Optimize Jackson resource management in codecs

Prior to this commit, references to `JsonGenerator` and
`ByteArrayBuilder` were not closed/released within codecs calls.
This prevents Jackson from reusing more efficiently shared memory
resources.

This commit properly closes/releases Jackson resources in Spring MVC,
Spring WebFlux and Spring Messaging codecs.
A benchmark on WebFlux codecs (in both single value/streaming mode)
shows significant throughput and allocation improvements for small
payloads.

Closes gh-25910

spring-messaging/src/main/java/org/springframework/messaging/converter/MappingJackson2MessageConverter.java

@@ -263,14 +263,15 @@ public class MappingJackson2MessageConverter extends AbstractMessageConverter {
 			if (byte[].class == getSerializedPayloadClass()) {
 				ByteArrayOutputStream out = new ByteArrayOutputStream(1024);
 				JsonEncoding encoding = getJsonEncoding(getMimeType(headers));
-				JsonGenerator generator = this.objectMapper.getFactory().createGenerator(out, encoding);
-				if (view != null) {
-					this.objectMapper.writerWithView(view).writeValue(generator, payload);
-				}
-				else {
-					this.objectMapper.writeValue(generator, payload);
+				try (JsonGenerator generator = this.objectMapper.getFactory().createGenerator(out, encoding)) {
+					if (view != null) {
+						this.objectMapper.writerWithView(view).writeValue(generator, payload);
+					}
+					else {
+						this.objectMapper.writeValue(generator, payload);
+					}
+					payload = out.toByteArray();
 				}
-				payload = out.toByteArray();
 			}
 			else {
 				// Assuming a text-based target payload

spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Encoder.java

@@ -149,7 +149,16 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 
 					return Flux.from(inputStream)
 							.map(value -> encodeStreamingValue(value, bufferFactory, hints, sequenceWriter, byteBuilder,
-									separator));
+									separator))
+							.doAfterTerminate(() -> {
+								try {
+									byteBuilder.release();
+									generator.close();
+								}
+								catch (IOException ex) {
+									logger.error("Could not close Encoder resources", ex);
+								}
+							});
 				}
 				catch (IOException ex) {
 					return Flux.error(ex);
@@ -172,30 +181,34 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 
 		ObjectWriter writer = createObjectWriter(valueType, mimeType, hints);
 		ByteArrayBuilder byteBuilder = new ByteArrayBuilder(writer.getFactory()._getBufferRecycler());
-		JsonEncoding encoding = getJsonEncoding(mimeType);
+		try {
+			JsonEncoding encoding = getJsonEncoding(mimeType);
 
-		logValue(hints, value);
+			logValue(hints, value);
 
-		try {
-			JsonGenerator generator = getObjectMapper().getFactory().createGenerator(byteBuilder, encoding);
-			writer.writeValue(generator, value);
-			generator.flush();
-		}
-		catch (InvalidDefinitionException ex) {
-			throw new CodecException("Type definition error: " + ex.getType(), ex);
-		}
-		catch (JsonProcessingException ex) {
-			throw new EncodingException("JSON encoding error: " + ex.getOriginalMessage(), ex);
-		}
-		catch (IOException ex) {
-			throw new IllegalStateException("Unexpected I/O error while writing to byte array builder", ex);
-		}
+			try (JsonGenerator generator = getObjectMapper().getFactory().createGenerator(byteBuilder, encoding)) {
+				writer.writeValue(generator, value);
+				generator.flush();
+			}
+			catch (InvalidDefinitionException ex) {
+				throw new CodecException("Type definition error: " + ex.getType(), ex);
+			}
+			catch (JsonProcessingException ex) {
+				throw new EncodingException("JSON encoding error: " + ex.getOriginalMessage(), ex);
+			}
+			catch (IOException ex) {
+				throw new IllegalStateException("Unexpected I/O error while writing to byte array builder", ex);
+			}
 
-		byte[] bytes = byteBuilder.toByteArray();
-		DataBuffer buffer = bufferFactory.allocateBuffer(bytes.length);
-		buffer.write(bytes);
+			byte[] bytes = byteBuilder.toByteArray();
+			DataBuffer buffer = bufferFactory.allocateBuffer(bytes.length);
+			buffer.write(bytes);
 
-		return buffer;
+			return buffer;
+		}
+		finally {
+			byteBuilder.release();
+		}
 	}
 
 	private DataBuffer encodeStreamingValue(Object value, DataBufferFactory bufferFactory, @Nullable Map<String, Object> hints,

spring-web/src/main/java/org/springframework/http/converter/json/AbstractJackson2HttpMessageConverter.java

@@ -307,8 +307,8 @@ public abstract class AbstractJackson2HttpMessageConverter extends AbstractGener
 
 		MediaType contentType = outputMessage.getHeaders().getContentType();
 		JsonEncoding encoding = getJsonEncoding(contentType);
-		JsonGenerator generator = this.objectMapper.getFactory().createGenerator(outputMessage.getBody(), encoding);
-		try {
+
+		try (JsonGenerator generator = this.objectMapper.getFactory().createGenerator(outputMessage.getBody(), encoding)) {
 			writePrefix(generator, object);
 
 			Object value = object;

spring-web/src/test/resources/log4j2-test.xml

@@ -6,7 +6,7 @@
 		</Console>
 	</Appenders>
 	<Loggers>
-		<Logger name="org.springframework.web" level="debug" />
+		<Logger name="org.springframework.web" level="warn" />
 		<Logger name="org.springframework.beans" level="warn" />
 		<Logger name="org.springframework.binding" level="warn" />
 		<Logger name="org.springframework.http" level="warn" />

spring-webmvc/src/main/java/org/springframework/web/servlet/view/json/AbstractJackson2View.java

@@ -206,29 +206,30 @@ public abstract class AbstractJackson2View extends AbstractView {
 	 * @throws IOException if writing failed
 	 */
 	protected void writeContent(OutputStream stream, Object object) throws IOException {
-		JsonGenerator generator = this.objectMapper.getFactory().createGenerator(stream, this.encoding);
-		writePrefix(generator, object);
-
-		Object value = object;
-		Class<?> serializationView = null;
-		FilterProvider filters = null;
-
-		if (value instanceof MappingJacksonValue) {
-			MappingJacksonValue container = (MappingJacksonValue) value;
-			value = container.getValue();
-			serializationView = container.getSerializationView();
-			filters = container.getFilters();
-		}
+		try (JsonGenerator generator = this.objectMapper.getFactory().createGenerator(stream, this.encoding)) {
+			writePrefix(generator, object);
+
+			Object value = object;
+			Class<?> serializationView = null;
+			FilterProvider filters = null;
+
+			if (value instanceof MappingJacksonValue) {
+				MappingJacksonValue container = (MappingJacksonValue) value;
+				value = container.getValue();
+				serializationView = container.getSerializationView();
+				filters = container.getFilters();
+			}
 
-		ObjectWriter objectWriter = (serializationView != null ?
-				this.objectMapper.writerWithView(serializationView) : this.objectMapper.writer());
-		if (filters != null) {
-			objectWriter = objectWriter.with(filters);
-		}
-		objectWriter.writeValue(generator, value);
+			ObjectWriter objectWriter = (serializationView != null ?
+					this.objectMapper.writerWithView(serializationView) : this.objectMapper.writer());
+			if (filters != null) {
+				objectWriter = objectWriter.with(filters);
+			}
+			objectWriter.writeValue(generator, value);
 
-		writeSuffix(generator, object);
-		generator.flush();
+			writeSuffix(generator, object);
+			generator.flush();
+		}
 	}