Filter Jersey request based on form data

Question

In Jersey 1.x, you can use ContainerRequest.getFormParameters() to do request filtering on the form data, but I don't see an obvious equivalent in Jersey 2.x. I've implemented the ContainerRequestFilter interface which gives me access to a ContainerRequestContext, but from there how can get the form data?

Jersey 1.x example:

public class MyFilter implements ContainerRequestFilter {
  public ContainerRequest filter(ContainerRequest request) {
    Form f = request.getFormParameters();

    // examine form data and filter as needed
  }
}

Jersey 2.x example:

public class MyFilter implements ContainerRequestFilter {
  public void filter(ContainerRequestContext context) {
    // how do I get to the Form data now?
  }
}

Answer 1

After a ton of searching and trial and error, I have found a suitable way to do this in Jersey 2. You have to consume the request entity body manually, but you have to be careful to do it in a way that doesn't prevent subsequent filters and resources from also consuming it. Below is a simple example that reads the entity into a Form object:

@Provider
public class FormDataFilter implements ContainerRequestFilter
{
    @Override
    public void filter(ContainerRequestContext requestContext) throws IOException
    {
        if (requestContext instanceof ContainerRequest)
        {
            ContainerRequest request = (ContainerRequest) requestContext;

            if ( requestContext.hasEntity()
              && MediaTypes.typeEqual(MediaType.APPLICATION_FORM_URLENCODED_TYPE,request.getMediaType()))
            {
                request.bufferEntity();
                Form f = request.readEntity(Form.class);
            }
        }
    } 
}

The key is calling bufferEntity(). Without this, the entity is marked as closed and causes IllegalStateExceptions on any subsequent read attempt.