Add support for strict property ordering (#2879)

Author: siy

src/main/java/com/fasterxml/jackson/databind/MapperFeature.java

@@ -375,6 +375,20 @@ public enum MapperFeature implements ConfigFeature
      */
     SORT_PROPERTIES_ALPHABETICALLY(false),
 
+    /**
+     * Feature that enforces strict ordering as requested by other configuration methods
+     * for POJO fields (note: does <b>not</b> apply to {@link java.util.Map}
+     * serialization!):
+     * if enabled, ordering is preserved even if {@link com.fasterxml.jackson.annotation.JsonCreator}
+     * is present. Without this feature properties referenced by {@link com.fasterxml.jackson.annotation.JsonCreator}
+     * taking precedence over other properties even if sorting is requested.
+     *<p>
+     * Note that if ordering is not enabled using other ways, this feature has no effect.
+     *<p>
+     * Feature is disabled by default.
+     */
+    STRICT_PROPERTIES_ORDERING(false),
+
     /*
     /******************************************************
     /* Name-related features

src/main/java/com/fasterxml/jackson/databind/cfg/MapperConfig.java

@@ -188,6 +188,14 @@ public final boolean shouldSortPropertiesAlphabetically() {
         return isEnabled(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY);
     }
 
+    /**
+     * Accessor for checking whether default settings for forcing property
+     * ordering is enabled.
+     */
+    public final boolean shouldPreservePropertiesOrdering() {
+        return isEnabled(MapperFeature.STRICT_PROPERTIES_ORDERING);
+    }
+
     /**
      * Accessor for checking whether configuration indicates that
      * "root wrapping" (use of an extra property/name pair at root level)

src/main/java/com/fasterxml/jackson/databind/introspect/POJOPropertiesCollector.java

@@ -1115,7 +1115,8 @@ protected void _sortProperties(Map<String, POJOPropertyBuilder> props)
         }
 
         // Third by sorting Creator properties before other unordered properties
-        if (_creatorProperties != null) {
+        // (unless strict ordering is requested)
+        if (_creatorProperties != null && !_config.shouldPreservePropertiesOrdering()) {
             /* As per [databind#311], this is bit delicate; but if alphabetic ordering
              * is mandated, at least ensure creator properties are in alphabetic
              * order. Related question of creator vs non-creator is punted for now,

src/test/java/com/fasterxml/jackson/databind/ObjectMapperTest.java

@@ -126,7 +126,7 @@ public void testCopy() throws Exception
         assertTrue(m.isEnabled(JsonParser.Feature.IGNORE_UNDEFINED));
 
         // // First: verify that handling of features is decoupled:
-        
+
         ObjectMapper m2 = m.copy();
         assertFalse(m2.isEnabled(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES));
         m2.enable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
@@ -215,7 +215,7 @@ public void testFailedCopy() throws Exception
         }
     }
 
-    public void testAnnotationIntrospectorCopyin() 
+    public void testAnnotationIntrospectorCopying()
     {
         ObjectMapper m = new ObjectMapper();
         m.setAnnotationIntrospector(new MyAnnotationIntrospector());
@@ -272,6 +272,32 @@ public void testConfigForPropertySorting() throws Exception
         assertTrue(dc.shouldSortPropertiesAlphabetically());
     }
 
+    // Test to ensure that we can check forced property ordering defaults...
+    public void testConfigForForcedPropertySorting() throws Exception
+    {
+        ObjectMapper m = new ObjectMapper();
+
+        // sort-alphabetically is disabled by default:
+        assertFalse(m.isEnabled(MapperFeature.STRICT_PROPERTIES_ORDERING));
+        SerializationConfig sc = m.getSerializationConfig();
+        assertFalse(sc.isEnabled(MapperFeature.STRICT_PROPERTIES_ORDERING));
+        assertFalse(sc.shouldPreservePropertiesOrdering());
+        DeserializationConfig dc = m.getDeserializationConfig();
+        assertFalse(dc.shouldPreservePropertiesOrdering());
+
+        // but when enabled, should be visible:
+        m = jsonMapperBuilder()
+                .enable(MapperFeature.STRICT_PROPERTIES_ORDERING)
+                .build();
+        sc = m.getSerializationConfig();
+        assertTrue(sc.isEnabled(MapperFeature.STRICT_PROPERTIES_ORDERING));
+        assertTrue(sc.shouldPreservePropertiesOrdering());
+        dc = m.getDeserializationConfig();
+        // and not just via SerializationConfig, but also via DeserializationConfig
+        assertTrue(dc.isEnabled(MapperFeature.STRICT_PROPERTIES_ORDERING));
+        assertTrue(dc.shouldPreservePropertiesOrdering());
+    }
+
     public void testJsonFactoryLinkage()
     {
         // first, implicit factory, giving implicit linkage
@@ -284,7 +310,7 @@ public void testJsonFactoryLinkage()
         assertSame(m, f.getCodec());
     }
 
-    public void testProviderConfig() throws Exception   
+    public void testProviderConfig() throws Exception
     {
         ObjectMapper m = new ObjectMapper();
         final String JSON = "{ \"x\" : 3 }";
@@ -332,7 +358,7 @@ public void testCustomDefaultPrettyPrinter() throws Exception
         assertEquals("[1,2]", m.writer().without(SerializationFeature.INDENT_OUTPUT)
                 .writeValueAsString(input));
     }
-    
+
     // For [databind#703], [databind#978]
     public void testNonSerializabilityOfObject()
     {

src/test/java/com/fasterxml/jackson/databind/ser/SerializationOrderTest.java

@@ -82,6 +82,22 @@ public BeanForGH311(@JsonProperty("b") int b, @JsonProperty("a") int a) { //b an
         public int getB() { return b; }
     }
 
+    static class BeanForStrictOrdering {
+        private final int a;
+        private int b;
+        private final int c;
+
+        @JsonCreator
+        public BeanForStrictOrdering(@JsonProperty("c") int c, @JsonProperty("a") int a) { //b and a are out of order, although alphabetic = true
+            this.a = a;
+            this.c = c;
+        }
+
+        public int getA() { return a; }
+        public int getB() { return b; }
+        public int getC() { return c; }
+    }
+
     // For [databind#2879]
     @JsonPropertyOrder({ "a", "c" })
     static class BeanFor2879 {
@@ -126,6 +142,11 @@ static class OrderingByIndexBean {
             .configure(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY, true)
             .build();
 
+    private final ObjectMapper STRICT_ALPHA_MAPPER = jsonMapperBuilder()
+            .enable(MapperFeature.SORT_PROPERTIES_ALPHABETICALLY)
+            .enable(MapperFeature.STRICT_PROPERTIES_ORDERING)
+            .build();
+
     public void testImplicitOrderByCreator() throws Exception {
         assertEquals("{\"c\":1,\"a\":2,\"b\":0}",
                 MAPPER.writeValueAsString(new BeanWithCreator(1, 2)));
@@ -187,4 +208,10 @@ public void testOrderByIndexEtc() throws Exception
         assertEquals(aposToQuotes("{'f':0,'u':0,'b':0,'a':0,'r':0}"),
                 ALPHA_MAPPER.writeValueAsString(new OrderingByIndexBean()));
     }
+
+    public void testStrictAlphaAndCreatorOrdering() throws Exception
+    {
+        String json = STRICT_ALPHA_MAPPER.writeValueAsString(new BeanForStrictOrdering(1, 2));
+        assertEquals("{\"a\":2,\"b\":0,\"c\":1}", json);
+    }
 }