/**
     * 2006-4-30
     * @author Sparkle
     */
    public abstract class ContentRewriteFilter implements Filter {
	protected boolean wantRewrite(HttpServletRequest request) {
		return true;
	}
 
	protected abstract String rewrite(String content,
			HttpServletRequest request, HttpServletResponse response);
 
	public void doFilter(ServletRequest req, ServletResponse res,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest) req;
		if (!wantRewrite(request) || res.isCommitted()) {
			chain.doFilter(req, res);
			return;
		}
 
		HttpServletResponse response = (HttpServletResponse) res;
		StringWriter strWriter = new StringWriter();
		boolean[] support = new boolean[1];
		support[0] = true;
		chain.doFilter(req, new ContentResponseWrapper(response, strWriter,
				support));
		if (support[0] && !response.isCommitted()) {
			String content = strWriter.getBuffer().toString();
 
			content = rewrite(content, request, response);
 
			PrintWriter printWriter = response.getWriter();
			printWriter.println(content);
			printWriter.close();
		}
 
	}
 
	public void destroy() {
	}
 
	public void init(FilterConfig config) throws ServletException {
	}
    }
 
 
    public class ContentResponseWrapper extends HttpServletResponseWrapper {
	private Writer writer;
 
	private boolean[] support;
 
	public ContentResponseWrapper(HttpServletResponse response, Writer writer,
			boolean[] support) {
		super(response);
		this.writer = writer;
		this.support = support;
	}
 
	@Override
	public ServletOutputStream getOutputStream() throws IOException {
		support[0] = false;
		return super.getOutputStream();
	}
 
	@Override
	public PrintWriter getWriter() throws IOException {
		return new PrintWriter(writer);
	}
 
    }