Example 7.12 Using a Template Filter Strategy

public abstract class TemplateFilter implements 
  javax.servlet.Filter {
  private FilterConfig filterConfig;

  public void setFilterConfig(FilterConfig fc) { 
    filterConfig=fc; 
  }

  public FilterConfig getFilterConfig() 	{ 
    return filterConfig; 
  }

  public void doFilter(ServletRequest request, 
    ServletResponse response, FilterChain chain)
    throws IOException, ServletException {
    // Common processing for all filters can go here 
    doPreProcessing(request, response, chain);

    // Common processing for all filters can go here
    doMainProcessing(request, response, chain);

    // Common processing for all filters can go here 
    doPostProcessing(request, response, chain);

    // Common processing for all filters can go here

    // Pass control to the next filter in the chain or 
    // to the target resource
    chain.doFilter(request, response);
  }
  public void doPreProcessing(ServletRequest request, 	
    ServletResponse response, FilterChain chain) {
  }

  public void doPostProcessing(ServletRequest request, 
    ServletResponse response, FilterChain chain) {
  }

  public abstract void doMainProcessing(ServletRequest 
   request, ServletResponse response, FilterChain 
   chain);
}