Stream custom types in Jackson2JsonEncoder

Issue: SPR-15727

spring-web/src/main/java/org/springframework/http/codec/json/Jackson2JsonEncoder.java

@@ -124,7 +124,7 @@ public class Jackson2JsonEncoder extends Jackson2CodecSupport implements HttpMes
 			return Flux.from(inputStream).map(value ->
 					encodeValue(value, mimeType, bufferFactory, elementType, hints));
 		}
-		else if (MediaType.APPLICATION_STREAM_JSON.isCompatibleWith(mimeType)) {
+		else if (this.streamingMediaTypes.stream().anyMatch(streamingMediaType -> streamingMediaType.isCompatibleWith(mimeType))) {
 			return Flux.from(inputStream).map(value -> {
 				DataBuffer buffer = encodeValue(value, mimeType, bufferFactory, elementType, hints);
 				buffer.write(new byte[]{'\n'});

spring-web/src/test/java/org/springframework/http/codec/json/Jackson2JsonEncoderTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.http.codec.json;
 
+import java.util.Arrays;
 import java.util.Map;
 
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
@@ -32,6 +33,7 @@ import reactor.test.StepVerifier;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.io.buffer.AbstractDataBufferAllocatingTestCase;
 import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.http.MediaType;
 import org.springframework.http.codec.Pojo;
 import org.springframework.http.codec.ServerSentEvent;
 
@@ -108,6 +110,26 @@ public class Jackson2JsonEncoderTests extends AbstractDataBufferAllocatingTestCa
 				.verifyComplete();
 	}
 
+	@Test  // SPR-15727
+	public void encodeAsStreamWithCustomStreamingType() throws Exception {
+		MediaType fooMediaType = new MediaType("application", "foo");
+		MediaType barMediaType = new MediaType("application", "bar");
+		this.encoder.setStreamingMediaTypes(Arrays.asList(fooMediaType, barMediaType));
+		Flux<Pojo> source = Flux.just(
+				new Pojo("foo", "bar"),
+				new Pojo("foofoo", "barbar"),
+				new Pojo("foofoofoo", "barbarbar")
+		);
+		ResolvableType type = ResolvableType.forClass(Pojo.class);
+		Flux<DataBuffer> output = this.encoder.encode(source, this.bufferFactory, type, barMediaType, emptyMap());
+
+		StepVerifier.create(output)
+				.consumeNextWith(stringConsumer("{\"foo\":\"foo\",\"bar\":\"bar\"}\n"))
+				.consumeNextWith(stringConsumer("{\"foo\":\"foofoo\",\"bar\":\"barbar\"}\n"))
+				.consumeNextWith(stringConsumer("{\"foo\":\"foofoofoo\",\"bar\":\"barbarbar\"}\n"))
+				.verifyComplete();
+	}
+
 	@Test
 	public void fieldLevelJsonView() throws Exception {
 		JacksonViewBean bean = new JacksonViewBean();