FilterDecorator For tutorial

FilterDecorator

import java.io.IOException;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;

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

/**
 * Filter decorator class for CORSFilter so it can be used with DelegatinFilterProxy in Spring. 
 */
public class FilterDecoratorForSpring implements Filter{

    private final Filter decoratedFilter;

    private final DecoratedFilterConfig decoratedFilterConfig;

    public FilterDecoratorForSpring(final Filter decoratedFilter, final Map<String, String> configuration){
        super();
        this.decoratedFilter = decoratedFilter;
        this.decoratedFilterConfig = new DecoratedFilterConfig();

        for(final String key : configuration.keySet()){
            this.decoratedFilterConfig.addProperty(key, configuration.get(key));
        }
    }

    @Override
    public void init(final FilterConfig filterConfig) throws ServletException{
        this.decoratedFilterConfig.setServletContext(filterConfig.getServletContext());
        this.decoratedFilterConfig.setFilterName(filterConfig.getFilterName());
        this.decoratedFilter.init(filterConfig);
    }

    @Override
    public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain)
            throws IOException, ServletException{
        this.decoratedFilter.doFilter(request, response, chain);
    }

    @Override
    public void destroy(){
        this.decoratedFilter.destroy();
    }

    /**
     * Specific filterConfig implementation to be used by the CORS Filter
     */
    private static class DecoratedFilterConfig implements FilterConfig{

        private final Map<String, String> propertiesFilter = new HashMap<>();
        private String filterName;
        private ServletContext servletContext;

        @Override
        public String getFilterName(){
            return filterName;
        }

        @Override
        public ServletContext getServletContext(){
            return servletContext;
        }

        @Override
        public String getInitParameter(final String name){
            return propertiesFilter.get(name);
        }

        @Override
        public Enumeration<String> getInitParameterNames(){
            return null;
        }

        public void addProperty(final String key, final String value){
            this.propertiesFilter.put(key, value);
        }

        public void setFilterName(final String filterName){
            this.filterName = filterName;
        }

        public void setServletContext(final ServletContext servletContext){
            this.servletContext = servletContext;
        }
    }
}