如何根据数据库字段动态的生成一个页面？
根据数据库字段动态的生成一个页面，利用Filter和定制Response，把服务器返回的JSP响应输出到我们自己的Response中，就可以将响应快速写入Html文件，然后再发送给客户。
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.Calendar;
public class CacheFilter implements Filter {
ServletContext sc;
FilterConfig fc;
long cacheTimeout = Long.MAX_VALUE;
public void doFilter(ServletRequest req,
ServletResponse res,
FilterChain chain)
throws IOException, ServletException {
HttpServletRequest request =
(HttpServletRequest) req;
HttpServletResponse response =
(HttpServletResponse) res;
// check if was a resource that shouldn't be cached.
String r = sc.getRealPath("");
String path =
fc.getInitParameter(request.getRequestURI());
if (path!= null && path.equals("nocache")) {
chain.doFilter(request, response);
return;
}
path = r+path;
String id = request.getRequestURI() +
request.getQueryString();
File tempDir = (File)sc.getAttribute(
"javax.servlet.context.tempdir");
// get possible cache
String temp = tempDir.getAbsolutePath();
File file = new File(temp+id);
// get current resource
if (path == null) {
path = sc.getRealPath(request.getRequestURI());
}
File current = new File(path);
try {
long now =
Calendar.getInstance().getTimeInMillis();
//set timestamp check
if (!file.exists() || (file.exists() &&
current.lastModified() > file.lastModified()) ||
cacheTimeout < now - file.lastModified()) {
String name = file.getAbsolutePath();
name =
name.substring(0,name.lastIndexOf("/"));
new File(name).mkdirs();
ByteArrayOutputStream baos =
new ByteArrayOutputStream();
CacheResponseWrapper wrappedResponse =
new CacheResponseWrapper(response, baos);
chain.doFilter(req, wrappedResponse);
FileOutputStream fos = new FileOutputStream(file);
fos.write(baos.toByteArray());
fos.flush();
fos.close();
}
} catch (ServletException e) {
if (!file.exists()) {
throw new ServletException(e);
}
}
catch (IOException e) {
if (!file.exists()) {
throw e;
}
}
FileInputStream fis = new FileInputStream(file);
String mt = sc.getMimeType(request.getRequestURI());
response.setContentType(mt);
ServletOutputStream sos = res.getOutputStream();
for (int i = fis.read(); i!= -1; i = fis.read()) {
sos.write((byte)i);
}
}
public void init(FilterConfig filterConfig) {
this.fc = filterConfig;
String ct =
fc.getInitParameter("cacheTimeout");
if (ct != null) {
cacheTimeout = 60*1000*Long.parseLong(ct);
}
this.sc = filterConfig.getServletContext();
}
public void destroy() {
this.sc = null;
this.fc = null;
}
}
