Accessing the raw body of a PUT or POST request

It is possible by overriding the HttpServletRequest in a Servlet Filter.

You need to implement a HttpServletRequestWrapper that stores the request body:
src/java/grails/util/http/MultiReadHttpServletRequest.java

package grails.util.http;

import org.apache.commons.io.IOUtils;

import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.ServletInputStream;
import java.io.*;
import java.util.concurrent.atomic.AtomicBoolean;

public class MultiReadHttpServletRequest extends HttpServletRequestWrapper {

    private byte[] body;

    public MultiReadHttpServletRequest(HttpServletRequest httpServletRequest) {
        super(httpServletRequest);
        // Read the request body and save it as a byte array
        InputStream is = super.getInputStream();
        body = IOUtils.toByteArray(is);
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        return new ServletInputStreamImpl(new ByteArrayInputStream(body));
    }

    @Override
    public BufferedReader getReader() throws IOException {
        String enc = getCharacterEncoding();
        if(enc == null) enc = "UTF-8";
        return new BufferedReader(new InputStreamReader(getInputStream(), enc));
    }

    private class ServletInputStreamImpl extends ServletInputStream {

        private InputStream is;

        public ServletInputStreamImpl(InputStream is) {
            this.is = is;
        }

        public int read() throws IOException {
            return is.read();
        }

        public boolean markSupported() {
            return false;
        }

        public synchronized void mark(int i) {
            throw new RuntimeException(new IOException("mark/reset not supported"));
        }

        public synchronized void reset() throws IOException {
            throw new IOException("mark/reset not supported");
        }
    }

}

A Servlet Filter that overrides the current servletRequest: src/java/grails/util/http/MultiReadServletFilter.java

package grails.util.http;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
import java.util.Set;
import java.util.TreeSet;

public class MultiReadServletFilter implements Filter {

    private static final Set<String> MULTI_READ_HTTP_METHODS = new TreeSet<String>(String.CASE_INSENSITIVE_ORDER) {{
        // Enable Multi-Read for PUT and POST requests
            add("PUT");
            add("POST");
    }};

    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        if(servletRequest instanceof HttpServletRequest) {
            HttpServletRequest request = (HttpServletRequest) servletRequest;
            // Check wether the current request needs to be able to support the body to be read multiple times
            if(MULTI_READ_HTTP_METHODS.contains(request.getMethod())) {
                // Override current HttpServletRequest with custom implementation
                filterChain.doFilter(new MultiReadHttpServletRequest(request), servletResponse);
                return;
            }
        }
        filterChain.doFilter(servletRequest, servletResponse);
    }

    public void init(FilterConfig filterConfig) throws ServletException {
    }

    public void destroy() {
    }
}

Then you need to run grails install-templates and edit the web.xml in src/templates/war and add this after the charEncodingFilter definition:

<filter>
    <filter-name>multireadFilter</filter-name>
    <filter-class>grails.util.http.MultiReadServletFilter</filter-class>
</filter>

<filter-mapping>
    <filter-name>multireadFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

You should then be able to call request.inputStream as often as you need.

I haven’t tested this concrete code/procedure but I’ve done similar things in the past, so it should work 😉

Note: be aware that huge requests can kill your application (OutOfMemory…)