Get the POST request body from HttpServletRequest

I am trying to get the whole body from the HttpServletRequest object.

The code I am following looks like this:

if ( request.getMethod().equals("POST") )
{
	StringBuffer sb = new StringBuffer();
	BufferedReader bufferedReader = null;
	String content = "";
	
	try {
		//InputStream inputStream = request.getInputStream();
		//inputStream.available();
		//if (inputStream != null) {
		bufferedReader =  request.getReader() ; //new BufferedReader(new InputStreamReader(inputStream));
		char[] charBuffer = new char[128];
		int bytesRead;
		while ( (bytesRead = bufferedReader.read(charBuffer)) != -1 ) {
			sb.append(charBuffer, 0, bytesRead);
		}
		//} else {
		//        sb.append("");
		//}
	
	} catch (IOException ex) {
		throw ex;
	} finally {
		if (bufferedReader != null) {
			try {
				bufferedReader.close();
			} catch (IOException ex) {
				throw ex;
			}
		}
	}
	
	test = sb.toString();
}

and I am testing the functionality with curl and wget as follows:

curl --header "MD5: abcd" -F "[email protected] http://localhost:8080/abcd.html"

wget --header="MD5: abcd" --post-data='{"imei":"351553012623446","hni":"310150","wdp":false}' http://localhost:8080/abcd.html"

But the while ( (bytesRead = bufferedReader.read(charBuffer)) != -1 ) does not return anything, and so I get nothing appended on StringBuffer.

In Java 8, you can do it in a simpler and clean way :

if ("POST".equalsIgnoreCase(request.getMethod())) 
{
   test = request.getReader().lines().collect(Collectors.joining(System.lineSeparator()));
}

Easy way with commons-io.

IOUtils.toString(request.getReader());

https://commons.apache.org/proper/commons-io/javadocs/api-2.5/org/apache/commons/io/IOUtils.html

Be aware, that your code is quite noisy. I know the thread is old, but a lot of people will read it anyway. You could do the same thing using the guava library with:

    if ("POST".equalsIgnoreCase(request.getMethod())) {
        test = CharStreams.toString(request.getReader());
    }

If all you want is the POST request body, you could use a method like this:

static String extractPostRequestBody(HttpServletRequest request) throws IOException {
    if ("POST".equalsIgnoreCase(request.getMethod())) {
        Scanner s = new Scanner(request.getInputStream(), "UTF-8").useDelimiter("\\A");
        return s.hasNext() ? s.next() : "";
    }
    return "";
}

Credit to: https://stackoverflow.com/a/5445161/1389219

This works for both GET and POST:

@Context
private HttpServletRequest httpRequest;


private void printRequest(HttpServletRequest httpRequest) {
	System.out.println(" \n\n Headers");

	Enumeration headerNames = httpRequest.getHeaderNames();
	while(headerNames.hasMoreElements()) {
		String headerName = (String)headerNames.nextElement();
		System.out.println(headerName + " = " + httpRequest.getHeader(headerName));
	}

	System.out.println("\n\nParameters");

	Enumeration params = httpRequest.getParameterNames();
	while(params.hasMoreElements()){
		String paramName = (String)params.nextElement();
		System.out.println(paramName + " = " + httpRequest.getParameter(paramName));
	}

	System.out.println("\n\n Row data");
	System.out.println(extractPostRequestBody(httpRequest));
}

static String extractPostRequestBody(HttpServletRequest request) {
	if ("POST".equalsIgnoreCase(request.getMethod())) {
		Scanner s = null;
		try {
			s = new Scanner(request.getInputStream(), "UTF-8").useDelimiter("\\A");
		} catch (IOException e) {
			e.printStackTrace();
		}
		return s.hasNext() ? s.next() : "";
	}
	return "";
}

If the request body is empty, then it simply means that it's already been consumed beforehand. For example, by a request.getParameter(), getParameterValues() or getParameterMap() call. Just remove the lines doing those calls from your code.

This will work for all HTTP method.

public class HttpRequestWrapper extends HttpServletRequestWrapper {
    private final String body;

    public HttpRequestWrapper(HttpServletRequest request) throws IOException {
        super(request);
        body = IOUtils.toString(request.getReader());
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(getBody().getBytes());
        ServletInputStream servletInputStream = new ServletInputStream() {
            public int read() throws IOException {
                return byteArrayInputStream.read();
            }

            @Override
            public boolean isFinished() {
                return false;
            }

            @Override
            public boolean isReady() {
                return false;
            }

            @Override
            public void setReadListener(ReadListener listener) {
            }

        };
        return servletInputStream;
    }

    public String getBody() {
        return this.body;
    }
}

Easiest way I could think of:

request.getReader().lines().reduce("",String::concat)

• However, this will be one long string which you will have to parse. IF you send a username of tim and a password of 12345. The output of the code above would look like this:

{    "username":"tim",    "password": "12345"}

Please be aware

• Please be aware that with the reduce() method we are performing a Mutable Reduction which does a great deal of string copying and has a runtime of O(N^2) with N being the number of characters. Please check the Mutable Reduction documentation if you need a more performant result.

