responsetimefilter.java

jsp 应用开发技术光盘 是《jsp应用开发技术》这本书的源代码

package ch17;

import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.*;

/**
 * 计算并记录请求的响应时间到日志文件
 */
public class ResponseTimeFilter implements Filter {

	protected FilterConfig config;

	public void init(FilterConfig filterConfig) throws ServletException {
		this.config = filterConfig;
	}

	// 需要重点实现的方法
	public void doFilter(
		ServletRequest request,
		ServletResponse response,
		FilterChain chain)
		throws IOException, ServletException {

		// 响应开始时间
		long startTime = System.currentTimeMillis();

		// 将请求转发给过滤器链上其他对象
		chain.doFilter(request, response);

		// 计算请求的响应时间
		long elapsed = System.currentTimeMillis() - startTime;

		String name = "default";
		if (request instanceof HttpServletRequest) {
			name = ((HttpServletRequest) request).getRequestURI();
		}

		// 将请求的响应时间记录到日志文件
		config.getServletContext().log(name + " took " + elapsed + " ms");

	}

	public void destroy() {

	}

}