title: Custom serializer for Object array using jackson
body: <p>Similar to this <a href="https://stackoverflow.com/questions/35832846/jackson-custom-serializer-for-propeties-inside-object">link</a> , i want to write custom serializer for an object array, but i want to handle each element differently i.e. if my array is as follows:</p>
  
  <pre><code>Object[] array = new Object[3] {new Date(), 1, "load"};
  </code></pre>
  
  <p>I only want to serialize the <code>Date</code> instance, others i want to send as is. For <code>Date</code> , i am able to handle but others i am unable to serialize. My code is as follows:</p>
  
  <pre><code>@Override
  public void serialize(Object[] array,
                        JsonGenerator gen,
                        SerializerProvider provider)
          throws IOException, JsonProcessingException {
      for(Object tempObject : array) {
          if(tempObject instanceof Date || tempObject instanceof String) {
              gen.writeString(tempObject.toString());
          } else if(tempObject instanceof Number) {
              gen.writeNumber(Integer.valueOf(tempObject.toString()));
          }
      }
  }
  </code></pre>
  
  <p><strong>EDIT</strong></p>
  
  <p>I am getting the following exception:</p>
  
  <pre><code>    org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: Can not write a number, expecting field name (context: Object); nested exception is com.fasterxml.jackson.core.JsonGenerationException: Can not write a number, expecting field name (context: Object)
          at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:271)
          at org.springframework.http.converter.AbstractGenericHttpMessageConverter.writeInternal(AbstractGenericHttpMessageConverter.java:110)
          at org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:193)
          at org.springframework.web.client.RestTemplate$HttpEntityRequestCallback.doWithRequest(RestTemplate.java:796)
          at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:589)
          at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:552)
          at org.springframework.web.client.RestTemplate.postForEntity(RestTemplate.java:379)
          at com.sungard.energy.aligne.aligneweb.gasoperations.scheduling.GasSchedulingController.findLegalEntitiesByDate(GasSchedulingController.java:131)
          at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
          at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
          at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
          at java.lang.reflect.Method.invoke(Unknown Source)
          at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
          at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
          at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:111)
          at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:806)
          at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:729)
          at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
          at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
          at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
          at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
          at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
          at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
          at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
          at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
          at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:841)
          at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1650)
          at org.eclipse.jetty.websocket.server.WebSocketUpgradeFilter.doFilter(WebSocketUpgradeFilter.java:206)
          at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1637)
          at com.thetransactioncompany.cors.CORSFilter.doFilter(CORSFilter.java:205)
          at com.thetransactioncompany.cors.CORSFilter.doFilter(CORSFilter.java:266)
          at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1637)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:316)
          at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:126)
          at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:90)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
          at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:114)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
          at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:122)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
          at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
          at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:169)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
          at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:48)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
          at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:205)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
          at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:120)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
          at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:64)
          at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
          at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:53)
          at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
          at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:91)
          at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
          at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:213)
          at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:176)
          at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
          at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262)
          at com.sungard.energy.aligne.aligneweb.commonservices.core.authentication.AligneWebDelegatingFilterProxy.doFilter(AligneWebDelegatingFilterProxy.java:23)
          at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1637)
          at com.sungard.energy.aligne.aligneweb.commonservices.core.authentication.AligneWebSSOSessionFilter.doFilter(AligneWebSSOSessionFilter.java:89)
          at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1637)
          at com.sungard.energy.aligne.aligneweb.commonservices.core.authentication.AligneWebSSOFilter.doFilter(AligneWebSSOFilter.java:47)
          at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1629)
          at org.apache.logging.log4j.web.Log4jServletFilter.doFilter(Log4jServletFilter.java:71)
          at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1637)
          at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:533)
          at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
          at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548)
          at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
          at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:190)
          at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1595)
          at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:188)
          at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1253)
          at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:168)
          at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:473)
          at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1564)
          at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:166)
          at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1155)
          at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
          at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:219)
          at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:126)
          at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
          at org.eclipse.jetty.server.Server.handle(Server.java:564)
          at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:317)
          at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:251)
          at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:279)
          at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:110)
          at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:124)
          at org.eclipse.jetty.util.thread.Invocable.invokePreferred(Invocable.java:128)
          at org.eclipse.jetty.util.thread.Invocable$InvocableExecutor.invoke(Invocable.java:222)
          at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:294)
          at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:199)
          at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:673)
          at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:591)
          at java.lang.Thread.run(Unknown Source)
  Caused by: com.fasterxml.jackson.core.JsonGenerationException: Can not write a number, expecting field name (context: Object)
          at com.fasterxml.jackson.core.JsonGenerator._reportError(JsonGenerator.java:1961)
          at com.fasterxml.jackson.core.json.JsonGeneratorImpl._reportCantWriteValueExpectName(JsonGeneratorImpl.java:244)
          at com.fasterxml.jackson.core.json.UTF8JsonGenerator._verifyValueWrite(UTF8JsonGenerator.java:1079)
          at com.fasterxml.jackson.core.json.UTF8JsonGenerator.writeString(UTF8JsonGenerator.java:445)
          at com.sungard.energy.aligne.aligneweb.gasoperations.scheduling.ObjectArraySerializer.serialize(GasSchedulingController.java:820)
          at com.sungard.energy.aligne.aligneweb.gasoperations.scheduling.ObjectArraySerializer.serialize(GasSchedulingController.java:1)
          at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727)
          at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719)
          at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155)
          at com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:727)
          at com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:719)
          at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:155)
          at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:480)
          at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:319)
          at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1396)
          at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:913)
          at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:264)
          ... 99 more
  </code></pre>
  
  <p><strong>EDIT 2</strong></p>
  
  <p>This is how i am registering my custom object mapper:</p>
  
  <pre><code>    HttpEntity&lt;SimplePipeServiceRequest&gt; request = new HttpEntity&lt;&gt;(AbstractGasService.createSimpleServiceRequest(serviceRequestDTO), headers);
      ObjectMapper mapper = new ObjectMapper();
      SimpleModule module = new SimpleModule("GasOpsModule");
      module.addSerializer(Object[].class, new ObjectArraySerializer());
      mapper.registerModule(module);
  </code></pre>