使用servlet重定向请求并且“setHeader”方法不起作用
我是servlet开发的新手，我正在阅读一本电子书，发现我可以使用重定向到另一个网页
setHeader("Location", "http://www.google.com") 但这不起作用，因为我已将此代码编写为：
import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class ModHelloWorld extends HttpServlet{ public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException{ // response.addHeader("Location", "http://www.google.com"); response.setHeader("Location", "http://www.google.com"); response.setContentType("text/html"); PrintWriter pw = response.getWriter(); pw.println("Modified Hello World "); pw.println(""); //getInitParameter function reads the contents ot init-param elements. pw.println(getInitParameter("message")); pw.println("
"); pw.println(""); pw.close(); } }
我已经使用我的程序检查了标题以获取网页的标题，如下所示：
import java.net.*; import java.io.*; class getHeaders{ public static void main(String args[]){ URL url = null; URLConnection urc = null; try { url = new URL(args[0]); urc = url.openConnection(); for(int i=0 ; ; i++) { String name = urc.getHeaderFieldKey(i); String value = urc.getHeaderField(i); if(name == null && value == null)//both null so end of header break; else if(name == null){//first line of header{ System.out.println("Server HTTP version, Response code: "); System.out.println(value); System.out.println("ENd of first header field"); } else { System.out.println("name of header is: " + name + " and its value is : " + value); } } } catch(MalformedURLException e){ System.out.println("Malformed URL " + e.getMessage()); } catch(IOException e){ e.printStackTrace(); } } }
我得到的输出为：
Server HTTP version, Response code: HTTP/1.1 200 OK ENd of first header field name of header is: Server and its value is : Apache-Coyote/1.1 name of header is: Location and its value is : http://www.google.com name of header is: Content-Type and its value is : text/html name of header is: Content-Length and its value is : 101 name of header is: Date and its value is : Sat, 05 Mar 2011 15:27:29 GMT
但我没有从浏览器重定向到谷歌的页面。
提前致谢：）
如您所见，响应仍然是HTTP/1.1 200 OK 。 要指示重定向，您需要发回302状态代码：
response.setStatus(HttpServletResponse.SC_FOUND); // SC_FOUND = 302
哦不，不！ 这不是你重定向的方式。 它更简单：
public class ModHelloWorld extends HttpServlet{ public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException{ response.sendRedirect("http://www.google.com"); } }
此外，在servlet中编写HTML代码是一种不好的做法。 您应该考虑将所有标记放入JSP并使用以下方法调用JSP：
response.sendRedirect("/path/to/mynewpage.jsp");
如果要在指定的时间点之后重定向到任何url源，则执行此操作的另一种方法
import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.*; public class MyServlet extends HttpServlet { public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException { response.setContentType("text/html"); PrintWriter pw=response.getWriter(); pw.println("Redirecting to Google
"); response.setHeader("refresh,"5;https://www.google.com/"); // redirects to url after 5 seconds pw.close(); } }