add JsonMapper builderWithJackson2Defaults() (#5004)

Author: pjfanning

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

@@ -318,7 +318,7 @@ public enum DeserializationFeature implements ConfigFeature
      * <p>
      * NOTE: only <b>single</b> wrapper Array is allowed: if multiple attempted, exception
      * will be thrown.
-     *
+     * <p>
      * Feature is disabled by default.
      */
     UNWRAP_SINGLE_VALUE_ARRAYS(false),
@@ -330,7 +330,7 @@ public enum DeserializationFeature implements ConfigFeature
      * a single property with expected root name. If not, a
      * {@link DatabindException} is thrown; otherwise value of the wrapped property
      * will be deserialized as if it was the root value.
-     *<p>
+     * <p>
      * Feature is disabled by default.
      */
     UNWRAP_ROOT_VALUE(false),

src/main/java/tools/jackson/databind/cfg/MapperBuilder.java

@@ -798,6 +798,25 @@ public B configure(DatatypeFeature feature, boolean state) {
         return _this();
     }
 
+    /**
+     * The builder returned uses default settings more closely
+     * matching the default configs used in Jackson 2.x versions.
+     * <p>
+     *     This method is still a work in progress and may not yet fully replicate the
+     *     default settings of Jackson 2.x.
+     * </p>
+     */
+    public B configureForJackson2() {
+        return enable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
+                .enable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+                .enable(SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS)
+                .disable(SerializationFeature.WRITE_ENUMS_USING_TO_STRING)
+                .enable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
+                .disable(DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES)
+                .disable(DeserializationFeature.FAIL_ON_TRAILING_TOKENS)
+                .disable(DeserializationFeature.READ_ENUMS_USING_TO_STRING);
+    }
+
     /*
     /**********************************************************************
     /* Changing features: parser, generator

src/main/java/tools/jackson/databind/json/JsonMapper.java

@@ -142,17 +142,31 @@ public JsonMapper(Builder b) {
     /**********************************************************************
      */
 
-    public static JsonMapper.Builder builder() {
+    public static Builder builder() {
         return new Builder(new JsonFactory());
     }
 
     public static Builder builder(JsonFactory streamFactory) {
         return new Builder(streamFactory);
     }
 
+    /**
+     * Modifies the settings of this builder to more closely match the default configs used
+     * in Jackson 2.x versions.
+     * <p>
+     *     This method is still a work in progress and may not yet fully replicate the
+     *     default settings of Jackson 2.x.
+     * </p>
+     */
+    public static Builder builderWithJackson2Defaults() {
+        return builder(JsonFactory.builderWithJackson2Defaults().build())
+                .configureForJackson2();
+    }
+
+
     @SuppressWarnings("unchecked")
     @Override
-    public JsonMapper.Builder rebuild() {
+    public Builder rebuild() {
         return new Builder((Builder.StateImpl)_savedBuilderState);
     }
 

src/test/java/tools/jackson/databind/json/JsonMapperBuilderTest.java

@@ -0,0 +1,37 @@
+package tools.jackson.databind.json;
+
+import org.junit.jupiter.api.Test;
+import tools.jackson.core.StreamReadFeature;
+import tools.jackson.core.json.JsonFactory;
+import tools.jackson.core.json.JsonWriteFeature;
+import tools.jackson.databind.DeserializationFeature;
+import tools.jackson.databind.ObjectMapper;
+import tools.jackson.databind.SerializationFeature;
+import tools.jackson.databind.testutil.DatabindTestUtil;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+// Test(s) to verify behaviors in JsonMapper.Builder
+public class JsonMapperBuilderTest extends DatabindTestUtil
+{
+
+    @Test
+    public void testBuilderWithJackson2Defaults()
+    {
+        ObjectMapper mapper = JsonMapper.builderWithJackson2Defaults().build();
+        JsonFactory jsonFactory = (JsonFactory) mapper.tokenStreamFactory();
+        assertFalse(mapper.isEnabled(StreamReadFeature.USE_FAST_DOUBLE_PARSER));
+        assertFalse(mapper.isEnabled(StreamReadFeature.USE_FAST_BIG_NUMBER_PARSER));
+        assertFalse(jsonFactory.isEnabled(JsonWriteFeature.ESCAPE_FORWARD_SLASHES));
+        assertFalse(jsonFactory.isEnabled(JsonWriteFeature.COMBINE_UNICODE_SURROGATES_IN_UTF8));
+        assertTrue(mapper.isEnabled(SerializationFeature.FAIL_ON_EMPTY_BEANS));
+        assertTrue(mapper.isEnabled(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS));
+        assertTrue(mapper.isEnabled(SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS));
+        assertFalse(mapper.isEnabled(SerializationFeature.WRITE_ENUMS_USING_TO_STRING));
+        assertTrue(mapper.isEnabled(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES));
+        assertFalse(mapper.isEnabled(DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES));
+        assertFalse(mapper.isEnabled(DeserializationFeature.FAIL_ON_TRAILING_TOKENS));
+        assertFalse(mapper.isEnabled(DeserializationFeature.READ_ENUMS_USING_TO_STRING));
+    }
+}