Maintain order when using inline maps and lists

src/main/java/org/mvel2/ast/InlineCollectionNode.java

@@ -28,8 +28,8 @@
 import org.mvel2.util.CollectionParser;
 
 import java.lang.reflect.Array;
-import java.util.ArrayList;
-import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 
@@ -123,7 +123,7 @@ private void parseGraph(boolean compile, Class type, ParserContext pCtx) {
 
   private Object execGraph(Object o, Class type, Object ctx, VariableResolverFactory factory) {
     if (o instanceof List) {
-      ArrayList list = new ArrayList(((List) o).size());
+      LinkedList list = new LinkedList();
 
       for (Object item : (List) o) {
         list.add(execGraph(item, type, ctx, factory));
@@ -132,7 +132,7 @@ private Object execGraph(Object o, Class type, Object ctx, VariableResolverFacto
       return list;
     }
     else if (o instanceof Map) {
-      HashMap map = new HashMap();
+      LinkedHashMap map = new LinkedHashMap();
 
       for (Object item : ((Map) o).keySet()) {
         map.put(execGraph(item, type, ctx, factory), execGraph(((Map) o).get(item), type, ctx, factory));

src/main/java/org/mvel2/util/CollectionParser.java

@@ -23,10 +23,7 @@
 import org.mvel2.ParserContext;
 import org.mvel2.compiler.ExecutableStatement;
 
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 
 import static org.mvel2.util.ParseTools.*;
 
@@ -94,7 +91,7 @@ public Object parseCollection(char[] property, int start, int offset, boolean su
 
   private Object parseCollection(boolean subcompile) {
     if (end - start == 0) {
-      if (type == LIST) return new ArrayList();
+      if (type == LIST) return new LinkedList();
       else return EMPTY_ARRAY;
     }
 
@@ -107,10 +104,10 @@ private Object parseCollection(boolean subcompile) {
       switch (type) {
         case ARRAY:
         case LIST:
-          list = new ArrayList<Object>();
+          list = new LinkedList<Object>();
           break;
         case MAP:
-          map = new HashMap<Object, Object>();
+          map = new LinkedHashMap<Object, Object>();
           break;
       }
     }
@@ -188,7 +185,7 @@ else if (cursor < end) {
 
         case ':':
           if (type != MAP) {
-            map = new HashMap<Object, Object>();
+            map = new LinkedHashMap<Object, Object>();
             type = MAP;
           }
           curr = createStringTrimmed(property, st, cursor - st);

src/test/java/org/mvel2/tests/core/InlineCollectionsTests.java

@@ -13,6 +13,8 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
+import java.util.LinkedHashSet;
 
 public class InlineCollectionsTests extends AbstractTest {
   public void testListCreation2() {
@@ -360,4 +362,40 @@ public void testElementToList() {
   }
 
 
+    public void testInlineCollectionOrderOfKeys() {
+
+        Set<String> keys = new LinkedHashSet<String>();
+        keys.add("a");
+        keys.add("b");
+        keys.add("c");
+        keys.add("d");
+        keys.add("e");
+
+        String mvelSource = "[ 'a' : 1, 'b' : 2, 'c' : 3, 'd' : 4, 'e' : 5 ]";
+        Map eval = (Map) MVEL.eval(mvelSource);
+
+        assertTrue(hasSameOrder(keys, eval.keySet()));
+    }
+
+    private Boolean hasSameOrder(Set<String> a, Set<String> b) {
+
+        // Check if they have same values
+        if (!a.equals(b)) {
+            return false;
+        }
+
+        String[] aArray = a.toArray(new String[a.size()]);
+        String[] bArray = b.toArray(new String[b.size()]);
+
+        // Check keys to make sure order is the same
+        for (int i=0; i < aArray.length; i ++) {
+            if (!aArray[i].equals(bArray[i])) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+
 }