Welcome to the website of Davis Fiore

It's an object that can intercept and change requests or responses in a web application. For example, a servlet can generate a response and a filter can add http directives to it.

A filter is simply a class that implements the interface Filter and is configured into the web.xml:

    <filter>
        <filter-name>cacheFilter</filter-name>
            <filter-class>org.davis.filter.CacheFilter</filter-class>
        </filter>
        <filter-mapping>
            <filter-name>cacheFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

The above configuration can be replaced by an annotation into the filter itself:

	@WebFilter("/*")

To automatically generate a filter in Eclipse, select File->Other, then "filter" and follow the wizard. This is the output:

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

	/**
	 * Servlet Filter implementation class MyFilter
	 */
	public class MyFilter implements Filter {

		/**
		 * Default constructor. 
		 */
		public MyFilter() {
			// TODO Auto-generated constructor stub
		}

		/**
		 * @see Filter#destroy()
		 */
		public void destroy() {
			// TODO Auto-generated method stub
		}

		/**
		 * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
		 */
		public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
			// TODO Auto-generated method stub
			// place your code here

			// pass the request along the filter chain
			chain.doFilter(request, response);
		}

		/**
		 * @see Filter#init(FilterConfig)
		 */
		public void init(FilterConfig fConfig) throws ServletException {
			// TODO Auto-generated method stub
		}
	}

Common uses of filters are: checking if the user is logged-in, logging, data compression, data conversion etc.