Fix #3070: change SerializationFeature.FAIL_ON_EMPTY_BEANS default to false (#4817)

Author: cowtowncoder

release-notes/VERSION

@@ -55,6 +55,7 @@ Versions: 3.x (for earlier see VERSION-2.x)
 #3044: Rename `JsonDeserializer`/`JsonSerializer` as `ValueDeserializer`/`ValueSerializer`
 #3046: Rename `JsonSerializable` as `JacksonSerializable`
 #3047: Rename `Bean[De]SerializerModifier` as `Value[De]SerializerModifier`
+#3070: Change default for `SerializationFeature.FAIL_ON_EMPTY_BEANS` to `false`
 #3536: Create new exception type `JsonNodeException` for use by `JsonNode`-related problems
 #3542: Rename "com.fasterxml.jackson" -> "tools.jackson"
 #3601: Change `Optional` deserialization from "absent" value into `null`, from "empty"

src/main/java/tools/jackson/databind/DeserializationFeature.java

@@ -363,8 +363,7 @@ public enum DeserializationFeature implements ConfigFeature
 
     /**
      * Feature that can be enabled to allow empty JSON Array
-     * value (that is, <code>[ ]</code>) to be bound to POJOs (and
-     * with 2.9, other values too) as `null`.
+     * value (that is, <code>[ ]</code>) to be bound to POJOs as `null`.
      * If disabled, standard POJOs can only be bound from JSON `null` or
      * JSON Object (standard meaning that no custom deserializers or
      * constructors are defined; both of which can add support for other

src/main/java/tools/jackson/databind/SerializationFeature.java

@@ -68,9 +68,9 @@ public enum SerializationFeature implements ConfigFeature
      * (like <code>@JsonSerialize</code>): ones that do have annotations
      * do not result in an exception being thrown.
      *<p>
-     * Feature is enabled by default.
+     * Feature is disabled by default as of Jackson 3.0 (in 2.x it was enabled).
      */
-    FAIL_ON_EMPTY_BEANS(true),
+    FAIL_ON_EMPTY_BEANS(false),
 
     /**
      * Feature that determines what happens when a direct self-reference

src/test/java/tools/jackson/databind/convert/BeanConversionsTest.java

@@ -11,7 +11,6 @@
 import tools.jackson.databind.*;
 import tools.jackson.databind.annotation.JsonDeserialize;
 import tools.jackson.databind.annotation.JsonSerialize;
-import tools.jackson.databind.exc.InvalidDefinitionException;
 import tools.jackson.databind.exc.InvalidFormatException;
 import tools.jackson.databind.exc.UnrecognizedPropertyException;
 import tools.jackson.databind.util.StdConverter;
@@ -248,25 +247,10 @@ public void testIssue11() throws Exception
 
         // And one more: this time with a minor twist
         final Object plaino = new Object();
-        // first, a failed attempt:
-        try {
-            m = MAPPER.convertValue(plaino, Map.class);
-            fail("Conversion should have failed");
-        } catch (InvalidDefinitionException e) {
-            verifyException(e, "no properties discovered");
-        }
-
-        ObjectMapper mapper = jsonMapperBuilder()
-                .disable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
-                .build();
-        try {
-            assertEquals("{}", mapper.writer()
-                    .writeValueAsString(plaino));
-        } catch (Exception e) {
-            throw (Exception) e.getCause();
-        }
+        assertEquals("{}", MAPPER.writer()
+                .writeValueAsString(plaino));
         // should now work, via serialization/deserialization:
-        m = mapper.convertValue(plaino, Map.class);
+        m = MAPPER.convertValue(plaino, Map.class);
         assertNotNull(m);
         assertEquals(0, m.size());
     }

src/test/java/tools/jackson/databind/deser/jdk/VoidProperties2675Test.java

@@ -28,12 +28,15 @@ static class VoidBean {
      */
 
     private final ObjectMapper VOID_MAPPER = jsonMapperBuilder()
+            .enable(MapperFeature.ALLOW_VOID_VALUED_PROPERTIES)
             .enable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
+            .enable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
             .build();
 
     private final ObjectMapper NO_VOID_MAPPER = jsonMapperBuilder()
             .disable(MapperFeature.ALLOW_VOID_VALUED_PROPERTIES)
             .enable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
+            .enable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
             .build();
 
