springboot 接口返回数据时 net.sf.json.JSONNull["empty"]) 异常

@ResetController返回数据时出现异常

Could not write JSON: Object is null; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Object is null (through reference chain: com.banxue.common.entity.ReturnEntity["data"]->net.sf.json.JSONObject["inviteRecord"]->net.sf.json.JSONArray[0]->net.sf.json.JSONObject["exchange_id"]->net.sf.json.JSONNull["empty"])
org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: Object is null; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Object is null (through reference chain: com.banxue.common.entity.ReturnEntity["data"]->net.sf.json.JSONObject["inviteRecord"]->net.sf.json.JSONArray[0]->net.sf.json.JSONObject["exchange_id"]->net.sf.json.JSONNull["empty"])
    at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:293)
    at org.springframework.http.converter.AbstractGenericHttpMessageConverter.write(AbstractGenericHttpMessageConverter.java:106)
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:231)
    at org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:203)
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:81)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:113)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
    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:635)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

解决方法1：

@Bean
public ObjectMapper objectMapper(){
    return new ObjectMapper().setSerializationInclusion(JsonInclude.Include.NON_NULL);
}

　　

解决方法2：

使用fastjson 先转换成字符串