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 h

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.