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package filters;
import java.io.IOException;
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;
/**
* Example filter that can be attached to either an individual servlet
* or to a URL pattern. This filter performs the following functions:
* <ul>
* <li>Attaches itself as a request attribute, under the attribute name
* defined by the value of the <code>attribute</code> initialization
* parameter.</li>
* <li>Calculates the number of milliseconds required to perform the
* servlet processing required by this request, including any
* subsequently defined filters, and logs the result to the servlet
* context log for this application.
* </ul>
*
* @author Craig McClanahan
* @version $Revision: 1.3 $ $Date: 2007/05/05 05:34:22 $
*/
public final class ExampleFilter implements Filter {
// ----------------------------------------------------- Instance Variables
/**
* The request attribute name under which we store a reference to ourself.
*/
private String attribute = null;
/**
* The filter configuration object we are associated with. If this value
* is null, this filter instance is not currently configured.
*/
private FilterConfig filterConfig = null;
// --------------------------------------------------------- Public Methods
/**
* Take this filter out of service.
*/
public void destroy() {
this.attribute = null;
this.filterConfig = null;
}
/**
* Time the processing that is performed by all subsequent filters in the
* current filter stack, including the ultimately invoked servlet.
*
* @param request The servlet request we are processing
* @param result The servlet response we are creating
* @param chain The filter chain we are processing
*
* @exception IOException if an input/output error occurs
* @exception ServletException if a servlet error occurs
*/
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain)
throws IOException, ServletException {
// Store ourselves as a request attribute (if requested)
if (attribute != null)
request.setAttribute(attribute, this);
// Time and log the subsequent processing
long startTime = System.currentTimeMillis();
chain.doFilter(request, response);
long stopTime = System.currentTimeMillis();
filterConfig.getServletContext().log
(this.toString() + ": " + (stopTime - startTime) +
" milliseconds");
}
/**
* Place this filter into service.
*
* @param filterConfig The filter configuration object
*/
public void init(FilterConfig filterConfig) throws ServletException {
this.filterConfig = filterConfig;
this.attribute = filterConfig.getInitParameter("attribute");
}
/**
* Return a String representation of this object.
*/
public String toString() {
if (filterConfig == null)
return ("InvokerFilter()");
StringBuffer sb = new StringBuffer("InvokerFilter(");
sb.append(filterConfig);
sb.append(")");
return (sb.toString());
}
}
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