Optimize InstantDeserializer replaceZeroOffsetAsZIfNecessary (#266)

Author: schlosna

datetime/src/main/java/com/fasterxml/jackson/datatype/jsr310/deser/InstantDeserializer.java

@@ -54,13 +54,6 @@ public class InstantDeserializer<T extends Temporal>
 {
     private static final long serialVersionUID = 1L;
 
-    /**
-     * Constants used to check if the time offset is zero. See [jackson-modules-java8#18]
-     *
-     * @since 2.9.0
-     */
-    private static final Pattern ISO8601_UTC_ZERO_OFFSET_SUFFIX_REGEX = Pattern.compile("\\+00:?(00)?$");
-
     /**
      * Constants used to check if ISO 8601 time string is colonless. See [jackson-modules-java8#131]
      *
@@ -226,7 +219,7 @@ public T deserialize(JsonParser parser, DeserializationContext context) throws I
                 return (T) parser.getEmbeddedObject();
 
             case JsonTokenId.ID_START_ARRAY:
-            	return _deserializeFromArray(parser, context);
+                return _deserializeFromArray(parser, context);
         }
         return _handleUnexpectedToken(context, parser, JsonToken.VALUE_STRING,
                 JsonToken.VALUE_NUMBER_INT, JsonToken.VALUE_NUMBER_FLOAT);
@@ -337,12 +330,37 @@ private ZoneId getZone(DeserializationContext context)
     private String replaceZeroOffsetAsZIfNecessary(String text)
     {
         if (replaceZeroOffsetAsZ) {
-            return ISO8601_UTC_ZERO_OFFSET_SUFFIX_REGEX.matcher(text).replaceFirst("Z");
+            return replaceZeroOffsetAsZ(text);
         }
 
         return text;
     }
 
+    private static String replaceZeroOffsetAsZ(String text)
+    {
+        int plusIndex = text.lastIndexOf('+');
+        if (plusIndex < 0) {
+            return text;
+        }
+        int maybeOffsetIndex = plusIndex + 1;
+        int remaining = text.length() - maybeOffsetIndex;
+        switch (remaining) {
+            case 2:
+                return text.regionMatches(maybeOffsetIndex, "00", 0, remaining)
+                        ? text.substring(0, plusIndex) + 'Z'
+                        : text;
+            case 4:
+                return text.regionMatches(maybeOffsetIndex, "0000", 0, remaining)
+                        ? text.substring(0, plusIndex) + 'Z'
+                        : text;
+            case 5:
+                return text.regionMatches(maybeOffsetIndex, "00:00", 0, remaining)
+                        ? text.substring(0, plusIndex) + 'Z'
+                        : text;
+        }
+        return text;
+    }
+
     // @since 2.13
     private String addInColonToOffsetIfMissing(String text)
     {

datetime/src/test/java/com/fasterxml/jackson/datatype/jsr310/deser/InstantDeserTest.java

@@ -23,6 +23,7 @@
 import static com.fasterxml.jackson.datatype.jsr310.deser.InstantDeserializer.ISO8601_COLONLESS_OFFSET_REGEX;
 import static org.junit.Assert.*;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assume.assumeTrue;
 
 public class InstantDeserTest extends ModuleTestBase
 {
@@ -434,10 +435,43 @@ public void testDeserializationFromStringWithZeroZoneOffset03() throws Exception
         assertEquals("The value is not correct.", date, result);
     }
 
+    @Test
+    public void testDeserializationFromStringWithZeroZoneOffset04() throws Exception {
+        assumeInstantCanParseOffsets();
+        Instant date = Instant.now();
+        String json = formatWithZeroZoneOffset(date, "+00:30");
+        Instant result = READER.readValue(json);
+        assertNotEquals("The value is not correct.", date, result);
+    }
+
+    @Test
+    public void testDeserializationFromStringWithZeroZoneOffset05() throws Exception {
+        assumeInstantCanParseOffsets();
+        Instant date = Instant.now();
+        String json = formatWithZeroZoneOffset(date, "+01:30");
+        Instant result = READER.readValue(json);
+        assertNotEquals("The value is not correct.", date, result);
+    }
+
+    @Test
+    public void testDeserializationFromStringWithZeroZoneOffset06() throws Exception {
+        assumeInstantCanParseOffsets();
+        Instant date = Instant.now();
+        String json = formatWithZeroZoneOffset(date, "-00:00");
+        Instant result = READER.readValue(json);
+        assertEquals("The value is not correct.", date, result);
+    }
+
     private String formatWithZeroZoneOffset(Instant date, String offset){
         return '"' + FORMATTER.format(date).replaceFirst("Z$", offset) + '"';
     }
 
+    private static void assumeInstantCanParseOffsets() {
+        // DateTimeFormatter.ISO_INSTANT didn't handle offsets until JDK 12+.
+        // This was added by https://bugs.openjdk.org/browse/JDK-8166138
+        assumeTrue(System.getProperty("java.specification.version").compareTo("12") > 0);
+    }
+
     /*
     /**********************************************************************
     /* Deserialization, misc other