I personnally use this code (on a dev server, not in production). Seems to work. The main difficulty is that once you read the request body, it will be lost and not transferred to the app. So you have to "cache" it first.

/* Export this filter as a jar and place it under directory ".../tomcat/lib" on your Tomcat server/
 In the lib directory, also place the dependencies you need
 (ex. org.apache.commons.io => commons-io-2.8.0.jar)
 
 Once this is done, in order to activate the filter, on the Tomcat server: 
 o in .../tomcat/conf/server.xml, add:
  <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log" suffix=".txt" pattern="%h %l %u %t &quot;%r&quot;  [%{postdata}r] %s %b"/>
  => the server will log the "postdata" attribute we generate in the Java code.
 o in .../tomcat/conf/web.xml, add:
  <filter>
  <filter-name>post-data-dumper-filter</filter-name>
  <filter-class>filters.PostDataDumperFilter</filter-class>
  </filter>
  <filter-mapping>
  <filter-name>post-data-dumper-filter</filter-name>
  <url-pattern>/*</url-pattern>
  </filter-mapping>

Once you've done this, restart your tomcat server. You will get extra infos in file "localhost_access_log.<date>.txt"

*/

package filters;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Enumeration;
import java.util.stream.Collectors;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

import org.apache.commons.io.IOUtils;

class MultiReadHttpServletRequest extends HttpServletRequestWrapper {
    private ByteArrayOutputStream cachedBytes;

    public MultiReadHttpServletRequest(HttpServletRequest request) {
        super(request);
    }

    @Override
    public ServletInputStream getInputStream() throws IOException {
        if (cachedBytes == null)
            cacheInputStream();

        return new CachedServletInputStream();
    }

    @Override
    public BufferedReader getReader() throws IOException {
        return new BufferedReader(new InputStreamReader(getInputStream()));
    }

    private void cacheInputStream() throws IOException {
        /* Cache the inputstream in order to read it multiple times.
         */
        cachedBytes = new ByteArrayOutputStream();
        IOUtils.copy(super.getInputStream(), cachedBytes);
    }

    /* An input stream which reads the cached request body */
    public class CachedServletInputStream extends ServletInputStream {
        private ByteArrayInputStream input;

        public CachedServletInputStream() {
            /* create a new input stream from the cached request body */
            input = new ByteArrayInputStream(cachedBytes.toByteArray());
        }
        //---------------------
        @Override
        public int read() throws IOException {
            return input.read();
        }

        @Override
        public boolean isFinished() {
            return input.available() == 0;
        }

        @Override
        public boolean isReady() {
            return true;
        }
        //---------------------
        @Override
        public void setReadListener(ReadListener arg0) {
            // TODO Auto-generated method stub
            // Ex. : throw new RuntimeException("Not implemented");
        }
    }
}

public final class PostDataDumperFilter implements Filter {

    private FilterConfig filterConfig = null;


    public void destroy() {
        this.filterConfig = null;
    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        if (filterConfig == null)
            return;

        StringBuffer output = new StringBuffer();
        output.append("PostDataDumperFilter-");

        /* Wrap the request in order to be able to read its body multiple times */
        MultiReadHttpServletRequest multiReadRequest = new MultiReadHttpServletRequest((HttpServletRequest) request);

        // TODO : test the method in order not to log the body when receiving GET/DELETE requests ?
        // I finally leave it "as it", since I've seen GET requests containing bodies (hell...).
        output.append("Content-type=" + multiReadRequest.getContentType());
        output.append(" - HTTP Method=" + multiReadRequest.getMethod());
        output.append(" - REQUEST BODY = " + multiReadRequest.getReader().lines().collect(Collectors.joining(System.lineSeparator())));


        // Log the request parameters:
        Enumeration names = multiReadRequest.getParameterNames();
        if (names.hasMoreElements()) {
            output.append("- REQUEST PARAMS = ");
        }

        while (names.hasMoreElements()) {
            String name = (String) names.nextElement();
            output.append(name + "=");
            String values[] = multiReadRequest.getParameterValues(name);
            for (int i = 0; i < values.length; i++) {
                if (i > 0) output.append("' ");
                output.append(values[i]);
            }
            if (names.hasMoreElements()) output.append("&");
        }

        multiReadRequest.setAttribute("postdata", output);
        chain.doFilter(multiReadRequest, response);
    }

    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
    }
}

I resolved that situation in this way. I created a util method that return a object extracted from request body, using the readValue method of ObjectMapper that is capable of receiving a Reader.

public static <T> T getBody(ResourceRequest request, Class<T> class) {
    T objectFromBody = null;
    try {
        ObjectMapper objectMapper = new ObjectMapper();
        HttpServletRequest httpServletRequest = PortalUtil.getHttpServletRequest(request);
        objectFromBody = objectMapper.readValue(httpServletRequest.getReader(), class);
    } catch (IOException ex) {
        log.error("Error message", ex);
    }
    return objectFromBody;
}