Fix Writer lifecycle for writeInternal(Object, Type, Writer)

Closes gh-36565

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

@@ -127,6 +127,7 @@ public abstract class AbstractJsonHttpMessageConverter extends AbstractGenericHt
 		catch (Exception ex) {
 			throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
 		}
+		writer.close();
 	}
 
 

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

@@ -105,7 +105,6 @@ public class GsonHttpMessageConverter extends AbstractJsonHttpMessageConverter {
 		else {
 			getGson().toJson(object, writer);
 		}
-		writer.flush();
 	}
 
 	@Override