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POSpring Ajax - @ResponseBody - Returning null response
 

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  1. POSpring Ajax - @ResponseBody - Returning null response
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    <p>In my spring webapp, I have an ajax servlet that answer json (using jackson):</p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:util="http://www.springframework.org/schema/util" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.2.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.2.xsd"&gt; &lt;context:component-scan base-package="com.myapp.ajax" /&gt; &lt;util:list id="messageConvertersList"&gt; &lt;bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"&gt; &lt;property name="supportedMediaTypes"&gt; &lt;list&gt; &lt;value&gt;application/json;charset=UTF-8&lt;/value&gt; &lt;/list&gt; &lt;/property&gt; &lt;/bean&gt; &lt;/util:list&gt; &lt;bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"&gt; &lt;property name="messageConverters" ref="messageConvertersList" /&gt; &lt;/bean&gt; &lt;bean id="handlerMapping" class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping" /&gt; &lt;mvc:interceptors&gt; &lt;mvc:interceptor&gt; &lt;mvc:mapping path="/**" /&gt; &lt;bean id="localeChangeInterceptor" class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor"&gt; &lt;property name="paramName" value="lang" /&gt; &lt;/bean&gt; &lt;/mvc:interceptor&gt; &lt;/mvc:interceptors&gt; &lt;bean id="localeResolver" class="org.springframework.web.servlet.i18n.SessionLocaleResolver" /&gt; &lt;bean id="handlerExceptionResolver" class="com.myapp.ajax.AjaxExceptionHandlerResolver"&gt; &lt;property name="exceptionHandler"&gt; &lt;bean class="com.myapp.ajax.AjaxExceptionHandler" /&gt; &lt;/property&gt; &lt;property name="messageConverters" ref="messageConvertersList" /&gt; &lt;/bean&gt; </code></pre> <p></p> <p>I have the following ajax service:</p> <pre><code>@RequestMapping(value = "getLoggedUser") @ResponseBody public DtoUser getLoggedUser() { return authenticationService.getLoggedUser(); } </code></pre> <p>When the user is logged in it returns something like:</p> <pre><code>{ userName : "jojo", email : "john.doe@email.com", firstName : "John", lastName : "Doe" } </code></pre> <p>When the user is not logged in, the expected behavior is to return</p> <pre><code>null </code></pre> <p>But it returns an empty response which is not a valid JSON response (and additionally with a bad Content-type header)</p> <p>Why is this happening ?<br> Do I have solutions to obtain the expected behaviour ?</p>
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    1. COI would think the empty json would be the proper behavior if you are returning a null object, not returning the string "null". What is being returned as the content type? If you are trying to follow a more RESTful pattern, the best solution would be to return an appropriate HTTP status code, like a 404 (not found) or a 401 (not authorized). Or, better yet, redirect/forward them to the login page.
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    2. COAn empty json would mean that I have to test a property (ex: response.email) to know if the user is null or not. It why I think returning null is more proper and coherent
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