title: Jackson fails to serialize a null Double
body: <p>I am trying to serialize an object into an array and Jackson fails to do so with NPE.</p>
  
  <p>I am expecting something like [1, null, 10] in the response, but do not understand why Jackson throws NPE instead of serializing a null value.</p>
  
  <pre><code>@JsonFormat(shape = JsonFormat.Shape.ARRAY)
  public static class PointTO {
      private long x;
      private Double y;
      private int volume;
  
      public PointTO(long x, Double y, int volume) {
          this.x = x;
          this.y = y;
          this.volume = volume;
      }
  
      public long getX() {
          return x;
      }
  
      public Double getY() {
          return y;
      }
  
      public int getVolume() {
          return volume;
      }
  }
  </code></pre>
  
  <p>Here is the stack trace:</p>
  
  <pre><code>com.fasterxml.jackson.databind.JsonMappingException: (was java.lang.NullPointerException) (through reference chain: de.bnext.web.model.DisplayOrderBookResponseTO["curves"]-&amp;gt;java.util.ArrayList[0]-&amp;gt;de.bnext.web.model.CurveTO["points"]-&amp;gt;java.util.ArrayList[15]-&amp;gt;de.bnext.web.model.PointTO["y"])
      com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:232)
      com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:197)
      com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:183)
      com.fasterxml.jackson.databind.ser.impl.BeanAsArraySerializer.serializeAsArray(BeanAsArraySerializer.java:192)
      com.fasterxml.jackson.databind.ser.impl.BeanAsArraySerializer.serialize(BeanAsArraySerializer.java:147)
      com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContents(IndexedListSerializer.java:94)
      com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContents(IndexedListSerializer.java:21)
      com.fasterxml.jackson.databind.ser.std.AsArraySerializerBase.serialize(AsArraySerializerBase.java:180)
      com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:544)
      com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:551)
      com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:143)
      com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContents(IndexedListSerializer.java:94)
      com.fasterxml.jackson.databind.ser.impl.IndexedListSerializer.serializeContents(IndexedListSerializer.java:21)
      com.fasterxml.jackson.databind.ser.std.AsArraySerializerBase.serialize(AsArraySerializerBase.java:180)
      com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:544)
      com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:551)
      com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:143)
      com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:120)
      com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:1728)
      org.springframework.http.converter.json.MappingJackson2HttpMessageConverter.writeInternal(MappingJackson2HttpMessageConverter.java:194)
      org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:179)
      org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:148)
      org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:90)
      org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:189)
      org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:69)
      org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:122)
      org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
      org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
      org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
      org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
      org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
      org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:920)
      org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:827)
      javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
      org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:801)
      javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
      org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:368)
      org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:109)
      org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)
      org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)
      org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:97)
      org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)
      org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:100)
      org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)
      org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)
      org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)
      org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:35)
      org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)
      org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:105)
      org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)
      org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:79)
      org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:380)
      org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:169)
      org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
      org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)
  </code></pre>