Измените тело HttpServletRequest

Вы могли записать свой собственный Фильтр Сервлета и надо надеяться удостовериться, что это кажется первым в цепочке. Затем перенесите объект ServletRequest во что-то, что обработает перезапись при необходимости. Взгляните на раздел Programming Customized Requests и Responses http://java.sun.com/products/servlet/Filters.html

------Обновление------

Я должен пропускать что-то. Вы говорите, что можно считать тело запроса и считать параметры сами. Вы не могли затем удостовериться, что Ваш фильтр является первым, перенесите объект ServletRequest, считайте, обработайте и сохраните параметры, передайте свой запрос, возражают цепочке и предлагают параметры, которые Вы сохранили вместо исходных?

Вместо методов переопределения, почему Вы не устанавливаете фильтр сервлета, который переписывает запрос?

У Jason Hunter есть довольно хорошая статья о фильтрах.

Я сделал более полную оболочку, которая позволяет вам по-прежнему получать доступ к содержимому в случае, если Content-Type application / x-www-form-urlencoded, и вы уже вызвали один из методов getParameterXXX:

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;  
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.security.Principal;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Locale;
import java.util.Map;
import java.util.StringTokenizer;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletInputStream;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

/**
 * This class implements the Wrapper or Decorator pattern.<br/> 
 * Methods default to calling through to the wrapped request object, 
 * except the ones that read the request's content (parameters, stream or reader).
 * <p>
 * This class provides a buffered content reading that allows the methods
 * {@link #getReader()}, {@link #getInputStream()} and any of the getParameterXXX to be     called
 * safely and repeatedly with the same results.
 * <p>
 * This class is intended to wrap relatively small HttpServletRequest instances.
 * 
 * @author pgurov
 */
public class HttpServletRequestWrapper implements HttpServletRequest {

private class ServletInputStreamWrapper extends ServletInputStream {

    private byte[] data;
    private int idx = 0;
    ServletInputStreamWrapper(byte[] data) {
        if(data == null)
            data = new byte[0];
        this.data = data;
    }
    @Override
    public int read() throws IOException {
        if(idx == data.length)
            return -1;
        return data[idx++];
    }

}

private HttpServletRequest req;
private byte[] contentData;
private HashMap<String, String[]> parameters;

public HttpServletRequestWrapper() {
    //a trick for Groovy
    throw new IllegalArgumentException("Please use HttpServletRequestWrapper(HttpServletRequest request) constructor!");
}

private HttpServletRequestWrapper(HttpServletRequest request, byte[] contentData, HashMap<String, String[]> parameters) {
    req = request;
    this.contentData = contentData;
    this.parameters = parameters;
}

public HttpServletRequestWrapper(HttpServletRequest request) {
    if(request == null)
        throw new IllegalArgumentException("The HttpServletRequest is null!");
    req = request;
}

/**
 * Returns the wrapped HttpServletRequest.
 * Using the getParameterXXX(), getInputStream() or getReader() methods may interfere
 * with this class operation.
 * 
 * @return 
 *      The wrapped HttpServletRequest.
 */
public HttpServletRequest getRequest() {
    try {
        parseRequest();
    } catch (IOException e) {
        throw new IllegalStateException("Cannot parse the request!", e);
    }
    return new HttpServletRequestWrapper(req, contentData, parameters);
}

/**
 * This method is safe to use multiple times.
 * Changing the returned array will not interfere with this class operation.
 * 
 * @return 
 *      The cloned content data.
 */
public byte[] getContentData() {
    return contentData.clone();
}

/**
 * This method is safe to use multiple times.
 * Changing the returned map or the array of any of the map's values will not
 * interfere with this class operation.
 * 
 * @return
 *      The clonned parameters map.
 */
public HashMap<String, String[]> getParameters() {
    HashMap<String, String[]> map = new HashMap<String, String[]>(parameters.size() * 2);
    for(String key : parameters.keySet()) {
        map.put(key, parameters.get(key).clone());
    }
    return map;
}

private void parseRequest() throws IOException {
    if(contentData != null)
        return; //already parsed

