java/com/typesafe/config/impl/SimpleConfig.java

@@ -3,10 +3,13 @@
  */
 package com.typesafe.config.impl;
 
+import java.util.AbstractMap;
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.TimeUnit;
 
 import com.typesafe.config.Config;
@@ -20,12 +23,10 @@ import com.typesafe.config.ConfigValue;
 import com.typesafe.config.ConfigValueType;
 
 /**
- * One thing to keep in mind in the future: if any Collection-like APIs are
- * added here, including iterators or size() or anything, then we'd have to
- * grapple with whether ConfigNull values are "in" the Config (probably not) and
- * we'd probably want to make the collection look flat - not like a tree. So the
- * key-value pairs would be all the tree's leaf values, in a big flat list with
- * their full paths.
+ * One thing to keep in mind in the future: as Collection-like APIs are added
+ * here, including iterators or size() or anything, they should be consistent
+ * with a one-level java.util.Map from paths to non-null values. Null values are
+ * not "in" the map.
  */
 final class SimpleConfig implements Config, MergeableValue {
 
@@ -73,6 +74,31 @@ final class SimpleConfig implements Config, MergeableValue {
         return object.isEmpty();
     }
 
+    private static void findPaths(Set<Map.Entry<String, ConfigValue>> entries, Path parent,
+            AbstractConfigObject obj) {
+        for (Map.Entry<String, ConfigValue> entry : obj.entrySet()) {
+            String elem = entry.getKey();
+            ConfigValue v = entry.getValue();
+            Path path = Path.newKey(elem);
+            if (parent != null)
+                path = path.prepend(parent);
+            if (v instanceof AbstractConfigObject) {
+                findPaths(entries, path, (AbstractConfigObject) v);
+            } else if (v instanceof ConfigNull) {
+                // nothing; nulls are conceptually not in a Config
+            } else {
+                entries.add(new AbstractMap.SimpleImmutableEntry<String, ConfigValue>(path.render(), v));
+            }
+        }
+    }
+
+    @Override
+    public Set<Map.Entry<String, ConfigValue>> entrySet() {
+        Set<Map.Entry<String, ConfigValue>> entries = new HashSet<Map.Entry<String, ConfigValue>>();
+        findPaths(entries, null, object);
+        return entries;
+    }
+
     static private AbstractConfigValue find(AbstractConfigObject self,
             String pathExpression, ConfigValueType expected, String originalPath) {
         Path path = Path.newPath(pathExpression);

config/src/test/scala/com/typesafe/config/impl/ConfigTest.scala

@@ -782,6 +782,16 @@ class ConfigTest extends TestUtils {
         assertEquals(-1, o3.lineNumber)
     }
 
+    @Test
+    def test01EntrySet() {
+        val conf = ConfigFactory.load("test01")
+
+        val javaEntries = conf.entrySet()
+        val entries = Map((javaEntries.asScala.toSeq map { e => (e.getKey(), e.getValue()) }): _*)
+        assertEquals(Some(intValue(42)), entries.get("ints.fortyTwo"))
+        assertEquals(None, entries.get("nulls.null"))
+    }
+
     @Test
     def test02SubstitutionsWithWeirdPaths() {
         val conf = ConfigFactory.load("test02")