CompositeFilter.java

package com.mossle.core.servlet;

import java.io.IOException;

import java.util.ArrayList;
import java.util.List;

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

public class CompositeFilter implements Filter {
    private List<? extends Filter> filters = new ArrayList<Filter>();

    public void setFilters(List<? extends Filter> filters) {
        this.filters = new ArrayList<Filter>(filters);
    }

    public void destroy() {
        for (int i = filters.size(); i-- > 0;) {
            Filter filter = filters.get(i);
            filter.destroy();
        }
    }

    public void init(FilterConfig config) throws ServletException {
        for (Filter filter : filters) {
            filter.init(config);
        }
    }

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        new VirtualFilterChain(chain, filters).doFilter(request, response);
    }

    private static final class VirtualFilterChain implements FilterChain {
        private final FilterChain originalChain;
        private final List<? extends Filter> additionalFilters;
        private int currentPosition = 0;

        private VirtualFilterChain(FilterChain chain,
                List<? extends Filter> additionalFilters) {
            this.originalChain = chain;
            this.additionalFilters = additionalFilters;
        }

        public void doFilter(final ServletRequest request,
                final ServletResponse response) throws IOException,
                ServletException {
            if (currentPosition == additionalFilters.size()) {
                originalChain.doFilter(request, response);
            } else {
                currentPosition++;

                Filter nextFilter = additionalFilters.get(currentPosition - 1);
                nextFilter.doFilter(request, response, this);
            }
        }
    }
}