input stream copy

gistfile1.txt

/**
 * Class which is used to wrap a request in order that the wrapped request's input stream can be 
 * read once and later be read again in a pseudo fashion by virtue of keeping the original payload
 * as a string which is actually what is returned by subsequent calls to getInputStream().
 */
public class AuthenticationRequestWrapper 
    extends HttpServletRequestWrapper {
    
    private static Logger log = Logger.getLogger(AuthenticationRequestWrapper.class.getName());
 
    private final String xmlPayload;
    
    public AuthenticationRequestWrapper (HttpServletRequest request) 
        throws AuthenticationException {
        
        super(request);
        
        // read the original payload into the xmlPayload variable
        StringBuilder stringBuilder = new StringBuilder();
        BufferedReader bufferedReader = null;
        try {
            // read the payload into the StringBuilder
            InputStream inputStream = request.getInputStream();
            if (inputStream != null) {
                bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                char[] charBuffer = new char[128];
                int bytesRead = -1;
                while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
                    stringBuilder.append(charBuffer, 0, bytesRead);
                }
            } else {
                // make an empty string since there is no payload
                stringBuilder.append("");
            }
        } catch (IOException ex) {
            log.error("Error reading the request payload", ex);
            throw new AuthenticationException("Error reading the request payload", ex);
        } finally {
            if (bufferedReader != null) {
                try {
                    bufferedReader.close();
                } catch (IOException iox) {
                    // ignore
                }
            }
        }
        xmlPayload = stringBuilder.toString();
    }
 
    /**
     * Override of the getInputStream() method which returns an InputStream that reads from the
     * stored XML payload string instead of from the request's actual InputStream.
     */
    @Override
    public ServletInputStream getInputStream ()
        throws IOException {
        
        final ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(xmlPayload.getBytes());
        ServletInputStream inputStream = new ServletInputStream() {
            public int read () 
                throws IOException {
                return byteArrayInputStream.read();
            }
        };
        return inputStream;
    }
    
}


 public void doFilter (ServletRequest servletRequest,   
                          ServletResponse servletResponse,   
                          FilterChain filterChain)  
        throws IOException, ServletException {  
              
        // perform request filtering  
        HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;  
        AuthenticationRequestWrapper authenticationRequestWrapper;  
        try {  
            authenticationRequestWrapper = new AuthenticationRequestWrapper(httpServletRequest);              
        } catch (AuthenticationException ex) {  
            log.warn("Unable to wrap the request", ex);  
            throw new ServletException("Unable to wrap the request", ex);              
        }  
        try {  
            requestAuthenticator.authenticateRequest(authenticationRequestWrapper);  
        } catch (Exception ex) {  
            log.warn("Invalid request", ex);  
            throw new ServletException("Invalid request", ex);  
        }  
          
        // continue the filter chain  
        filterChain.doFilter(authenticationRequestWrapper, servletResponse);  
          
        // perform response filtering  
    }