container/catalina/src/share/org/apache/catalina/filters/FailedRequestFilter.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.filters;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;

import org.apache.catalina.Globals;

/**
 * Filter that will reject requests if there was a failure during parameter
 * parsing. This filter can be used to ensure that none parameter values
 * submitted by client are lost.
 *
 * <p>
 * Note that it has side effect that it triggers parameter parsing and thus
 * consumes the body for POST requests. Parameter parsing does check content
 * type of the request, so there should not be problems with addresses that use
 * <code>request.getInputStream()</code> and <code>request.getReader()</code>,
 * if requests parsed by them do not use standard value for content mime-type.
 */
public class FailedRequestFilter implements Filter {

    public void init(FilterConfig filterConfig) {
        // NOOP
    }

    public void destroy() {
        // NOOP
    }

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        if (!isGoodRequest(request)) {
            ((HttpServletResponse) response)
                    .sendError(HttpServletResponse.SC_BAD_REQUEST);
            return;
        }
        chain.doFilter(request, response);
    }

    private boolean isGoodRequest(ServletRequest request) {
        // Trigger parsing of parameters
        request.getParameter("none");
        // Detect failure
        if (request.getAttribute(Globals.PARAMETER_PARSE_FAILED_ATTR) != null) {
            return false;
        }
        return true;
    }

}