[Spring] Could not write JSON: Object is null

HTTP Status 500 - Could not write JSON: Object is null (through reference chain: net.sf.json.JSONObject["rows"]->net.sf.json.JSONArray[0]->net.sf.json.JSONObject["uploadfile"]->net.sf.json.JSONNull["empty"]); nested exception is org.codehaus.jackson.map.JsonMappingException: Object is null (through reference chain: net.sf.json.JSONObject["rows"]->net.sf.json.JSONArray[0]->net.sf.json.JSONObject["uploadfile"]->net.sf.json.JSONNull["empty"])

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type Exception report

message Could not write JSON: Object is null (through reference chain: net.sf.json.JSONObject["rows"]->net.sf.json.JSONArray[0]->net.sf.json.JSONObject["uploadfile"]->net.sf.json.JSONNull["empty"]); nested exception is org.codehaus.jackson.map.JsonMappingException: Object is null (through reference chain: net.sf.json.JSONObject["rows"]->net.sf.json.JSONArray[0]->net.sf.json.JSONObject["uploadfile"]->net.sf.json.JSONNull["empty"])

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Object is null (through reference chain: net.sf.json.JSONObject["rows"]->net.sf.json.JSONArray[0]->net.sf.json.JSONObject["uploadfile"]->net.sf.json.JSONNull["empty"]); nested exception is org.codehaus.jackson.map.JsonMappingException: Object is null (through reference chain: net.sf.json.JSONObject["rows"]->net.sf.json.JSONArray[0]->net.sf.json.JSONObject["uploadfile"]->net.sf.json.JSONNull["empty"])
	org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.writeInternal(MappingJacksonHttpMessageConverter.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:936)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

root cause

org.codehaus.jackson.map.JsonMappingException: Object is null (through reference chain: net.sf.json.JSONObject["rows"]->net.sf.json.JSONArray[0]->net.sf.json.JSONObject["uploadfile"]->net.sf.json.JSONNull["empty"])
	org.codehaus.jackson.map.JsonMappingException.wrapWithPath(JsonMappingException.java:218)
	org.codehaus.jackson.map.JsonMappingException.wrapWithPath(JsonMappingException.java:183)
	org.codehaus.jackson.map.ser.std.SerializerBase.wrapAndThrow(SerializerBase.java:140)
	org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:158)
	org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
	org.codehaus.jackson.map.ser.std.MapSerializer.serializeFields(MapSerializer.java:262)
	org.codehaus.jackson.map.ser.std.MapSerializer.serialize(MapSerializer.java:186)
	org.codehaus.jackson.map.ser.std.MapSerializer.serialize(MapSerializer.java:23)
	org.codehaus.jackson.map.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:72)
	org.codehaus.jackson.map.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:23)
	org.codehaus.jackson.map.ser.std.AsArraySerializerBase.serialize(AsArraySerializerBase.java:86)
	org.codehaus.jackson.map.ser.std.MapSerializer.serializeFields(MapSerializer.java:262)
	org.codehaus.jackson.map.ser.std.MapSerializer.serialize(MapSerializer.java:186)
	org.codehaus.jackson.map.ser.std.MapSerializer.serialize(MapSerializer.java:23)
	org.codehaus.jackson.map.ser.StdSerializerProvider._serializeValue(StdSerializerProvider.java:610)
	org.codehaus.jackson.map.ser.StdSerializerProvider.serializeValue(StdSerializerProvider.java:256)
	org.codehaus.jackson.map.ObjectMapper.writeValue(ObjectMapper.java:1613)
	org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.writeInternal(MappingJacksonHttpMessageConverter.java:191)
	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:936)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

root cause

net.sf.json.JSONException: Object is null
	net.sf.json.JSONNull.isEmpty(JSONNull.java:69)
	sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	java.lang.reflect.Method.invoke(Unknown Source)
	org.codehaus.jackson.map.ser.BeanPropertyWriter.get(BeanPropertyWriter.java:483)
	org.codehaus.jackson.map.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:418)
	org.codehaus.jackson.map.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:150)
	org.codehaus.jackson.map.ser.BeanSerializer.serialize(BeanSerializer.java:112)
	org.codehaus.jackson.map.ser.std.MapSerializer.serializeFields(MapSerializer.java:262)
	org.codehaus.jackson.map.ser.std.MapSerializer.serialize(MapSerializer.java:186)
	org.codehaus.jackson.map.ser.std.MapSerializer.serialize(MapSerializer.java:23)
	org.codehaus.jackson.map.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:72)
	org.codehaus.jackson.map.ser.std.CollectionSerializer.serializeContents(CollectionSerializer.java:23)
	org.codehaus.jackson.map.ser.std.AsArraySerializerBase.serialize(AsArraySerializerBase.java:86)
	org.codehaus.jackson.map.ser.std.MapSerializer.serializeFields(MapSerializer.java:262)
	org.codehaus.jackson.map.ser.std.MapSerializer.serialize(MapSerializer.java:186)
	org.codehaus.jackson.map.ser.std.MapSerializer.serialize(MapSerializer.java:23)
	org.codehaus.jackson.map.ser.StdSerializerProvider._serializeValue(StdSerializerProvider.java:610)
	org.codehaus.jackson.map.ser.StdSerializerProvider.serializeValue(StdSerializerProvider.java:256)
	org.codehaus.jackson.map.ObjectMapper.writeValue(ObjectMapper.java:1613)
	org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.writeInternal(MappingJacksonHttpMessageConverter.java:191)
	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:936)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:620)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)

note The full stack trace of the root cause is available in the Apache Tomcat/7.0.57 logs.

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Apache Tomcat/7.0.57

사용하던 net.sf.json-lib JSON 라이브러리가 NULL인 변수를 JSON으로 변환하지 못해서 생기는 에러

org.json.simple의 라이브러리를 사용하니까 문제가 해결됨

참고 - http://blog.naver.com/limeof/220596002626