Spring's @RequestBody providing empty string on POST

Question

I have an application with Spring 3.0.5.RELEASE trying to get the full content of a post using @RequestBody. The method is called, but the string passed is always empty. I have checked, by placing breakpoints, that the StringHttpMessageConverter is called, but the inner HttpInputMessage is empty.

I've seen this issue with both Jetty and Tomcat, so I'm discarding it's a problem with the container.

Here is my sample controller:

@Controller
@RequestMapping("/")
public class SubscriptionController {
    @RequestMapping(value = "/requestbody", method = RequestMethod.POST)
    public ModelAndView mycustomAction(@RequestBody String body) {

        // body is always empty
        Logger.getLogger(this.getClass()).debug("REQUEST BODY '" + body + "'");
        return new ModelAndView("empty");
    }
}

My application context is defined as follows:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans 
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context 
        http://www.springframework.org/schema/context/spring-context-3.0.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

    <!-- Enable auto detection of controllers -->
    <context:component-scan base-package="com.big.viajerotelcel.controller" />

    <!--
        use annotation driven mvc and one single validator with JSR-303
        standard
    -->
    <mvc:annotation-driven />

    <!--
        Message source for this context, loaded from localized "messages_xx"
        files
    -->

    <bean id="messageSource"
        class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
        <property name="basenames" value="classpath:i18n/messages" />
        <property name="defaultEncoding" value="UTF-8" />
    </bean>

    <!-- Declare the Interceptor -->
    <mvc:interceptors>
        <bean class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor"
            p:paramName="locale" />
    </mvc:interceptors>

    <!-- Declare the Resolver -->
    <bean id="localeResolver"
        class="org.springframework.web.servlet.i18n.SessionLocaleResolver" />

    <!-- will load Tiles definitions! -->
    <bean id="tilesConfigurer"
        class="org.springframework.web.servlet.view.tiles2.TilesConfigurer">
        <property name="definitions">
            <list>
                <value>/WEB-INF/general.xml</value>
            </list>
        </property>
    </bean>

    <!-- Tiles view resolver -->
    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.UrlBasedViewResolver">
        <property name="viewClass"
            value="org.springframework.web.servlet.view.tiles2.TilesView" />
    </bean>

    <!-- Configure the multipart resolver -->
    <bean id="multipartResolver"
        class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!--
            one of the properties available; the maximum file size in bytes (5MB)
        -->
        <property name="maxUploadSize" value="5120000" />
    </bean>

    <!-- Adding these lines has no effect, the StringHttpMessageConverter is called either way -->
<!--    <bean id="stringHttpMessageConverter" class="org.springframework.http.converter.StringHttpMessageConverter"/>-->
<!--           -->
<!--    <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">-->
<!--        <property name="messageConverters">-->
<!--          <list>-->
<!--            <ref bean="stringHttpMessageConverter"/>-->
<!--          </list>-->
<!--        </property>-->
<!--    </bean>-->
</beans>

I'm testing this using curl as follows:

curl -d asd=123 -d qwe=456 http://localhost:8080/requestbody

Any ideas or help is more than welcomed!

Answer 1

Here is a code snippet of ServletServerHttpRequest, which extends HttpInputMessage. I am pretty positive this is the implementation that you are using in your code:

public InputStream getBody() throws IOException {
    return this.servletRequest.getInputStream();
}

In other words, the request body is meant to be read as the input stream of the HttpServletRequest object.

The request's input stream is not valid in several situations, but I can't find the correct documentation for it at the moment. For example, if you call request.getParameter() on a post request, tomcat has to read the input stream in order to interpret the parameters, thus afterwards when you read the input stream, it is empty because it has reached the end already.

Perhaps you are invoking getParameter somewhere in an interceptor or perhaps a filter defined in web.xml. Another option is that Spring is doing that for you, for example, if your controller has some other method with complex @RequestMappings (such as reading param values, or header values).

I have two suggestions for you:

1. Add a servlet filter (before spring gets a chance to act), and wrap the request with your own wrapper (just extend HttpServletRequestWrapper). This way you can put breakpoints or log messages at some methods of the request object and see who's calling them.

2. Use a pojo object parameter, and setup the bindings. It seems like a much cleaner way to read post data.