一、jsp代碼

String chart1URL = c.makeSession(request, "chart1");

<img src='<%=response.encodeURL("getchart.jsp?"+chart1URL)%>'   usemap="#map1" border="0">

二、過濾器代碼

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

HttpServletRequest req=(HttpServletRequest)request;

HttpServletResponse resp=(HttpServletResponse)response;

HttpSession session=req.getSession(true);

resp.setContentType("text/html");

resp.setCharacterEncoding("UTF-8");

PrintWriter out=resp.getWriter();

String request_uri=req.getRequestURI();

String ctxPath=req.getContextPath();

String uri=request_uri.substring(ctxPath.length());

if(uri.contains("Login.jsp")||uri.contains("Login")||uri.contains("getchart")||uri.contains(".png")||uri.contains(".jpg")||uri.contains(".css")||uri.contains(".js")||uri.contains("testchart.jsp")) {

chain.doFilter(request, response);

}else {

if(null !=session.getAttribute("user")) {

chain.doFilter(request, response);

}else {

out.println("您還沒有登錄，請先登錄！3秒后回到登錄頁面。");

resp.setHeader("refresh","3;url="+ctxPath+"/Login.jsp");

return;

}

}

}

三、問題

無過濾器，顯示正常，上了過濾器后網頁不出圖。