ParamWrapperFilter.java

gistfile1.txt

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

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.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.List;
import java.util.regex.Pattern;

public class ParamWrapperFilter implements Filter {

    private Pattern pattern;

    private static Logger logger = LogManager.getLogger(ParamWrapperFilter.class);

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        pattern = Pattern.compile(filterConfig.getInitParameter("excludeParams"));
    }


    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        chain.doFilter(new ParamFilteredRequest(request, pattern), response);
    }

    @Override
    public void destroy() {
    }

    /** */
    private static class ParamFilteredRequest extends HttpServletRequestWrapper {

        private final Pattern pattern;

        ParamFilteredRequest(ServletRequest request, Pattern pattern) {
            super((HttpServletRequest)request);
            this.pattern = pattern;
        }

        @Override
        public Enumeration<String> getParameterNames() {
            List<String> requestParameterNames = Collections.list(super.getParameterNames());
            List<String> finalParameterNames = new ArrayList<>();

            for (String parameterName: requestParameterNames) {
                if (!pattern.matcher(parameterName).matches()) {
                    finalParameterNames.add(parameterName);
                } else {
                    logger.warn("parameters to exclude : {}", parameterName);
                }
            }
            return Collections.enumeration(finalParameterNames);
        }
    }
}