FELIX-6736 Emit properties in alphabetical order

cm.json/src/main/java/org/apache/felix/cm/json/io/impl/ConfigurationWriterImpl.java

@@ -21,11 +21,14 @@
 import java.io.FilterWriter;
 import java.io.IOException;
 import java.io.Writer;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.Dictionary;
 import java.util.Enumeration;
 import java.util.Hashtable;
 import java.util.Map;
+import java.util.SortedSet;
+import java.util.TreeSet;
 
 import org.apache.felix.cm.json.io.ConfigurationResource;
 import org.apache.felix.cm.json.io.ConfigurationWriter;
@@ -85,9 +88,24 @@ public void writeConfiguration(final Dictionary<String, Object> properties) thro
         }
     }
 
+    /**
+     * Returns an alphabetically sorted enumeration of the given enumeration.
+     *
+     * @param enumeration the enumeration to sort
+     * @return the sorted enumeration
+     */
+    private static Enumeration<String> sortedEnumeration(Enumeration<String> enumeration) {
+        SortedSet<String> sortedSet = new TreeSet<>();
+        while (enumeration.hasMoreElements())
+        {
+            sortedSet.add(enumeration.nextElement());
+        }
+        return Collections.enumeration(sortedSet);
+    }
+
     private void writeConfigurationInternal(final Dictionary<String, Object> properties) throws IOException {
         generator.writeStartObject();
-        final Enumeration<String> e = properties.keys();
+        final Enumeration<String> e = sortedEnumeration(properties.keys());
         while (e.hasMoreElements()) {
             final String name = e.nextElement();
             final Object value = properties.get(name);

cm.json/src/main/java/org/apache/felix/cm/json/io/package-info.java

@@ -16,7 +16,7 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-@Version("1.0.0")
+@Version("1.1.0")
 package org.apache.felix.cm.json.io;
 
 import org.osgi.annotation.versioning.Version;

cm.json/src/test/java/org/apache/felix/cm/json/io/impl/ConfigurationWriterImplTest.java

@@ -0,0 +1,47 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.felix.cm.json.io.impl;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.io.StringWriter;
+import java.util.Dictionary;
+
+import org.junit.Test;
+
+public class ConfigurationWriterImplTest {
+
+    @Test
+    public void testWriteInAlphabeticalOrder() throws IOException {
+        final ConfigurationWriterImpl cfgWriter = new ConfigurationWriterImpl();
+        StringWriter writer = new StringWriter();
+        Dictionary<String, Object> properties = new OrderedDictionary();
+        properties.put("Z", "Z");
+        properties.put("A", Integer.valueOf(1));
+        properties.put("b", Long.valueOf(2000l));
+        cfgWriter.build(writer).writeConfiguration(properties);
+        assertEquals("{\n"
+                + "  \"A:Integer\":1,\n"
+                + "  \"Z\":\"Z\",\n"
+                + "  \"b\":2000\n"
+                + "}", writer.toString());
+    }
+
+}