一、HTTP中常用响应头
- Location: http://www.it315.org/index.jsp
- Server:apache tomcat
- Content-Encoding: gzip
- Content-Length: 80
- Content-Language: zh-cn
- Content-Type: text/html; charset=GB2312
- Last-Modified: Tue, 11 Jul 2000 18:23:51 GMT
- Refresh: 1;url=http://www.it315.org
- Content-Disposition: attachment; filename=aaa.zip
- Transfer-Encoding: chunked
- Set-Cookie:SS=Q0=5Lb_nQ; path=/search
- ETag: W/"7777-1242234904000"
- Expires: -1
- Cache-Control: no-cache
- Pragma: no-cache
- Connection: close/Keep-Alive
- Date: Tue, 11 Jul 2000 18:23:51 GMT
二、设置缓存信息
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
System.out.println("-----------CacheServlet-------------");
// 设置相应头信息
// 设置缓存时间100秒
// response.setDateHeader("Expires",
// System.currentTimeMillis()+100*1000);
// 禁止使用缓存
// response.setDateHeader("Expires", 0);
// response.setHeader("Cache-Control", "no-cache");
// response.setHeader("Pragma", "no-cache");
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
out.println("<HTML>");
out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
out.println(" <BODY>");
// 读取文件
String path = getServletContext().getRealPath("/a.txt");
FileReader reader = new FileReader(new File(path));
char buffer[] = new char[256];
int len = 0;
while ((len = reader.read(buffer)) != -1) {
out.println(new String(buffer, 0, len));
}
reader.close();
out.println(" </BODY>");
out.println("</HTML>");
out.flush();
out.close();
}
/**
* 最后一次修改的时间
*/
@Override
protected long getLastModified(HttpServletRequest req) {
String path = getServletContext().getRealPath("/a.txt");
File file = new File(path);
return file.lastModified();
}
a.txt文件内容：
a.txt在项目中的放置地址：
结果：
三、下载功能源代码如下
public class DownServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String path = request.getServletContext().getRealPath("/down/中国.png");
File file = new File(path);
// 下载的方式打开此操作（指定编码方式，下载文件名与源文件一致）
response.addHeader("Content-Disposition", "attachment;fileName="
+ URLEncoder.encode(file.getName(), "UTF-8"));
OutputStream os = response.getOutputStream();
InputStream is = new FileInputStream(file);
int len = 0;
byte[] buffer = new byte[1024];
while ((len = is.read(buffer)) != -1) {
os.write(buffer, 0, len);
}
is.close();
os.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
本程序中下载文件的地址放置在该项目的如下位置：