[Spring] Format datetime in rfc3339 (#3777)

* [spring-boot] format datetime in rfc3339

See #3727

* [spring-mvc] format datetime in rfc3339

samples/server/petstore/spring-mvc-j8-async/src/main/java/io/swagger/api/FakeApi.java

@@ -1,8 +1,8 @@
 package io.swagger.api;
 
 import io.swagger.model.Client;
-import java.time.LocalDate;
 import java.time.OffsetDateTime;
+import java.time.LocalDate;
 import java.math.BigDecimal;
 
 import io.swagger.annotations.*;

samples/server/petstore/spring-mvc-j8-async/src/main/java/io/swagger/api/PetApi.java

@@ -1,8 +1,8 @@
 package io.swagger.api;
 
 import io.swagger.model.Pet;
-import java.io.File;
 import io.swagger.model.ModelApiResponse;
+import java.io.File;
 
 import io.swagger.annotations.*;
 import org.springframework.http.HttpStatus;

samples/server/petstore/spring-mvc-j8-async/src/main/java/io/swagger/configuration/RFC3339DateFormat.java

@@ -0,0 +1,20 @@
+package io.swagger.configuration;
+
+import com.fasterxml.jackson.databind.util.ISO8601DateFormat;
+import com.fasterxml.jackson.databind.util.ISO8601Utils;
+
+import java.text.FieldPosition;
+import java.util.Date;
+
+
+public class RFC3339DateFormat extends ISO8601DateFormat {
+
+  // Same as ISO8601DateFormat but serializing milliseconds.
+  @Override
+  public StringBuffer format(Date date, StringBuffer toAppendTo, FieldPosition fieldPosition) {
+    String value = ISO8601Utils.format(date, true);
+    toAppendTo.append(value);
+    return toAppendTo;
+  }
+
+}

samples/server/petstore/spring-mvc-j8-async/src/main/java/io/swagger/configuration/SwaggerUiConfiguration.java

@@ -1,14 +1,21 @@
 package io.swagger.configuration;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.PropertySource;
 import org.springframework.context.annotation.Import;
+import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
+import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
 import org.springframework.web.servlet.config.annotation.EnableWebMvc;
 import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
 import springfox.documentation.swagger2.annotations.EnableSwagger2;
 
+import java.util.List;
+
 
 @Configuration
 @ComponentScan(basePackages = "io.swagger.api")
@@ -51,4 +58,14 @@ public class SwaggerUiConfiguration extends WebMvcConfigurerAdapter {
     }
   }
 
+  @Override
+  public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
+    ObjectMapper objectMapper = Jackson2ObjectMapperBuilder.json()
+        .featuresToDisable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+        .dateFormat( new RFC3339DateFormat())
+        .build();
+    converters.add(new MappingJackson2HttpMessageConverter(objectMapper));
+    super.configureMessageConverters(converters);
+  }
+
 }