use LinkedHashMap for BasicDBObject since it maintains insertion order …

…JAVA-65

src/main/com/mongodb/BasicDBObject.java

@@ -30,7 +30,7 @@
  * obj.put( "foo", "bar" );
  * </pre></blockquote>
  */
-public class BasicDBObject extends HashMap<String,Object> implements DBObject {
+public class BasicDBObject extends LinkedHashMap<String,Object> implements DBObject {
 
     /**
      *  Creates an empty object.
@@ -52,29 +52,22 @@ public BasicDBObject(String key, Object value){
      * @param m map to convert
      */
     public BasicDBObject(Map m) {
-        Iterator<Map.Entry> i = m.entrySet().iterator();
-        while (i.hasNext()) {
-            Map.Entry entry = i.next();
-            put(entry.getKey().toString(), entry.getValue());
-        }
+        super(m);
     }
 
     /**
      * Converts a DBObject to a map.
      * @return the DBObject
      */
     public Map toMap() {
-        Map m = new HashMap();
-        m.putAll((HashMap)this);
-        return m;
+        return new LinkedHashMap<String,Object>(this);
     }
 
     /** Deletes a field from this object. 
      * @param key the field name to remove
      * @return the object removed
      */
     public Object removeField( String key ){
-        _keys.remove(key);
         return remove( key );
     }
 
@@ -86,7 +79,7 @@ public boolean isPartialObject(){
     }
 
     /** Checks if this object contains a given field
-     * @param field field name
+     * @param key field name
      * @return if the field exists
      */
     public boolean containsField( String field ){
@@ -157,7 +150,6 @@ public String getString( String key ){
      * @return the <code>val</code> parameter
      */
     public Object put( String key , Object val ){
-        _keys.add( key );
         return super.put( key , val );
     }
 
@@ -179,20 +171,11 @@ public void putAll( DBObject o ){
      * @return the <code>val</code> parameter
      */
     public BasicDBObject append( String key , Object val ){
-        _keys.add( key );
         put( key , val );
 
         return this;
     }
 
-    /** Gets a set of this object's fieldnames
-     * @return the fieldnames
-     */
-    public Set<String> keySet(){
-        assert( _keys.size() == size() );
-        return _keys;
-    }
-
     /** Returns a JSON serialization of this object
      * @return JSON serialization
      */    
@@ -211,10 +194,10 @@ public boolean equals( Object o ){
             return false;
 
         DBObject other = (DBObject)o;
-        if ( ! _keys.equals( other.keySet() ) )
+        if ( ! keySet().equals( other.keySet() ) )
             return false;
 
-        for ( String key : _keys ){
+        for ( String key : keySet() ){
             Object a = get( key );
             Object b = other.get( key );
 
@@ -231,6 +214,5 @@ public boolean equals( Object o ){
         return true;
     }
 
-    private final Set<String> _keys = new OrderedSet<String>();
     private boolean _isPartialObject = false;
 }

src/test/com/mongodb/DBObjectTest.java

@@ -19,6 +19,7 @@
 import java.net.*;
 import java.util.*;
 
+
 import org.testng.annotations.Test;
 
 import com.mongodb.util.*;
@@ -153,6 +154,24 @@ public void testInnerDot() {
         assertTrue(thrown);
     }
 
+    @Test(groups = {"basic"})
+    public void testEntrySetOrder() {
+        final List<String> expectedKeys = new ArrayList<String>();
+        final BasicDBObject o = new BasicDBObject();
+        for (int i = 1; i < 1000; i++) {
+            final String key = String.valueOf(i);
+            expectedKeys.add(key);
+            o.put(key, "Test" + key);
+        }
+        final List<String> keysFromKeySet = new ArrayList<String>(o.keySet());
+        final List<String> keysFromEntrySet = new ArrayList<String>();
+        for (final Map.Entry<String, Object> entry : o.entrySet()) {
+            keysFromEntrySet.add(entry.getKey());
+        }
+        assertEquals(keysFromKeySet, expectedKeys);
+        assertEquals(keysFromEntrySet, expectedKeys);
+    }
+
     private DB _db;
 
     public static void main( String args[] ) {