解答例 - 実習課題1 - ６．フィルタ

（実習課題１）

サンプルのフィルタを実装し、５章実習課題３のサーブレットに適応する事。

解答例

/*
 * CounterFilter.java TECHSCORE Java Servlet6章 実習課題1
 * 
 * Copyright (c) 2004 Four-Dimensional Data, Inc.
 */
package com.techscore.servlet.chapter6.exercise1;

import java.io.IOException;
import java.io.PrintWriter;

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;
import javax.servlet.http.HttpServletResponse;

public class CounterFilter implements Filter {
    private ServletContext context = null;

    public void init(FilterConfig config) throws ServletException {
        context = config.getServletContext();
        context.setAttribute("counter", new Integer(1));
    }

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        chain.doFilter(request, response);
        Integer counter = (Integer) context.getAttribute("counter");
        PrintWriter writer = ((HttpServletResponse) response).getWriter();
        writer.print("フィルタのカウンタ:");
        writer.println(counter.intValue());
        context.setAttribute("counter", new Integer(counter.intValue() + 1));
    }

    public void destroy() {
        context = null;
    }

}

<?xml version="1.0" encoding="Shift_JIS"?>
<!DOCTYPE web-app
  PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
  "http://java.sun.com/dtd/web-app_2_3.dtd">

<web-app>
  <filter>
    <filter-name>Counter</filter-name>
    <filter-class>com.techscore.servlet.chapter6.exercise1.CounterFilter</filter-class>
  </filter>

  <filter-mapping>
    <filter-name>Counter</filter-name>
    <url-pattern>/servlet5-3</url-pattern>
  </filter-mapping>
  
</web-app>