Jackson2JsonTokenizer unwraps top level array only

When the input stream is a JSON array the tokenizer skips over the
start and end array tokens in order to decode into an array of
top-level objects. However in this mode it also skips over nested
start and end array tokens which prevents proper parsing of JSR-310
dates (represented with an array syntax) as well as any fields that
are collections.

Issue: SPR-15803

spring-web/src/main/java/org/springframework/http/codec/json/Jackson2Tokenizer.java

@@ -140,7 +140,7 @@ class Jackson2Tokenizer implements Function<DataBuffer, Flux<TokenBuffer>> {
 	}
 
 	private void processTokenArray(JsonToken token, List<TokenBuffer> result) throws IOException {
-		if (token != JsonToken.START_ARRAY && token != JsonToken.END_ARRAY) {
+		if (!isTopLevelArrayToken(token)) {
 			this.tokenBuffer.copyCurrentEvent(this.parser);
 		}
 
@@ -151,6 +151,11 @@ class Jackson2Tokenizer implements Function<DataBuffer, Flux<TokenBuffer>> {
 		}
 	}
 
+	private boolean isTopLevelArrayToken(JsonToken token) {
+		return (token == JsonToken.START_ARRAY && this.arrayDepth == 1) ||
+				(token == JsonToken.END_ARRAY && this.arrayDepth == 0);
+	}
+
 	public void endOfInput() {
 		this.inputFeeder.endOfInput();
 	}

spring-web/src/test/java/org/springframework/http/codec/json/Jackson2TokenizerTests.java

@@ -116,6 +116,19 @@ public class Jackson2TokenizerTests extends AbstractDataBufferAllocatingTestCase
 				asList("{\"foo\": \"bar\"}",
 						"{\"foo\": \"baz\"}"));
 
+		// SPR-15803
+		testTokenize(
+				singletonList("[" +
+						"{\"id\":\"0\",\"start\":[-999999999,1,1],\"end\":[999999999,12,31]}," +
+						"{\"id\":\"1\",\"start\":[-999999999,1,1],\"end\":[999999999,12,31]}," +
+						"{\"id\":\"2\",\"start\":[-999999999,1,1],\"end\":[999999999,12,31]}" +
+						"]"),
+				asList(
+						"{\"id\":\"0\",\"start\":[-999999999,1,1],\"end\":[999999999,12,31]}",
+						"{\"id\":\"1\",\"start\":[-999999999,1,1],\"end\":[999999999,12,31]}",
+						"{\"id\":\"2\",\"start\":[-999999999,1,1],\"end\":[999999999,12,31]}")
+		);
+
 		testTokenize(
 				asList("[{\"foo\": \"foofoo\", \"bar\"",
 						": \"barbar\"},{\"foo\": \"foofoofoo\", \"bar\": \"barbarbar\"}]"),