    byte[] data = new byte[req.getContentLength()];
    int len = 0, totalLen = 0;
    InputStream is = req.getInputStream();
    while(totalLen < data.length) {
        totalLen += (len = is.read(data, totalLen, data.length - totalLen));
        if(len < 1)
            throw new IOException("Cannot read more than " + totalLen + (totalLen == 1 ? " byte!" : " bytes!"));
    }
    contentData = data;
    String enc = req.getCharacterEncoding();
    if(enc == null)
        enc = "UTF-8";
    String s = new String(data, enc), name, value;
    StringTokenizer st = new StringTokenizer(s, "&");
    int i;
    HashMap<String, LinkedList<String>> mapA = new HashMap<String, LinkedList<String>>(data.length * 2);
    LinkedList<String> list;
    boolean decode = req.getContentType() != null && req.getContentType().equals("application/x-www-form-urlencoded");
    while(st.hasMoreTokens()) {
        s = st.nextToken();
        i = s.indexOf("=");
        if(i > 0 && s.length() > i + 1) {
            name = s.substring(0, i);
            value = s.substring(i+1);
            if(decode) {
                try {
                    name = URLDecoder.decode(name, "UTF-8");
                } catch(Exception e) {}
                try {
                    value = URLDecoder.decode(value, "UTF-8");
                } catch(Exception e) {}
            }
            list = mapA.get(name);
            if(list == null) {
                list = new LinkedList<String>();
                mapA.put(name, list);
            }
            list.add(value);
        }
    }
    HashMap<String, String[]> map = new HashMap<String, String[]>(mapA.size() * 2);
    for(String key : mapA.keySet()) {
        list = mapA.get(key);
        map.put(key, list.toArray(new String[list.size()]));
    }
    parameters = map;
}

/**
 * This method is safe to call multiple times.
 * Calling it will not interfere with getParameterXXX() or getReader().
 * Every time a new ServletInputStream is returned that reads data from the begining.
 * 
 * @return
 *      A new ServletInputStream.
 */
public ServletInputStream getInputStream() throws IOException {
    parseRequest();

    return new ServletInputStreamWrapper(contentData);
}

/**
 * This method is safe to call multiple times.
 * Calling it will not interfere with getParameterXXX() or getInputStream().
 * Every time a new BufferedReader is returned that reads data from the begining.
 * 
 * @return
 *      A new BufferedReader with the wrapped request's character encoding (or UTF-8 if null).
 */
public BufferedReader getReader() throws IOException {
    parseRequest();

    String enc = req.getCharacterEncoding();
    if(enc == null)
        enc = "UTF-8";
    return new BufferedReader(new InputStreamReader(new ByteArrayInputStream(contentData), enc));
}

/**
 * This method is safe to execute multiple times.
 * 
 * @see javax.servlet.ServletRequest#getParameter(java.lang.String)
 */
public String getParameter(String name) {
    try {
        parseRequest();
    } catch (IOException e) {
        throw new IllegalStateException("Cannot parse the request!", e);
    }
    String[] values = parameters.get(name);
    if(values == null || values.length == 0)
        return null;
    return values[0];
}

/**
 * This method is safe.
 * 
 * @see {@link #getParameters()}
 * @see javax.servlet.ServletRequest#getParameterMap()
 */
@SuppressWarnings("unchecked")
public Map getParameterMap() {
    try {
        parseRequest();
    } catch (IOException e) {
        throw new IllegalStateException("Cannot parse the request!", e);
    }
    return getParameters();
}

/**
 * This method is safe to execute multiple times.
 * 
 * @see javax.servlet.ServletRequest#getParameterNames()
 */
@SuppressWarnings("unchecked")
public Enumeration getParameterNames() {
    try {
        parseRequest();
    } catch (IOException e) {
        throw new IllegalStateException("Cannot parse the request!", e);
    }
    return new Enumeration<String>() {
        private String[] arr = getParameters().keySet().toArray(new String[0]); 
        private int idx = 0;

        public boolean hasMoreElements() {
            return idx < arr.length;
        }