     @Test
@@ -42,8 +45,8 @@ public void testVoidBeanSerialization() throws Exception
         // with 3.x enabled by default, but may disable
         assertEquals("{\"value\":null}", VOID_MAPPER.writeValueAsString(new VoidBean()));
         try {
-            NO_VOID_MAPPER.writeValueAsString(new VoidBean());
-            fail("Should not pass");
+            String json = NO_VOID_MAPPER.writeValueAsString(new VoidBean());
+            fail("Should not pass; got: "+json);
         } catch (InvalidDefinitionException e) {
             verifyException(e, "no properties discovered");
         }

src/test/java/tools/jackson/databind/module/SimpleModuleTest.java

@@ -210,7 +210,11 @@ public void serialize(Test3787Bean value, JsonGenerator gen, SerializationContex
     @Test
     public void testWithoutModule()
     {
-        ObjectMapper mapper = jsonMapperBuilder().enable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES).build();
+        ObjectMapper mapper = jsonMapperBuilder()
+                .enable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
+                // since 3.0 not enabled by default
+                .enable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
+                .build();
         // first: serialization failure:
         try {
             mapper.writeValueAsString(new CustomBean("foo", 3));

src/test/java/tools/jackson/databind/ser/TestEmptyClass.java

@@ -64,7 +64,9 @@ public void testEmptyWithAnnotations() throws Exception
     {
         // First: without annotations, should complain
         try {
-            MAPPER.writeValueAsString(new Empty());
+            MAPPER.writer()
+                .with(SerializationFeature.FAIL_ON_EMPTY_BEANS)
+                    .writeValueAsString(new Empty());
             fail("Should fail");
         } catch (InvalidDefinitionException e) {
             verifyException(e, "No serializer found for class");
@@ -87,11 +89,10 @@ public void testEmptyWithAnnotations() throws Exception
     @Test
     public void testEmptyWithFeature() throws Exception
     {
-        // should be enabled by default
-        assertTrue(MAPPER.isEnabled(SerializationFeature.FAIL_ON_EMPTY_BEANS));
+        // should be disabled by default as of 3.x
+        assertFalse(MAPPER.isEnabled(SerializationFeature.FAIL_ON_EMPTY_BEANS));
         assertEquals("{}",
                 MAPPER.writer()
-                    .without(SerializationFeature.FAIL_ON_EMPTY_BEANS)
                     .writeValueAsString(new Empty()));
     }
 

src/test/java/tools/jackson/databind/ser/TestSerConfig.java

@@ -77,16 +77,17 @@ public void testDefaults()
     {
         SerializationConfig cfg = MAPPER.serializationConfig();
 
-        // First, defaults:
         assertTrue(cfg.isEnabled(MapperFeature.USE_ANNOTATIONS));
         assertTrue(cfg.isEnabled(MapperFeature.CAN_OVERRIDE_ACCESS_MODIFIERS));
 
         assertTrue(cfg.isEnabled(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS));
 
-        assertFalse(cfg.isEnabled(SerializationFeature.INDENT_OUTPUT));
+        assertEquals(MapperFeature.DEFAULT_VIEW_INCLUSION.enabledByDefault(),
+                cfg.isEnabled(MapperFeature.DEFAULT_VIEW_INCLUSION));
         assertFalse(cfg.isEnabled(MapperFeature.USE_STATIC_TYPING));
-        assertTrue(cfg.isEnabled(SerializationFeature.FAIL_ON_EMPTY_BEANS));
-        assertTrue(cfg.isEnabled(MapperFeature.DEFAULT_VIEW_INCLUSION));
+        assertEquals(SerializationFeature.FAIL_ON_EMPTY_BEANS.enabledByDefault(),
+                cfg.isEnabled(SerializationFeature.FAIL_ON_EMPTY_BEANS));
+        assertFalse(cfg.isEnabled(SerializationFeature.INDENT_OUTPUT));
     }
 
     @Test