Why is HttpServletRequest inputstream empty?

Question

I have this code where I read the input from a request input stream and use a JacksonMapper to convert into a POJO. Its running in a jetty 7 container with guice support.

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    try {
        RequestType requestType = mapper.readValue(req.getInputStream(), RequestType.class);
    } Catch(Exception ex) {
        ....
    }
}

However, sometimes under load the following exception is thrown. I have checked my client and I am sure its sending a valid json string. What is going wrong? Is it expected behavior for Jetty 7 under load?

java.io.EOFException: No content to map to Object due to end of input
    at org.codehaus.jackson.map.ObjectMapper._initForReading(ObjectMapper.java:2433)
    at org.codehaus.jackson.map.ObjectMapper._readMapAndClose(ObjectMapper.java:2385)
    at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1637)
    at com.ea.wsop.user.LoginServlet.processRequest(LoginServlet.java:69)
    at com.ea.wsop.user.LoginServlet.doPost(LoginServlet.java:63)
    at com.ea.wsop.user.LoginServlet$$EnhancerByGuice$$a91c2ebd.CGLIB$doPost$0(<generated>)
    at com.ea.wsop.user.LoginServlet$$EnhancerByGuice$$a91c2ebd$$FastClassByGuice$$c6f479ee.invoke(<generated>)
    at com.google.inject.internal.cglib.proxy.$MethodProxy.invokeSuper(MethodProxy.java:228)
    at com.google.inject.internal.InterceptorStackCallback$InterceptedMethodInvocation.proceed(InterceptorStackCallback.java:72)
    at com.ea.monitor.MethodExecutionTimer.invoke(MethodExecutionTimer.java:130)
    at com.google.inject.internal.InterceptorStackCallback$InterceptedMethodInvocation.proceed(InterceptorStackCallback.java:72)
    at com.google.inject.internal.InterceptorStackCallback.intercept(InterceptorStackCallback.java:52)
    at com.ea.wsop.user.LoginServlet$$EnhancerByGuice$$a91c2ebd.doPost(<generated>)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at com.ea.wsop.user.LoginServlet$$EnhancerByGuice$$a91c2ebd.CGLIB$service$8(<generated>)
    at com.ea.wsop.user.LoginServlet$$EnhancerByGuice$$a91c2ebd$$FastClassByGuice$$c6f479ee.invoke(<generated>)
    at com.google.inject.internal.cglib.proxy.$MethodProxy.invokeSuper(MethodProxy.java:228)
    at com.google.inject.internal.InterceptorStackCallback$InterceptedMethodInvocation.proceed(InterceptorStackCallback.java:72)
    at com.ea.monitor.MethodExecutionTimer.invoke(MethodExecutionTimer.java:130)
    at com.google.inject.internal.InterceptorStackCallback$InterceptedMethodInvocation.proceed(InterceptorStackCallback.java:72)
    at com.google.inject.internal.InterceptorStackCallback.intercept(InterceptorStackCallback.java:52)
    at com.ea.wsop.user.LoginServlet$$EnhancerByGuice$$a91c2ebd.service(<generated>)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
    at com.ea.wsop.user.LoginServlet$$EnhancerByGuice$$a91c2ebd.CGLIB$service$9(<generated>)
    at com.ea.wsop.user.LoginServlet$$EnhancerByGuice$$a91c2ebd$$FastClassByGuice$$c6f479ee.invoke(<generated>)
    at com.google.inject.internal.cglib.proxy.$MethodProxy.invokeSuper(MethodProxy.java:228)
    at com.google.inject.internal.InterceptorStackCallback$InterceptedMethodInvocation.proceed(InterceptorStackCallback.java:72)
    at com.ea.monitor.MethodExecutionTimer.invoke(MethodExecutionTimer.java:130)
    at com.google.inject.internal.InterceptorStackCallback$InterceptedMethodInvocation.proceed(InterceptorStackCallback.java:72)
    at com.google.inject.internal.InterceptorStackCallback.intercept(InterceptorStackCallback.java:52)
    at com.ea.wsop.user.LoginServlet$$EnhancerByGuice$$a91c2ebd.service(<generated>)
    at com.google.inject.servlet.ServletDefinition.doService(ServletDefinition.java:263)

Answer 1

I had a similar problem running a Spring Boot application. My Spring Boot app is a simple Dispatcher servlet that reads the request body and processes it.

In my case, the client (curl) sets a content-type header of application/x-www-form-urlencoded if the curl command line uses -d {some-data} and does not set an specific content-type header via -Hcontent-type=some-other-media-type.

Inside the Apache Catalina servlet engine that Spring Boot runs, the Request class makes the following test in parseParameters()

        if (!("application/x-www-form-urlencoded".equals(contentType))) {
            success = true;
            return;
        }

For other content-type values, Request returns here, done.

However, if the content type matches application/x-www-form-urlencoded, Request continues:

    try {
       if (readPostBody(formData, len) != len) {           
            parameters.setParseFailedReason(FailReason.REQUEST_BODY_INCOMPLETE);
            return;
        }
    } catch (....)

which will consume the body. So in my case, even though my servlet does nothing other than call request.getInputStream() and try to read() from it, it is already too late - the runtime Request already reads the input and does not buffer or unread it. The only workaround is to set a different Content-Type.

The culprit is OrderedHiddenHttpMethodFilter(HiddenHttpMethodFilter).doFilterInternal(HttpServletRequest, HttpServletResponse, FilterChain) line 70

which is looking for the "_method" query parameter.

I was able to disable the filter by adding

@Bean
public FilterRegistrationBean registration(HiddenHttpMethodFilter filter) {
    FilterRegistrationBean registration = new FilterRegistrationBean(filter);
    registration.setEnabled(false);
    return registration;
}

(which was used to solve another problem)

Answer 2

It will be empty if it's already consumed beforehand. This will be implicitly done whenever you call getParameter(), getParameterValues(), getParameterMap(), getReader(), etc on the HttpServletRequest. Make sure that you don't call any of those kind of methods which by themselves need to gather information from the request body before calling getInputStream(). If your servlet isn't doing that, then start checking the servlet filters which are mapped on the same URL pattern.

---

Update: this seems to be GAE 1.5 specific. See also

• http://code.google.com/p/googleappengine/issues/detail?id=5161
• http://code.google.com/p/googleappengine/issues/detail?id=5898

I'm afraid that there's no solution/workaround until they get it fixed. You could try to check if it's available inside a Filter and if so, then copy and store it as request attribute. But this might affect further processing by some GAE servlet.