        public String nextElement() {
            return arr[idx++];
        }

    };
}

/**
 * This method is safe to execute multiple times.
 * Changing the returned array will not interfere with this class operation.
 * 
 * @see javax.servlet.ServletRequest#getParameterValues(java.lang.String)
 */
public String[] getParameterValues(String name) {
    try {
        parseRequest();
    } catch (IOException e) {
        throw new IllegalStateException("Cannot parse the request!", e);
    }
    String[] arr = parameters.get(name);
    if(arr == null)
        return null;
    return arr.clone();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getAuthType()
 */
public String getAuthType() {
    return req.getAuthType();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getContextPath()
 */
public String getContextPath() {
    return req.getContextPath();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getCookies()
 */
public Cookie[] getCookies() {
    return req.getCookies();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getDateHeader(java.lang.String)
 */
public long getDateHeader(String name) {
    return req.getDateHeader(name);
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getHeader(java.lang.String)
 */
public String getHeader(String name) {
    return req.getHeader(name);
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getHeaderNames()
 */
@SuppressWarnings("unchecked")
public Enumeration getHeaderNames() {
    return req.getHeaderNames();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getHeaders(java.lang.String)
 */
@SuppressWarnings("unchecked")
public Enumeration getHeaders(String name) {
    return req.getHeaders(name);
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getIntHeader(java.lang.String)
 */
public int getIntHeader(String name) {
    return req.getIntHeader(name);
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getMethod()
 */
public String getMethod() {
    return req.getMethod();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getPathInfo()
 */
public String getPathInfo() {
    return req.getPathInfo();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getPathTranslated()
 */
public String getPathTranslated() {
    return req.getPathTranslated();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getQueryString()
 */
public String getQueryString() {
    return req.getQueryString();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getRemoteUser()
 */
public String getRemoteUser() {
    return req.getRemoteUser();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getRequestURI()
 */
public String getRequestURI() {
    return req.getRequestURI();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getRequestURL()
 */
public StringBuffer getRequestURL() {
    return req.getRequestURL();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getRequestedSessionId()
 */
public String getRequestedSessionId() {
    return req.getRequestedSessionId();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getServletPath()
 */
public String getServletPath() {
    return req.getServletPath();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getSession()
 */
public HttpSession getSession() {
    return req.getSession();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getSession(boolean)
 */
public HttpSession getSession(boolean create) {
    return req.getSession(create);
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#getUserPrincipal()
 */
public Principal getUserPrincipal() {
    return req.getUserPrincipal();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#isRequestedSessionIdFromCookie()
 */
public boolean isRequestedSessionIdFromCookie() {
    return req.isRequestedSessionIdFromCookie();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#isRequestedSessionIdFromURL()
 */
public boolean isRequestedSessionIdFromURL() {
    return req.isRequestedSessionIdFromURL();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#isRequestedSessionIdFromUrl()
 */
@SuppressWarnings("deprecation")
public boolean isRequestedSessionIdFromUrl() {
    return req.isRequestedSessionIdFromUrl();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#isRequestedSessionIdValid()
 */
public boolean isRequestedSessionIdValid() {
    return req.isRequestedSessionIdValid();
}

/* (non-Javadoc)
 * @see javax.servlet.http.HttpServletRequest#isUserInRole(java.lang.String)
 */
public boolean isUserInRole(String role) {
    return req.isUserInRole(role);
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getAttribute(java.lang.String)
 */
public Object getAttribute(String name) {
    return req.getAttribute(name);
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getAttributeNames()
 */
@SuppressWarnings("unchecked")
public Enumeration getAttributeNames() {
    return req.getAttributeNames();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getCharacterEncoding()
 */
public String getCharacterEncoding() {
    return req.getCharacterEncoding();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getContentLength()
 */
public int getContentLength() {
    return req.getContentLength();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getContentType()
 */
public String getContentType() {
    return req.getContentType();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getLocalAddr()
 */
public String getLocalAddr() {
    return req.getLocalAddr();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getLocalName()
 */
public String getLocalName() {
    return req.getLocalName();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getLocalPort()
 */
public int getLocalPort() {
    return req.getLocalPort();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getLocale()
 */
public Locale getLocale() {
    return req.getLocale();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getLocales()
 */
@SuppressWarnings("unchecked")
public Enumeration getLocales() {
    return req.getLocales();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getProtocol()
 */
public String getProtocol() {
    return req.getProtocol();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getRealPath(java.lang.String)
 */
@SuppressWarnings("deprecation")
public String getRealPath(String path) {
    return req.getRealPath(path);
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getRemoteAddr()
 */
public String getRemoteAddr() {
    return req.getRemoteAddr();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getRemoteHost()
 */
public String getRemoteHost() {
    return req.getRemoteHost();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getRemotePort()
 */
public int getRemotePort() {
    return req.getRemotePort();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getRequestDispatcher(java.lang.String)
 */
public RequestDispatcher getRequestDispatcher(String path) {
    return req.getRequestDispatcher(path);
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getScheme()
 */
public String getScheme() {
    return req.getScheme();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getServerName()
 */
public String getServerName() {
    return req.getServerName();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#getServerPort()
 */
public int getServerPort() {
    return req.getServerPort();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#isSecure()
 */
public boolean isSecure() {
    return req.isSecure();
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#removeAttribute(java.lang.String)
 */
public void removeAttribute(String name) {
    req.removeAttribute(name);
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#setAttribute(java.lang.String, java.lang.Object)
 */
public void setAttribute(String name, Object value) {
    req.setAttribute(name, value);
}

/* (non-Javadoc)
 * @see javax.servlet.ServletRequest#setCharacterEncoding(java.lang.String)
 */
public void setCharacterEncoding(String env)
        throws UnsupportedEncodingException {
    req.setCharacterEncoding(env);
}

}