ex6_12.txt

j2ee core design patterns

Example 6.12 Using a Template Filter Strategy
public abstract class TemplateFilter implements javax.servlet.Filter {
  private FilterConfig filterConfig;
  public void init(FilterConfig filterConfig) throws ServletException {
    this.filterConfig = filterConfig;
  }

  protected FilterConfig getFilterConfig() 	{ 
    return filterConfig; 
  }

  public void doFilter(ServletRequest request, 
      ServletResponse response, FilterChain chain)
      throws IOException, ServletException {

    // Preprocessing for each filter 
    doPreProcessing(request, response);

    // Pass control to the next filter in the chain or 
    // to the target resource. This method invocation is what logically
    // demarcates preprocessing from postprocessing.
    chain.doFilter(request, response);

    // Post-processing for each filter
    doPostProcessing(request, response);
  }
  public abstract void doPreProcessing(ServletRequest request, 
      ServletResponse response) { }

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

  public void destroy() { }
}